Officers of

The Arboretum Foundation

Mary Thome President Vice Presidents:

Bill MacKay Administration Janet Patrick Unit Council Mary Booth Special Events Duane Kelly Long-Range Planning Cecilia Buck Secretary Keith Patrick Treasurer Richard Doss Immediate Past President Rae Tennyson Executive Secretary Pamela Tharl Bookkeeper

Editorial Board of the Arboretum Bulletin Jan M. Silver Editor Jerry Clark

Jeannine Curry, Secretary Kelly Dodson Valerie Easton,

Book Review Editor Timothy Hohn Steven R. Lorton Virginia Morell Brian O. Mulligan Jan Pirzio-Biroli Sarah Hayden Reichard Mary Robson Barbara Swift Matsuo Tsukada, Ph.D.

Harold B. Tukey, Jr., Ph.D.

Richard Walker, Ph.D.

Advertising Director

Susie Marglin (206) 325-4510

Center for Urban Horticulture

Harold B. Tukey, Jr., Ph.D.

Director of Arboreta Brian O. Mulligan Director Emeritus The Washington Park Arboretum Timothy Hohn Curator, Plant Collections John A. Wott, Ph.D.

Professor

Continuing Education Lynda J. Ransley Coordinator

Printed on recycled gloss-coated paper (minimum 50% waste paper)

Concerning This Issue . . .

The seasons, when measured by pages tom off a Gary Larson desk calendar, have come full circle to winter. The view to the water has opened up from my perch in the Arboretum and I daydream about the houses I’ve been looking at to buy. One of my favorites can only accommodate a garden so small that with glue on the back it would be a postage stamp.

Gardeners everywhere are contemplating both the pleasures and challenges of the winter season. Some peo- ple will hibernate. Others may fly the coop. Before settling in or taking off, you can prepare the “coop” against winter’s harsher side. On these pages, we address con- cerns about safekeeping your garden, as well as enjoying winter’s beauty.

British author Rosemary Verey is associated with the garden in winter. Steven Lorton, Northwest Editor oi Sun- set Magazine , profiles Verey, highlighting both her estate and her “seasoned” philosophy.

With the change of seasons, we’ve watched our new editorial board member, Jan Pirzio-Biroli, come full circle in her career. This former editor of the Bulletin has cycled from volunteer to professional naturalist, back into alleged retirement — again as an Arboretum Foundation volun- teer. Jan’s article on winter in the Arboretum leads us boldly through the subtleties of the season, making winter’s nuances exciting.

How did the Arboretum actually fare last winter? Cura- tor Timothy Hohn reports on its trials and tribulations in his winter column. Three of Washington State Univer- sity’s cooperative extension professionals also team up to offer advice on preparing for this current winter season: Ray Maleike helps us prepare for winter cold damage; Ar- thur Antonelli discusses how to protect trees with non- toxic dormant oils; and, on the aesthetic side, Mary Rob- son choses bulbs for winter bloom.

Witch hazel lends its foliage colors and flower to this sea- son in Timothy Hohn’s article. Then Kelly Dodson assesses the flowering rhododendron species that bring color from now through March. And when you’re ready to purchase the plants you read about or are told to find by your land- scape designer, Valerie Easton explains how to locate them.

Late fall saw the passing of former editorial board mem- ber Kendall Gambrill, too early in his life. Ken was among the first to find sponsors for the color you see on these pages, and to lend his expertise on rhododendrons. A man of talent and humor, Ken Gambrill typified the spirit and generosity we are so fortunate to find in the Washington Park Arboretum.

Jan Silver, Editor

The Washington Park Arboretum Bulletin

Cover: a late winter bud of Rhododendron lanigerum — the promise of spring. This northeast Indian species blooms from February through March in the Pacific Northwest. Photo by Lynn Watts of The Greenery, specializing in species rhododendrons and new hybrids.

We dedicate this cover to the memory of Kendall Gambrill.

CONTENTS

2 . . Winter in the Washington Park Arboretum

by Jan Pirzio-Biroli

6 . . Rosemary Verey — the Gardener in Winter

by Steven R. Lorton

9 Small Bulbs for Winter Bloom

by Mary Robson

12 Understanding Winter Cold Damage

by Ray Maleike

15 .... Witch Hazel Winters by Timothy Hohn

21... Protecting Your Trees with Dormant Oils

by Arthur L. Antonelli

24 Flowering Rhododendron Species from

December through March by Kelly Dodson

27 In the Washington Park Arboretum:

Winter Damage by Timothy Hohn

29 For Further Information:

Where Can I Buy . . . ? by Valerie Easton

31 New on the Shelves of the

Elisabeth C. Miller Library by Valerie Easton

Book Review

32 The Gardens of Roberto Burle Marx

reviewed by Barbara Swift

In Bulletin articles, an asterisk (*) indicates species, in- cluding varieties and/or forms, that can be found in the Washington Park Arboretum; a dagger (f) indi- cates specimens in the public collections of the University of Washington 's Center for Urban Horti- culture.

The Washington Park Arboretum Bulletin is published quarterly, as a bonus of membership in The Arboretum Foundation. The Arboretum Foundation is a non-profit organization that was chartered to further the development of the Washington Park Arboretum, its projects and programs, by means of volunteer service and fund-raising projects. The Washington Park Arboretum is administered through cooperative efforts between the University of Washington, its Center for Urban Horticulture, and the City of Seattle Department of Parks and Recreation. The programs and plant collections are a responsibility of the Center for Urban Horticulture.

The mission of the Arboretum Foundation is to ensure stewardship for the Washington Park Arboretum, a Pacific Northwest treasure, and to provide horticultural leadership for the region. This stewardship requires effective leader- ship, stable funding, and broad public support. For membership information, write to The Arboretum Foundation, Uni- versity of Washington (XD-10), Seatde, WA 98195 or call (206) 325-4510. Articles on gardening and horticulturally related subjects are welcome. Please call for guidelines. For permission to reprint any part of the Arboretum Bulletin , please contact the Arboretum Foundation for written permission. © 1991 The Arboretum Foundation.

For information about the activities of The Arboretum Foundation, call (206) 325-4510. To receive information about public programs and lectures of the Center for Urban Horticulture, please call (206) 543-8800 or 545-8033.

Winter in the Washington Park Arboretum

Paulowina tomentosa.

by Jan Pirzio-Biroli

The Arboretum in winter is comparable to a garden at night. At night, I hear the small sounds that are suppressed in daytime by traffic, human voices, chain saws, washing machines — those many processes of daily life. In their absence, I hear, instead, the pervasive undertone produced by the multitude of creatures that are active after dark. Occasionally, the evocative rumble of a freight train sounds in the distance. Before dawn, the songs of wakening birds are a welcome concert.

Similarly, the Arboretum in winter offers views and vistas generally hidden by leaves for three

Glossary

Inflorescence is the flower cluster of a plant. Panicle is a branched flower cluster.

Pedicel is the stalk of a single flower. Tomentum is a downy-appearing cover com- posed of matted, woolly hairs that usually persist for the life of a rhododendron leaf.

Illustration by Kathleen Skeels

quarters of the year. The shapes of conifers stand out in an otherwise deciduous landscape. A grace- ful tree or a rather craggy one reveals its structure after the leaves have fallen. This effect is em- phasized when branches are outlined by snow. Unusually colored bark does not have the com- petition of spring bloom or autumn coloration. Textures of evergreen plantings chosen for their winter effect assume additional meaning. Flowers of winter-blooming species are more valued because they offer a display that is rare at this season. Following are a few examples chosen from hundreds of favorites.

The traditional subject for views in the Arbore- tum is Azalea Way, for which the traditional viewpoint is the Lookout (located west of the Ca- mellia Collection, below Arboretum Drive East). From there, one can see a portion of Azalea Way to the north until it disappears at a curve near midpoint. In winter, a more intimate scene opens from above the forested southwest corner of Woodland Garden, again looking north. The still- green swath of turf is bordered by conifers on the west. In the foreground, a small, graceful Japanese maple with copper bark frames the view; its warm tones are enhanced in early March when the young reddish leaves appear.

From the Lookout itself, the “flats” below emerge in winter. Trunks of birches whose bark varies from white to gray or occasionally pink, contrast with the yellow-green and purple masses

2

Washington Park Arboretum Bulletin

of red-osier dogwood stems. Toward the north- west, a superb specimen of our native grand fir {Abies grandis) stands alone against the sky, its narrow cone an imposing guardian near the boul- evard. Surprisingly, the east slope of Seattle’s Cap- itol Hill district presents an interesting combina- tion of vegetation and diverse architectural styles.

On sunny days, the island north of Duck Bay sparkles with the white trunks of European birches {Betula pendula ), and the wispy golden branches of native willows that have seeded in since the Arboretum was founded in 1934. They form an unbroken medley of color, a backdrop for the V-shaped ripples left by ducks swimming toward the shore in stately procession.

A much-loved group of conifers is the “ghost trees,’’ as they are called by some of the Arbore- tum guides when they introduce children to the pendulous forms of the Alaska yellow cedars {Chamaecyparis nootkatensis). These and other conifer species grow west of Azalea Way and south of the service road to the Lynn Street bridge. They are handsome on a clear day. When the mists come in, the distance between each is emphasized by layers of moisture, an effect that is present everywhere in the Arboretum on a foggy day.

The imposing pair of big-leaf maples {Acer macrophyllum) on Arboretum Drive East at the Brian O. Mulligan Sorbus Collection, have a sculptural effect, their major — nearly horizontal —

Above, branches of the Kentucky coffee tree {Gymnocladus dioicus ) with close-up of bark (below). Lower left, Stewartia monodelpha.

Vol. 54:4 Winter 1991/1992

3

branches sweeping southward and overlapping each other. In winter, their form is emphasized when continuous moisture has increased the layers of mosses on the bark, and the colonies of licorice fern ( Polypodium glycyrrhiza ) flourish after their period of summer dormancy. In con- trast, south of the Sorbus collection is a gaunt pair of Kentucky coffee trees ( Gymnocladus dioicus ) with coarse bark and awkward branches reaching toward the sky.

Japanese maples ( Acer palmatum) are well known for the variety of shape and color of their leaves. Apart from those attributes, in winter these deciduous cultivars excel in grace of form. They range from those with delicate, widespread- ing crowns, to dissected leaf forms whose multiple branches spread widely near the ground, assum- ing a contorted shape in maturity. Alternatively, the stripebark maples — A. davidii , A. rufinerve, and A tegmentosum, for example — often are sparse in outline. Their glaucous vertical mark- ings, however, seem to become more intense in winter, possibly the effect of moisture and cold, but also because the bare branches are more effec- tively revealed. The paperbark maple {Acer griseum) sheds satiny orange bark in curling plates and strips to reveal paler wood beneath. Although its autumn foliage is spectacular, this year-round tree suffers not at all when it stands without leaves in winter.

Stewartia monadelpha represents a combination

Licorice fem {Polypodium glycyrrhiza ) on western maple {Acer macrophyllum ) . Below, trunks of birches on Foster Island in the Washington Park Arboretum.

4

Washington Park Arboretum Bulletin

of graceful outline and handsome bark. The delicacy of its numerous slender branchlets is em- phasized, especially in the specimens with two or three trunks spreading from near the base. The finely shredding bark is a cinnamon color, fairly uniform throughout. A related species, S. pseudo- camellia, sheds its bark in plates to reveal a pat- tern and color reminiscent of more subtle ex- amples of camouflage cloth.

Line, color, and texture are combined in the empress tree ( Paulownia tomeniosa ) whose flower buds and fruits, borne in panicles, develop in late summer and remain together throughout winter on muscular, smooth gray branches. The capsules are ovate and woody, about Wi-2" long. The flower buds would be sufficient decoration, even without their promise of huge lavender flowers in spring. The 12" inflorescence is clothed in golden tomentum with small globose individual buds at the tips of numerous pedicels.

A recent planting north of the greenhouse uses varied evergreen species that offer year-round value for color and texture contrasts. These in- clude Eucalyptus , Podocarpus, palms ( Trachycar - pus fortunei ), and several grasses in varying forms and colors, contrasting with the voluptuous shin- ing leaves of Bergenia , blooming in pinks and rose during winter.

The Joseph A. Witt Winter Garden offers many contrasts, textures, forms, and colors, in ad- dition to a plethora of flower and fragrance. A single example is the bloom of cornelian cherry (i Cornus mas), which stands on the south slope. In February or early March, the haze of lemon- yellow flowers on branches devoid of leaves is especially beautiful when backlit by the winter sun. When its flowers have faded, an interesting repetition occurs somewhat to the east in the Woodland Garden where the male inflorescences of Lindera obtusiloba offer almost the same effect.

Like the small sounds of night, a walk through the Arboretum in this subtle season offers a multitude of surprises for us all.

Jan Pirzio-Biroli retired this year as naturalist for the Washington Park Arboretum and University of Wash- ington Center for Urban Horticulture. She is a former editor of the Washington Park Arboretum Bulletin , and recently started a new term as member of the Bulletin ’s editorial board.

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Rosemary Verey with the author’s son, Willie, in the Barnsley House garden.

Rosemary Verey— the Gardener in Winter

Photos and text by Steven R. Lorton

On the same page as Rosemary Verey’ s tele- phone number in my May 1985 travel journal, I ran into a quote I’d jotted down the day before my first visit with her, at her famous garden in Barnsley, northern England.

“A gardener must have a firm grasp of quality and form, and still be comfortable with the unruliness of nature. A gardener must see the big picture while focusing on every detail.”

I can’t remember where I heard it. That’s one of the engaging things about Britain. You hear so many wonderful things said about gardening, you

just don’t bother remembering who said what.

Anyway, I needed to talk to Rosemary about a story I was doing on her garden in winter to be timed with the 1988 release of her book, The Garden in Winter. I picked up the phone and dialed. It was early morning there; a cold, crystal- clear winter day on this side and matched, I was to find out, by the weather in the Cotswolds. The phone gave its funny little English hurraing twice and came off the hook. “Hello,” said a deep throaty morning voice that sounded more like Marlene Dietrich than an English country lady.

“Rosemary, it’s Steve in Seatde. How are your

“Lovely, thank you. I was just lying here looking out my bedroom window at the young red twigs of the lime trees. You call them linden . * Tilia. And I’m thinking, could anything be more beautiful?”

That’s how Rosemary is — paying attention, taking it in, responsive and communicative, of the moment. It’s little wonder that she’s turned out 12 excellent books on the art of gardening. Her

6

Washington Bark Arboretum Bulletin

* Laburnum way, I’d speculate, is the single most published garden image to come out of Britain. And she regularly jets across the Atlantic to lec- ture, judge shows, and design gardens.

She likes Americans, too! I asked her if she did

the first day I met her. “I do like Americans. There’s an open sweetness there that I find endearing.’

That melted my heart. The British strike me as so polished, so self-assured, so smooth and well turned out that whenever I'm there my mental

videos have me running around in rawhide and a coonskin cap.

We toured her garden. “When I find a plant I like and I can’t figure out where to use it,’’ she said, “I often ask myself where wouldn ’t this plant

work.’' We passed a bed of Polygonum bistort a ‘Superbum’. She said it was her idea of an excel- lent plant. I said I hated it. “I don’t know how a person could think that,” she said in gracious dis- belief. “They just look like weeds to me,’ ’ I said. She invited my family and me into the house for a lovely lunch, anyway. And so began an impor- tant friendship for me.

Forget the fact that Rosemary is a prolific gardener and writer, that she's spent much of her life in a huge seventeenth century house in the Cotswolds, that if some- one claimed she were the Queen's first cousin, you'd believe it. Rosemary Verey is a human being of enor- mous substance.

In February 1990, Duane Kelley had invited her over to judge and lec- ture at the Northwest Flower and Garden Show. Her agenda was packed, but Rosemary had corresponded with painter and plantsman Kevin Nicolay and she wanted to visit him.

Sadly, by that time, Kevin was in the last stages of AIDS. Rail thin, but dressed to the nines, even with a fancy hat cocked on his head to hide a sick and molting scalp, Kevin let us in and refresh- ments were served. Rosemary was bright and chatty, almost girlish in her demeanor. We talked of plants and gardening, laughed, and had a grand time.

Strong form and garden structure anchoring the unruliness of carefully selected plants is the substance of British gardening.

Vol. 54:4 Winter 1991/1992

7

Patterns are very important to Rosemary Verey.

Note stone paths, vegetable garden beds, garden chair, wall, and bare branches of deciduous trees— even ancient Barnsley House rising in the distance.

When Kevin became noticeably tired, Rose- mary said she was sorry but she really needed to go. There were cheerful hugs and good-byes. But when we got to the car, Rosemary was quite shaken.

For the rest of the trip, simple, understated references to the sadness of Kevin’s condition materialized repeatedly in her conversation. Shortly after the visit, Kevin died. But when Rosemary signed off her tenth book, The Ameri- can Man 's Garden , she remembered her Seattle visit and, I think, her own deep feelings. She dedicated the book to Kevin.

On the same trip, I remember her at Pike Place Market enthusiastically chewing a knockwurst from a fast-food restaurant and raving about the low price of salmon. She adored Seattle’s public market.

During dinner at my hosue one night she asked, “Was that a *Cornus ‘Eddie’s White Wonder’ I saw near the entry to your drive?’’ I said it was. “I thought so, I used one in Sir’s

garden.’’ My ears spread out and rotated in her direction like radar disks. Sir is Prince Charles! Rosemary works with him on his garden at High- grove. I knew I’d get the light touch if I asked her about the Prince then, so I just reached for the bottle of wine, a good Cabernet Sauvignon, filled up her glass, and waited.

An hour later I said brightly, “Does Prince Charles have a nice garden?” Rosemary perked up. I thought, Here it comes ! She talked about the garden, about trudging about in cold weather and working hard, about lunches alfresco, about the little princes — William and Harry — and how they stole her shoes once. But she never really said anything about the Prince. Rosemary is British.

I’ve never known her to go to any garden, or for that matter, any place , that she didn’t find something of value, something to get involved in or excited about. Once when she came into my of- fice downtown, one of the women had received a bouquet of roses that had flopped. Rosemary dis- appeared with them. We found her in the coffee room, sleeves rolled up, soaking the roses in hot water to revive them.

But my favorite memory of Rosemary Verey was made the first day I met her. She and my son Willie, who was five at the time, formed an in- stant bond. They strolled around the garden like two long-time chums. And after lunch, as we were leaving Barnsley House, she extended her hand to him for a shake. He was bashful and looked at the floor as he shook hands and said, “Good-bye.” “Now let’s do that again,” Rose- mary told him with a great, warm grin. ‘ ‘But you must look me in the eye. You must always look people in the eye.”

I love that memory. It’s so consistent with the Rosemary Verey I’ve grown to know. As in all things, she looks people and life in the eye. With Polygonum bistorta ‘Superbum’, with Kevin Nicolay, about the Prince, and with my son, she had a firm grasp of quality and form, yet was com- fortable with the unruliness of nature. She sees the big picture and still she focuses on every detail. She personifies that quote I jotted down. And that’s just the way she is. For, after all, Rosemary Verey is a gardener.

Steven R. Lorton, Northwest Editor of Sunset Magazine , is a board member of The Arboretum Foun- dation and liaison to the editorial board of The Wash- ington Park Arboretum Bulletin.

8

Waslhrigton Park Arboretum Bulletin

Small Bulbs for

Winter Bloom

Text by Mary Robson

Photos by Joy Spurr

T| efinitions of winter differ, but the common denominators in the Pacific Northwest may be sod- den ground, heavy skies, and ice skimmed across puddles. The inten- sity and duration of wdnter is un- predictable; its gloom for gardeners may be profound. But there is solace in winter bulbs, bright companions of early flowering shrubs. Solace

Crocus a?icyrensis (upper right) and C. chrysanthus ‘Advance’. Below, Crocus tomasinianus form.

Vol. 54:4 Winter 1991/1992

9

carries meaning beyond the commonly under- stood “comfort, assuage;” in seventeenth cen- tury usage it also connoted “delight, refresh, entertain." So it is in the spirit of their ability to delight and refresh our winter eyes that we wel- come the early blooming bulbs.

Seasons change subtly in the Pacific Northwest. The distinction between late fall and early winter is, at best, a gray blurred line. Fall-blooming species crocus sound the first notes of spring throughout November and into December; Crocus speciosus blooms in streaked bluish lavender. Late-blooming crocuses and fall cyclamen may persist into December in mild years. * Cyclamen hederifolium has delicate pink flowers with silver and green marbled leaves following flower; the evergreen leaves comple- ment later snowdrops and crocus. Crocus sativus , the saffron crocus, offers pale petals and vivid orange stamens. If you enjoy paella and want to plant saffron crocus in quantity, 4,000 individual flowers will yield one ounce of saffron.

Even as the garden borders lapse into sloppy dormancy, bulb leaves emerge. Crocus tufts like small green brushes, anemone’s lacy leaves, the floppy grape hyacinth foliage, and dabs of nar- cissus remind us of spring ahead. The first flowers venturing up may be snowdrops, often seen flow- ering before Christmas or on mild January days. The genus Galanthus, named for Greek “milk flower,” carries drooping bells of clearest white with chartreuse markings on the inner lip. Many hybrids of the common snowdrop, *G. nivalis , ex- ist, though differences between them, at least in photographs, seem minute — matters of plant height and leaf width. You may find G. elwesii , larger flowered and taller, or G. nivalis ‘Flore Pleno', double white. Why seek a double form when the clean, spare form of the common snowdrop satisfies as it does?

Snowdrops have been given many affectionate common names, among them ‘ ‘Fair maids of Feb- ruary” and ‘‘Candlemas bells,” as they bloom in England close to the Feast of Candlemas on February second.

The snowdrop in purest white arraie

First rears her head on Candlemas Day.

— Elizabeth Lawrence

Like all early winter blooming bulbs, snowdrops demand good drainage and prefer a woodsy, friable soil. They can take shade, especially shade under bare deciduous trees. Over-

collecting from the wild has been a consistent problem with Galanthus of all species; though cul- tivation in commercial settings is increasing, your best source is a friend willing to share a widening clump. Snowdrops, unlike most other bulbs, move well ‘‘in the green,” just after flowering and before leaves die. They prefer moist condi- tions while growing but can take summer dry. Since they transplant so readily in leaf, we gardeners can serve each other and the region by propagating and sharing snowdrops.

A fiercely brilliant yellow, the winter aconite ( * Eranthis sp.) is often pictured with snowdrops, both of them shaking off slushy snow. Garden writers encourage planting winter aconites in ‘‘sheets and drifts,” a prescription that is simpler to offer than to follow. The flowers are brass yellow, resemble buttercups (being also in the Ranunculus family), and are set off in bud and flower by a green frill resembling an Elizabethan ruff. Acquiring and establishing healthy bulbs may be difficult. Like snowdrops, Eranthis enjoy moving ‘‘in the green”; unlike snowdrops, they seem to dislike moving any other way. Fall- bought bulbs may be dead or dried out; soaking for 24 hours hydrates the bulb but won’t revive a dead embryo. In the Pacific Northwest, we may help our chances by recalling that Eranthis “is not fond of acid soils . . . below 5.5” (Bryan 1990). Perhaps we need to grow them on the edges of limed vegetable gardens. Elizabeth Lawrence wrote of fall-bought bulbs: “. . .they do not flourish like the ones that Mr. Krippendorf digs in great clumps from the spring woods and sends to me in bloom.” Alas, Mr. Krippendorf is gone, and we will have to rely on each other. Find that friend with the existing Eranthis !

Vernal crocuses are easier to locate and establish than either winter aconites or snow- drops; they increase reliably in Northwest soils. Think of crocus as needing sun, sun, sun — plant them where you and your cat like to bask on winter afternoons. Again, assure them of good drainage and good soil tilth. The delicate yellow Crocus ancyrensis blooms perhaps earliest. One hybrid is ‘Golden Bunch’; another early one is C. tomasinianus , floriferous when naturalized. Again a lover of lime, it “grows on woods and shady hillsides, especially on limestone” (Phillips and Rix 1989).

For most Pacific Northwest gardeners, the ac- cessible and dependable species crocus is Crocus

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Washington Park Arboretum Bulletin

chrysanthus and many of its cultivars. Blooming very early, with flowers larger than other species (but smaller than the late Dutch hybrids), these cultivars offer delight in pots or sunny garden cor- ners. Many were named by E.A. Bowles for birds: ‘Snow Bunting* is white opening to yellow sta- mens; ‘Bluebird* resembles one of its parents, C. biflorus , with pale lavender-blue flowers; and sev- eral are yellow feathered with brown on petal out- sides (‘Advance’, ‘Goldilocks’, ‘Gypsy Girl’, and ‘Zwaneberg Bronze'). Closed in rain to protect pollen, open in sun, crocuses tuck in neatly on rockeries, against the edges of walkways, in pots.

Iris — that immense, diverse family — offers winter-blooming bulbous iris, many fragrant.

* Iris danfordiae opens in early winter, a yellow miniature nearly flush with the surface of the ground, as if not wanting to stick its neck up into the cold. This 4" delight may not last long, as it is tasty to slugs and ‘ ‘ difficult to keep going in the open garden" (Phillips and Rix 1989). More long lasting and, perhaps, even lovelier is * I. reticulata with dark petals marked in yellow. Cultivars in- clude ‘Cantab’, ‘Harmony’, and ‘J.S. Pyk*. It combines nicely with Crocus chrysanthus ‘E.A. Bowles’, a clear yellow.

As the depths of winter recede, early Narcissus and Chionodoxa appear. Narcissus originated across Europe, and different species have different cultural requirements. One of the early dwarfs, N. cyclamineus , with petals blown straight back off the trumpet, appears to have been caught in a strong wind. Native to riverbanks, this one will thrive in a damper, shadier spot than many small bulbs. N. bulbocodium ‘Hoop Petticoat* swells from a tiny waist at the calyx to an open hoop, in soft yellow or creamy white. Late winter offers many narcissus hybrids — ‘February Gold’, ‘Feb- ruary Silver’, and ‘Tete a Tete' among the earli- est. ‘February Gold', a cultivar of N. cyclami- neus, has slightly swept-back petals, but its primary impact is the sturdy trumpet and hardi- ness. ‘Tete a Tete’, hybridized in 1949, opens two strong solid little flowers per stem. Dwarf nar- cissus, with the necessary good drainage, may be long-lasting in Northwest gardens, settling happi- ly into rockeries and shrub edges. All of these early bulbs can get mud splashed, rain spotted, or chewed up by early slug marauders. Plant them where some shelter is available, and increase your slug vigilance.

Many of these earliest flowers cheer winter

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with bright color, and either faint or pronounced fragrances. The winter garden is like the sparsely furnished teahouse with one flower at the altar: We stand in thin sunshine worshipping one snow- drop, tw'o narcissus. Winter slips away as imper- ceptibly as it came. The varied thrush song dis- appears, the snowdrops wilt, and tall narcissus and early tulips stride forward. We've been given, in winter, a meditative beauty to hold before we are overcome by the myriad voices of spring.

Mary Robson works for Washington State University/ King County Cooperative Extension as Master Garden- er Coordinator. She is on the boards of The Arboretum Foundation and the Bulletin .

Joy Spurr's photographs of plants can be seen in text- books and other publications around the world. She is a member of Unit 81 of The Arboretum Foundation.

References

Bryan, John. 1989. Bulbs (2 volumes). Portland: Timber Press.

Lawrence, Elizabeth. 1986. The Little Bulbs. Durham: Duke University Press.

Phillips, Roger, and Martin Rix. 1989. Bulbs. New York: Random House.

Vol. 54:4 Winter 1991/1992

11

Understanding Winter Cold Damage

by Ray Maleike

Plants in the Pacific Northwest may suffer winter injury from very cold temperatures or from other events related to winter weather. Win- ter injury can be caused by a complex combina- tion of occurrences, rather than a single factor, and the severity of injury may vary. If one under- stands how hardiness develops in plants, then action may be taken. It also may explain how a particular plant species may freeze out at +10° F in one locality and be perfectly hardy at 0° F in another place that is fairly close.

Predictions about the type and extent of damage are sometimes difficult to make in the Pacific Northwest because of the differing climates and microclimates. Temperature pat- terns will vary with change in altitude, being more moderate at lower elevations. Climate also is more moderate in close proximity to a large body of water such as Lake Washington or Puget Sound in western Washington.

Native plants within any geographical area have evolved into the environmental system of that area. These systems include extremes in hot/cold, wet/dry, sun/shade, summer/winter rains, pH, altitude, day length, and other factors. Over many centuries, weaker plants that do not tolerate the environmental extremes have disap- peared, leaving the stronger, more tolerant ones to reproduce. These plants are geared into the en- vironmental cues for their particular geographical area. Native plants in a given locale generally do not have problems with extremes — except for those one-in-a-hundred-year winters or those one- in-a-hundred-year droughts.

Exotic plants transplanted to a new area may not be able to adapt well to their new surround- ings if the conditions such as day length and other environmental phenomena are vastly different from their native area. Examples of problems stemming from the conflict between ecological range versus physiological range are the flowering dogwood ( *Cornus florida) and blackgum or tupelo ( *Nyssa sylvatica). Both of these plants have a natural geographical range from southern

New England to central Florida, and from the Atlantic Ocean west to eastern Texas and Oklahoma. Although each of these is the same genus and species throughout its range, many ecotypes exist. This means that the plants of either species from central Florida (27° N lat) are geared into different environmental conditions and cues than those from the Hudson Valley, New York (43° N lat). The plants from the southern end of the range will start to grow earlier in the spring, grow later into the fall, and be genetically less hardy in the winter. Either of these plants do well in western Washington but may suffer east of the Cascades if they are progeny of plants from the southern end of the range. Western Washington, with its limited native taxa, relies heavily on exotic plant materials for general landscape use, but sometimes reliance also leads to problems.

Hardiness

Hardiness develops in an organized, syn- chronous pattern. Shorter days — actually, longer nights — signal the plant that winter is coming. Physiological and hormonal changes within the plant start to prepare it for winter. The shortened days plus cooling temperatures cause the plant to become hardier with time. This is acclimation to cold or hardening. Without cooling fall tempera- tures, the acclimation process either does not oc- cur or proceeds very slowly.

The hardening process continues until the plant has reached its ultimate mid-winter hardi- ness, which is genetically controlled. The ulti- mate mid-winter hardiness of a Scotch pine ( *Pinus sylvestris ) from Finland is going to be greater than of one from the Pyrenees Mountains.

When temperatures start to warm up in late winter or early spring, the plant responds by de ac- climating or ^hardening. A series of warm days in February may cause plants to deacclimate or become less hardy rapidly. A sudden freeze at this point can damage a plant. When the plant begins to grow in the spring, the new growth usually will tolerate little, if any, frost without damage. As the spring progresses to summer and fall, the days start to get short and the hardiness cycle begins again.

Unusual Stresses

Every so often, abnormal weather or short-term climate conditions occur. These are those one-in- fifty, or one-in-a-hundred-year cold snaps, droughts, or rainy periods. Since 1981, depend- ing on the location in the Pacific Northwest, there

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Washington Park Arboretum Bulletin

Berberis darwinifs susceptibility to freeze damage can vary within a small geographic area.

have been three or four 100-year cold periods — at least it seems like it. All the freezes have done significant damage to plants and almost all have differed from each other.

Plant damage during cold periods such as De- cember 1990 may occur in a number of different ways. During a warm autumn, with little acclima- tion taking place, severe cold periods can damage many plants. This is what happened in November 1985. Many of the plants that were slow to ac- climate were killed to the ground, including species in such genera as 'Escallonia, *Cistus (rock roses), 'Rhaphiolepis, some 'Rhododen- dron, and other plants. Few native plants were in- jured. There is little that can be done in this situa- tion, except to cover the plants and hope to trap some heat from the soil.

Extreme cold happened in the third week of December 1983 (-9° F at Washington State

Glossary

Ecotype refers to a group of individuals of a species that are adapted to a particular environ- ment (Hitchcock and Cronquist 1973).

Taxa (singular, taxon) are ranks— such as genus, species, variety, etc. — in the formal sys- tem of scientific classification of flora or fauna.

University, Research and Extension Center, Puyallup where normal minimum temperature is + 10° F). Seattle and the Washington Park Ar- boretum stayed slightly warmer during that period. Plants that were killed to the ground in- cluded those mentioned above, some of the more tender * Pyracantha , and English or cherry laurel {'Primus laurocerasus). Little could have been done to protect these plants, although a cover may have helped.

The intense cold of February 1989 did a tre- mendous amount of damage in the generally milder parts of King County, Washington. The damage was caused by a warm period at the end of January, probably causing some deacclimation followed by the deep freeze beginning February 1 . Certain evergreens such as 'Berberis darwinii were killed to the ground in relatively mild Kent, Washington (+10° F) and were unscathed at a higher elevation in Auburn, Washington, at 0° F. Because the temperatures were generally colder at the Auburn location, the plants probably had not deacclimated as much as the Kent or Seattle plants had.

The freeze of December 1990 also was a period of intense cold following a warm autumn with no sufficient acclimating period leading up to cold weather. Damage to plants was very extensive. Plants that survived the February 1989 freeze in King County were severely injured or killed in

Vol. 54:4 Winter 1991/1992

13

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December 1990. With both of these freezes, there was little that could have been done.

Another type of damage associated with the cold is sun scald to leaves and stems or trunks. Any intense cold period in the Pacific Northwest is almost always accompanied by bright sunshine. The sun can heat evergreen leaves and bark well above the daytime ambient air temperature, which on clear days is usually well below freezing. When the sun goes down, the tissue in the leaves freezes rapidly, causing ice crystals to form, punc- turing and killing leaf or stem tissues. The plant damage is caused on the south and southwest parts of the plant. This winter injury may be diminished by shading the plant during the sunlit hours. Consider wrapping trunks of thin-barked trees with a light-colored material for at least one growing season.

Roots are usually never as hardy as the above- ground plant parts. Stems of saucer magnolia (* Magnolia soulangiana ) can, with proper ac- climation, tolerate temperatures of -25 to -30° F, but their young roots may be killed at 24 to 25° F. * Cotoneasters, some * dogwoods, and * hollies also have relatively tender roots. Plants in the

ground generally do not have many problems be- cause soil retains a certain amount of heat. How- ever, the temperature of plant roots in a con- tainer— out of the ground — may approach air temperature. This could easily kill the roots of all but the most hardy plants. When plant roots die from freezing, but the top does not, the plant may begin to leaf out in the spring and then die for no apparent reason. To avoid freezing of roots, bring the containerized plant into a cool but moderated temperature, such as a garage, or bury the pot in the ground with a good mulch over the root sys- tem. If the plant is kept inside, the plants might still need a certain amount of chill to break dor- mancy so they can grow again in the spring.

Late spring frost might also injure plants that have a tendency to flush early in the spring. Plants in this category are early blooming rhododendron cultivars such as *‘PJM’ and * ‘Christmas Cheer’, Higan cherries ( *Prunus subhirtella cvs), Fraser’s photinia (fPhotinia x fraseri), and others. This type of problem may sometimes be avoided by covering the plant, or allowing a sprinkler to sprinkle the plant all night long. If the plant is to be sprinkled, the air temperature should not be below 27° F, and the sprinkler should be left on until the air temperature is well above freezing. Sprinkling new growth during light frosts is commonly done in commercial apple orchards.

If a particular plant seems to receive winter damage regularly, it may be wise to replace it with a hardier cultivar or devise some system to put the plant in a moderated climate each winter.

Plants develop hardiness in accordance with the genetic background and the developing weather patterns for a particular season. We can help them by making sure they get into the winter season in the healthiest state possible. This means to make sure they are under good nutrition, not starved or over fertilized; under good water relations, not drought stressed; and without any serious disease or insect stresses. Healthier plants are hardier.

Dr. Ray Maleike is extension horticulturist with Washington State University, Puyallup.

References

Dirr, Michael A. 1990. Manual of Woody Landscape Plants. Champaign, IL: Stipes.

Hitchcock, C. Leo, and Arthur Cronquist. 1973. Flora of the Pacific Northwest. Seattle and London: University of Washington Press.

14

Washington Park Arboretum Bulletin

Witch Hazel Winters

by Timothy Hohn

On a crisp fall day in 1975 I traced my way through the wolverine woodlands of Metro- politan State Park, just outside Detroit, with my requisite pint of cider and greasy bag of fresh baked doughnuts. I was scouting for a pristine, secluded picnic spot.

On a moist woodland bank, covered with a tinted collage of fallen red maple, hickory, and oak leaves, my nose was piqued with the subtle aroma of sweetly scented soap. At first I saw no possible source for such a fragrance — understandable, it being fall and no flowers to be seen. My suspi- cions were drawn to a rather neat thicket of multiple-stemmed, large shrubs with golden foliage. Upon closer inspection, the fragrance became more intense and — Aha! — peeking out beneath the cloak of glowing leaves were some very bizarre looking flowers , of all things! I marveled at the seasonal paradox of the yellow, whimsical flowers of the eastern witch hazel, Hamamelis virginiana. The cider was especially sweet that day.

Since that cider-fueled discovery nearly two decades ago, witch hazels have had a fixed place on my list of favorite, temperate garden plants. The phenological paradox among eastern witch hazels of autumn flowers with ripening fruit is ex- pressed in the generic name given to these plants: Hama (together with) and metis (the apple). I have yet to try divining for water with its twigs, but the common name witch hazel belies a utility to this task. Little did I know at the time of my autumn discovery that our native eastern witch hazel is perhaps the most benign garden plant of the genus. Learning later that they are also members of a fascinating parallel flora of glacial refugees distributed in eastern North America and east Asia only added botanical admiration to an already burgeoning horticultural interest.

Pacing carefully around that golden wood of Michigan witch hazels long ago, I rewarded myself time and again with a closer gaze at the dainty, arachnoid flowers and the clear yellow foliage concealing them. Unbeknownst to me, and with a slight leap forward two to three months in

the calendar year, this scene could easily have been repeated in the hill country of Japan or cen- tral China — perhaps without the cider and dough- nuts! Witch hazels are clanishly consistent about their living quarters. So although the Asian and American species are found widely separated, their woodland habitats are remarkably similar.

Unfortunately, for a rather small genus, there remains some uncertainty about whether it con- sists of five species or only four. For simplicity’s sake, and due to the fact that the questionable fifth species is exceedingly uncommon, let’s consider the four species that we’re sure about: They are 'Hamamelis virginiana, *H. vernalis , *H. mollis , and *H. japonica. Many authorities consider the questionable fifth species, *H. macrophylla , to be a southern form of H. virginiana. In those cultivated settings where H. japonica and H. mollis are grown together, they hybridize with some spectacular results. The progeny of this hybridization are included under the name H. x intermedia with selected clones being registered under specific cultivar names. These selected hybrids are particularly good garden plants and I shall review them later.

As a small group, it’s easy to generalize about witch hazels. For one thing, they are all perfectly hardy garden plants in the Puget Sound region, with representatives from all species in the Washington Park Arboretum. I tend to categorize them as small, multiple-trunked trees, although H. vernalis and some of its selections scarcely rise above the stature of shrubs. Their vase shape is very reminiscent of hazelnuts, as are their or- bicular, asymmetrical deciduous leaves. On the whole, however, this is an insulting comparison, since the genus Hamamelis is far more refined in character and ornament than hazelnut (fCorylus spp.). For the avid nut gobbler, however, the superlatives can be reversed because the woody, two-valved capsule and hard seed of witch hazel makes a poor snack.

Perhaps the singular most interesting feature of

Glossary (after Webster’s)

Petiole is a leaf stalk.

Phenology, here, refers to the branch of science dealing with the relations between climate and periodic biological phenomena such as plant flowering.

Vol. 54:4 Winter 1991/1992

15

s

Hamamelis x intermedia ‘Hiltingburg’ in October.

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Hamamelis x intermedia ‘Winter Beauty’ in January.

Washington Park Arboretum Bulletin

Hamamelis x intermedia ‘Diane’.

Dcmd McDonald

all the witch hazels is their habit of flowering dur- ing the cold season. I’m not referring to minute, lifeless little specks only a botanist or curio gar- dener could love. These are real flowers with bright colors, fragrances, and everything — often in the middle of winter! Flowering times range from mid to late fall for Hamamelis virginiana , and through the winter to March for some hybrid cultivars. The flowers vary in size but they all have the appearance of dainty shreds of papier mache, the limp petals often cast out from the bud in a crinkled and twisted trajectory. They occa- sionally remind me, clustered along the branches this way and that, of a colorful phalanx of spiders about to descend by their silken threads. Shades of yellow are the predominant colors among the species; the hybrids strike off into the orange and maroon portions of the spectrum.

Witch-hazel leaves are always attached in alter- nating positions along the branches and have uneven bases where their petioles connect — sim- ilar to elm. Although the shapes of their leaves may vary slightly from widest at the base to widest toward the tip, they always have distinctive parallel veins. The leaves of the Chinese species, H. mollis , are quite fuzzy and appear soft and flannel-like. Though touted for their interesting flowers, their fall color provides stiff ornamental

competition. Like the flowers, shades of yellow are common and appealing, but some fire up the gar- den with gold, tangerine, and maroon — some- times on the same leaf!

Hamamelis virginiana

The eastern witch hazel, Hamamelis virgini- ana, with its uniquely aromatic bark, is a common member of the woodland understory from New England to Michigan and south to the Gulf Coast states. Like most of its brethren, this witch hazel is communal and can usually be found in small groups, colonies, or thickets with their roots firm- ly anchored in a moist, well-drained organic soil. They share space in New York with Acer pensyl- vanicum and Kalmia latifolia , in Michigan with Ostrya virginiana and Carpinus caroliniana , and are neatly nestled into the Georgia foothills with Rhododendron minus and Oxydendrum arboreum.

Sometimes reaching 25 to 30' tall and as much wide, H. virginiana is the largest of the clan. Un- fortunately, it is perhaps the most pedestrian in ornamental value, particularly because the yellow fall foliage hangs on to conceal the mid-to-late autumn yellow flowers. The faint perfume of the flowers, however, thankfully penetrates the leafy curtain. I have seen references to a clone of this species which is purported to drop its leaves early,

Vol. 54:4 Winter 1991/1992

17

exposing the blooms. There is also mention of a variety, henryae , said to have small, silvery leaves and strongly fragrant flowers.

Hamamelis vemalis

Our smaller native cousin of the eastern witch hazel is Hamamelis vemalis , the vernal witch hazel of the Ozarks. Growing in suckering thickets along creek bottoms, this midwinter bloomer is often only 6 to 10' tall and rarely suckers in cultivation in the Northwest. Open grown plants can become quite wide, often twice their height. The foliage of vernal witch hazel turns a crisp, clear yellow in the fall before drop- ping. The flowers, like the plant, are the smallest of the group with petals sometimes only 4 to 5 mm long. However, what it lacks in size it makes up for in quantity, hardiness, and color. Flower petals unfurl in January or February in shades from light yellow, orange, copper, and red from flower buds that thickly stud the branches. This warm haze of color is punctuated by a pleasant yet indescribable aroma. It is a popular plant in colder climes than ours, its flower petals curling up in a warm huddle on cold days and rolling out un- scathed under balmier conditions. Though this species is another somewhat disappointing native, there are some very interesting selections — not surprising since there is quite a bit of natural variation within H. vemalis. My favorite, and one of the more interesting witch hazels for the garden, is Hamamelis vemalis ‘Purpurea’. The flowers are small but plentiful and of the most unusual color — a sort of Peruvian violet, unlike any others. Unfortunately, I also must report the tenuous nature of this name since I have not yet been able to uncover its origins. The cultivar ‘Sandra’ was selected at Hillier’s nursery in England in 1962 for its plum-purple new growth and collage of fall foliage colors in orange, scarlet, and red. The cultivar ‘Lombart’s Weeping’ is a flat-to-pendulous selection of dubious distinction, since this form is said to occur naturally in the wild. Nevertheless, the form is handsome, par- ticularly when fully clothed with leaves.

Hamamelis mollis

For my money, the Chinese witch hazel, Hamamelis mollis , is the most ornamental of the naturally occurring taxa and a very good land- scape selection overall. It has cornered the market in yellow: yellow fall foliage and yellow flower col- or. The leaves and flowers are the largest of the genus, although in stature the Chinese witch

hazel is usually second to our native easterner. Adult plants in the Joseph A. Witt Winter Garden are 20' tall with a gracefully arching, vase shape.

Hamamelis mollis grows in the hillside wood- lands of east and west central China as high as 7,000 feet. Ernest Wilson describes it as the com- monest of woodland shrubs in western Hupeh Province where it flowers in late March and early April, two to three months behind its cultivated brethren in the Arboretum. When they are out, the flowers can be as large as half dollars with stout, strappy petals and a deliciously powerful scent. Blooms often appear around the first of the year and may last for six weeks, depending on the weather. More than once, my January hopes for spring have been revived with the unmistakable, but indescribable, scent of the Chinese witch hazels in the air — sometimes discernable 100 yards away. There is little to improve upon with the Chinese witch hazel, thus the few good selec- tions that exist barely guild the lily. The most popular clone in Europe and the British Isles is ‘Pallida’, said to be more thickly flowered, richer of color — a golden yellow — and hardier than the species. Although I don’t believe there is any room to improve upon the scent of H. mollis , ‘Pallida’ is equal to it.

Hamamelis japonica

The Japanese witch hazel, Hamamelis japon- ica, is definitely the “poor relative’’ compared with the more ornamental Chinese species. However, it lends an important genetic compo- nent to the various hybrid progeny it produces with H. mollis. The Japanese witch hazel is cer- tainly the more slender of the two large Asian species. Its leaves are smaller than that of its Chinese counterpart, with longer petioles and a smooth surface. The flowers of Japanese witch hazel are always later than those ofH. mollis , ap- pearing in late January and February, and are composed of thinner, crinkled petals. The flowers don’t reach the half-dollar size of Chinese witch hazel, but the crinkling does give them a distinct character and unusual aspect. They are always some shade of yellow with a carmine center. Perhaps the most attractive of this species is its variety Hamamelis japonica var. flavopur- purascens, which often has a pleasantly mottled fall color in shades of yellow, bronze, and red. The flowers are yellow suffused with carmine which intensifies toward the base of each petal. Hamamelis x intermedia

The cultivated hybrids between the Chinese

18

Washington Park Arboretum Bulletin

and Japanese witch hazels offer a wide variety of delightful garden characteristics — some are the perfect synergy between the two species. These hybrids arose independent of each other at the Ar- nold Arboretum, Jamaica Plain, Massachusetts; the Botanic Garden in Charlottenlund, Denmark; in the nurseries of Heinrich Bruns in Germany; and especially at the Arboretum Kalmthout, Belgium. The flowers are often quite revealing as to the specific influence of each parent. Of the 1 5 to 20 named hybrid selections, the flowrers can vary in bloom time, size, color, texture, and scent. By “flower texture’ * I am referring to those visual characteristics determined by petal number per flower and petal thickness, as well as the smooth or crinkled nature of the petals. None of the hybrids is any more fragrant than Hamamelis mollis , but they certainly do broaden the color range available.

With these hybrids, the flower colors available within the genus Hamamelis cover the hot por- tion of the spectrum from soft, warming yellows to simmering maroons. The same can happily be said for the cheerful and fiery display of fall foliage colors. With careful selection, it’s possible to have a bright display of colors from summer to fall and on through to spring.

A good combination of witch hazels for a long season of wdnter bloom (60 to 90 days) would be the hybrid cultivars "“Arnold Promise’, * ‘Diane’, "“Jelena’, * ‘Winter Beauty’; Hama- melis mollis and *H. vernalis ‘Purpurea’. The hybrid cultivar ‘Winter Beauty’ would be the first to bloom, sometime close to Christmas, with its yellow-orange flowers and tremendous fragrance. Although its flowrers are small, their abundance makes them very noticeable. Close on its heels wrould come H. mollis , and ‘ Jelena’ with its cop- pery flowers. One must be patient writh ‘Jelena’ as it is shy about dropping its leaves, which can be intrusive at bloom time. Older plants should over- come this youthful tendency. I include 'Jelena' here mainly because it extends the bloom season in the orange color range initiated by ‘Winter Beauty’. ‘Diane’ comes next and it is currently the best of the red- or maroon-colored selections with outstanding deep red-to-maroon fall color, as well. The cultivar ‘Arnold Promise’ and H. ver- nalis ‘Purpurea’ come last in February and make a striking color combination in light yellow7 and violet. Keep in mind that the blooming period and timing will vary, depending on the prevailing

weather conditions. This combination of plants will provide a long and overlapping bloom period with the greatest intensity probably occurring in January. For recommendations of some of the more useful species, species cultivars, and hybrid cultivars, see the shaded list (page 20) accom- panying this article.

Cultivation

Witch hazels are best planted in a well-drained, moisture-retentive soil in partial shade, in keeping w7ith the conditions under which they are found in the wild. However, in the Pacific Northwest they will tolerate full sun if they are provided with sup- plemental irrigation. When siting new plants, consider locations with dark, coniferous back- grounds for suitable contrast with the delicate flow7ers. As an alternative, place witch hazels w7here soft winter rays will backlight the translu- cent petals, thereby magnifying their intensity. This wrorks particularly well with the darker color forms that appear paler in shade or flat light. Don’t forget to position the fragrant selections close to pathways or in the path of gentle breezes headed toward unsuspecting noses. Witch hazels also are good overstory companions for rhododen- drons and their relatives, mixed with winter bulbs. They are generally free of pests and diseases in the Pacific Northwest and, if sited cor- rectly, require little on-going maintenance. One cautionary note: the hybrid cultivars are often grafted and one should be diligent about removing any understock suckers that may appear.

Witch hazels are versatile landscape plants suitable as specimens for the small backyard or in striking masses for commercial or institutional grounds. One plant of Chinese witch hazel can brighten the dreariest of winter yards. On a larger scale, imagine a planting of four dark green Nord- mann firs (* Abies nordmanniana), fronted with a half dozen witch-hazel selections perfuming the atmosphere and representing the full range of seasonal colors in yellow, copper, and maroon.

Timothy C. Hohn is Curator of Living Collections, Washington Park Arboretum and University of Wash- ington Center for Urban Horticulture.

Reference

Wilson, E.H., and Charles S. Sargent, editors. 1988. Plantae Wilsonianae . Publications of the Arnold Ar- boretum, no. 4: Biosystematics Floristic and Phylogeny Series, volume 3. Volume 1, pp 43T432. Portland: Dioscorides Press.

Vol. 54:4 Winter 1991/1992

19

Witch Hazel Recommendations and Viewing Locations

The following are recommended selections of witch hazel based on the performance of a limited number and range of plants at the Washington Park Arboretum and the Bos- koop Experimental Station, The Nether- lands. Obtain a map of collections at the Graham Visitors Center. Request propaga- tions at the nearby Pat Calvert Greenhouse, 10-12, Tuesdays.

H. x intermedia cultivars

Arnold Promise’: flowers are large, light yellow, and fragrant in late February; fall color mottled yellow, orange, red. (Hama- melis Collection).

‘Barmstedt Gold': flowers very large, deep golden yellow, and with a slight fragrance in early February.

* ‘Diane’: flowers are medium, carmine red in January to February; fall color crimson. (Winter Garden and Hamamelis Collection). *‘Jelena': flowers are large, coppery orange in early January, extending the orange color season begun with ‘Winter Beauty’. (Winter Garden).

* ‘Primavera’: flowers large, canary yellow in January and February. (Hamamelis Collec- tion).

‘Westerstedt’: flowers are large, canary yellow in late February, slight fragrance.

* ‘Winter Beauty’: flowers are small, abun- dant, yellow-orange in December to January; very fragrant. (Winter Garden).

Hamamelis mollis

*H. mollis : flowers are large, golden yellow, very fragrant in early January; fall color yellow. (Winter Garden and Hamamelis Col- lection).

*H. mollis ‘Pallida’: flowers are large, light yellow, very fragrant in January; fall color yellow. (Winter Garden).

Hamamelis vemalis

*H. vemalis ‘Purpurea’: flowers are medium to small, striking violet color. (Hamamelis Collection).

H. vemalis ‘Sandra’: foliage color plant has outstanding, mottled autumn colors of yellow, orange, and scarlet; new spring growth is tinged purple.

20

Washington Park Arboretum Bulletin

Protecting Your Trees with Dormant Oils

by Arthur L. Antonelli

This often overboked alternative to conventicmal pesticides is used to control some Pacific Northwest pests.

Jt is a time of rising concern about ways in which conventional pesticides adversely affect organisms surrounding their target plants, as well as ecosystems in general. Consultants, land- scapers, and gardeners must look for and concen- trate on the effective use of bio-benign alter- natives, limited though they may be.

We can identify only a fewr examples of such alternatives for pest control. These include: for- mulations containing insecticidal bacteria (e.g.. Bacillus thuringiensis), soap insecticides, abrasives, borates, growrth regulators, botanicals. and high-grade horticultural oils.

As an alternative pesticide, the horticultural oils seem to be continuously overlooked, possibly because of the fear that they might injure plant leaves (phytotoxicity). This fear may have been warranted in past decades, but modem spray oils have come a long way in refinement (Capizzi et al. 1982). As a testimonial to renewed interest in oils, one only has to go to the scientific literature and observe many of the recent reviews or ex- perimental wrork involving oils and landscape plants (Capizzi et al. 1982; Johnson 1985; Baxendale and Johnson 1988 a. b; Miller 1989; Grossman 1990). Oils today are far safer to plants than were their progenitors. Indeed, with some care in choice of material and application, many plants can be sprayed during the dormant or delayed dormant period with no concern for harm to the plant. In many cases, this also includes oils applied in the summer.

How Safe are Spray Oils?

Used according to label instructions, horticul- tural oil poses no threat to human beings or pets. Short of taking a bath in them or swallowing copious amounts, oils are among the safest of pes- ticides.

The real question is how safe horticultural oils are to plants. There are twTo wTays of answering

Cottony camellia scale on yew. This species attacks holly as well as camellia and yew.

this question. First, authorities (Baxendale and Johnson 1988a; Miller 1989) document re- sponses of specific plants for both dormant and summer oils. Warren T. Johnson, a leader in the field of horticultural oil research, has not found any published work demonstrating phytotoxicity to any species of deciduous tree or shrub in the United States from the use of high-grade horticul- tural oil applied during the dormant stage (Johnson 1980). Indeed, I've found that the same is true for many conifers. However, there are indi- cations that oils are sometimes phytotoxic to some junipers. Also, the classic response of Colorado blue spruce to oils is the loss of its bluish hue following application.

The second way to deal with the question of safety is to simply abide by the label itself. Use the

Glossary

w

Bio-benign indicates an action or substance not harmful to plants or non-target animals.

Borates are a salt or ester of boric acid.

Dormancy is a period of inactivity in plants.

Delayed dormancy is the period just before physiological activity7 begins in plants.

Overwintering is the stage and condition in which insects spend the winter.

Phvtotoxicity is the eliciting of a toxic reac- tion in plants. The condition occurs when foreign materials (e.g., chemicals) cause an adverse reaction such as burning, stunting, etc.

Vol. 54:4 Winter 1991/1992

21

Don Normark

oil only on the plants listed and pay special atten- tion to lists indicating certain plants to which it is toxic. Mix according to instructions. Also, avoid applying dormant or delayed dormant oils in temperatures below 40° F or when temperatures might approach freezing soon after application; this may cause injury to the plant. The label can determine the specifications for superior oils.

Unfortunately, no horticultural oil label pro- vides a total picture of what is actually in the con- tainer. Theoretically, some indication of un- sulfonated residue (UR), gravity, viscosity, distilla- tion range, and pour point should be on the label. At the very least, the UR rating must appear on the label that is intended for use. The UR (un- sulfonated residue) rating is an index of the amount of the product free from unsaturated hydrocarbons. Injury to plant leaves is related to the percentage of unsaturated hydrocarbons in an oil. An oil with a UR of 92 percent or more is considered safe on green plant leaves (Capizzi et al. 1982).

According to Warren Johnson (1980), factors that cause phytotoxicity are:

1. overdose;

2. wrong timing of spray

a. don’t spray when buds have fully opened and shoot elongation is occurring.

b. don’t spray when there is an obvious moisture deficit observed in leaves.

c. don’t spray sensitive plants when the relative humidity is expected to remain over 90

percent for a period of 48 hours;

3. mistaken dormancy (fall); and

4. genetic variability.

Writes Johnson: “Should phytotoxicity occur, the user failed to account for one or more of these factors. The extent to which genetic variability oc- curs is not known.’’

Another question is about the impact of oil sprays on beneficial insects. Oils are not selective as to what eggs or other life forms they kill. For example, the valuable eggs of overwintering pred- ators also can be killed while applying oil to the eggs of pest species. The “up side’ ’ of this is that oils are short-term-contact insecticides that kill only organisms immediately covered by the oils (Grossman 1990). Any subsequent movement of beneficial organisms into the area is not affected and survival is assured.

How Dormant Oil Kills Pests

Researchers believe that oils prevent or impair pest survival in three ways (Willett and Westigard 1988). First, oils interfere with the ability of the pest to obtain oxygen by plugging air-exchange apparatuses, causing suffocation of insect and mite eggs. It is important to note that eggs are more vulnerable when winter is ending and hatching is near. This reflects many consultants’ recommen- dations that applications during delayed dormancy are more effective against eggs than are dormant applications, since the former method more close- ly coincides with the end of overwintering. A sec- ond way in which oils kill pests may be the pene-

Rosy apple aphids on underside of apple leaf. Note the curling distortion. This is caused by toxins associated with feeding when aphids insert their mouth parts. A healthy Malus ‘ButterbalT (left), with orange-yellow fruit.

4

m

Arthur L. Antonelli

tration of the pests’ cuticle and subsequent inter- ference with nerve transmission. The authors in- dicate that there are no data, however, to support this speculation. Third, oils act as repellants to pests as well as killing them outright.

Common Target Pests Susceptible to Oils

In ornamental landscapes in the Pacific North- west, some of the pests most vulnerable to oil ap- plications during delayed dormancy include a number of aphid species that overwinter on the targeted host as exposed eggs and several scale species that overwinter on targeted hosts in the very vulnerable nymphal stage. Apple aphid {Aphis pomi ) and rosy apple aphid {Dysaphis plan- taginea) are two common aphid pests of apple and flowering crab apple (* Malus spp.). The apple aphid causes wilt in growing tips and can stunt growth, whereas the rosy apple aphid causes ex- treme leaf distortion that can extend to fruit dis- tortion and stunting, as well. Both overwinter as eggs on twigs and spurs of their hosts. Leaf-curl plum aphid {Anuraphis helichrysi ) and black cherry aphid {Myzus cerasi ) cause severe distor- tion to the leaves of flowering plum and flowering cherry {Prunus spp.). Additionally, their excre- tions lead to the build-up of unsightly sooty mold. These aphids also overwinter as eggs on the tar- geted host and as such are vulnerable to delayed dormant oil. Two common scales that overwinter on their hosts as vulnerable nymphs are the Le- canium scale {Lecanium spp.) and the brown soft scale (( Coccus hesperidum ). The Lecanium scale has hundreds of host plants ranging from blue- berry (* Vaccinium corymbosum), to many of the flowering * Prunus species. The brown soft scale also has many hosts that include dogwood {*Cor- nus spp.) and many other favorite landscape plants.

Additional species that overwinter on known hosts as vulnerable nymphs include: San Jose scale {Quadraspidiotus perniciousus ), cottony camellia scale {Pulvinaria floccifera ), azalea bark scale {Eriococcus azalea ), and cottony maple scale {Pulvinaria innumerabilis).

Without a doubt, a properly applied delayed dormant oil spray will do a good job of controlling most overwintering populations of these scale or aphid pest species. However, you are limited by the legality of the product, so read the labels on the containers. Even with this limitation, delayed dormant oils are a useful alternative to conven- tional pesticides when they can be used legally and effectively. Additionally, as more and more

Pruning with Design

641-5220

research in our area reveals safe and effective con- trol of certain summer stages of pests, we will see more recommendations for use of oil in summer by professional plant care consultants.

References

Baxendale, R.W., and W.T. Johnson. 1988a. “An Evaluation of Dormant Oil Phytotoxicity on Six Species of Woody Ornamentals.” Journal of Arboriculture 14(4): 102-104.

Baxendale, R.W., and W.T. Johnson. 1988b. “Eval- uation of Summer Oil Spray on Amenity Plants.” Journal of Arboriculture 14(9): 220-225.

Capizzi, Joe, PH. Westigard, and Jim Witt. 1982. “One of Our Under-utilized Insecticides — Horticul- tural Spray Oils.” Ornamentals Northwest Newsletter. January-February-March 1982: 17-19.

Grossman, Joel. 1990. “Horticultural Oils: New Summer Uses on Ornamental Plant Pests.” IPM Prac- titioner. XII (8): 1-10.

Johnson, Warren T. 1980. “Spray Oils as Insec- ticides.” Journal of Arboriculture 6(7): 169-174.

Johnson, Warren T. 1985. “Horticultural Oils.” Journal of Environmental Horticulture 3(4): 188-191.

Miller, F.D. 1989. “The Use of Horticultural Oils and Insecticidal Soaps for Control of Insect Pests of Amenity Plants.” Journal of Arboriculture 15(11): 257-262.

Willett, M., and P.H. Westigard. 1988. “Using Horticultural Spray Oils to Control Orchard Pests.” Publication PNW 328. 8 pages.

More Reading

Cox, Peter. 1985. The Smaller Rhododendrons. Portland: Timber Press.

Cox, Peter. 1990. The Larger Rhododendron Species. Portland: Timber Press.

Davidian, H.H. 1982. Rhododendron Species. Vol- ume I: Lepidotes. Portland: Timber Press.

Davidian, H.H. 1989- Rhododendron Species. Vol- ume II: Elepidotes. Portland: Timber Press.

26

Washington Park Arboretum Bulletin

In the Washington

Park Arboretum! Winter Damage by Timothy Hohn

he few redeeming aspects of our recent spate of cold periods are the tremendous shows of bloom by those plants, such as Syringa and Malus , normally dissatisfied with our mild Puget Sound winters. Also, and more importantly for the Arboretum, is the opportunity to evaluate the hardiness of plants in the face of stressful weather conditions. Let me assure you, however, that this academic attitude is often poor recom- pense for the disappointing losses we experience during these periods, which we always hope are the last ones.

What makes the severe cold so devasting is that it is not usually preceded by progressively colder periods, such as light frosts followed by hard freezes, which contribute to the acclimation or “hardening off” of plants. Consequently, many of our ornamental plants are “soft” and vulner- able to freezing injury. Plants that would survive such cold spells unscathed in the easterm United States, where they are adequately preconditioned by hot summers and progressively cooler autumn weather, are severely damaged in the Puget Sound region. This phenomenon is unaccounted for in hardiness zone maps and unpredictable for those who rely on them without question.

Before our December 1990 freeze, we experi- enced nearly balmy conditions at the Arboretum with more than usual moisture, two light frosts, and daytime highs in the 40s and low 50s. Then the express came to town. On December 17, 1990, we had a high of 52° F and a low of 43° F; 24 hours later the mercury stood at 25° F and dropping. Ten inches of heavy, moisture-laden new snow and a bone-chilling 5 0 F still seemed a fitting first day of winter on December 21. As is often the case during cold spells, the sun shone brightly on limp and curled foliage, too weak to warm the air but adequate to desiccate exposed plants. To add injury to injury — and after a very brief thawing, sufficient to melt the insulating blanket of snow — the mercury was at 10° F for two successive nights, with bright sunshine dur- ing the intervening days to complete the scorch- ing begun earlier.

The final outcome of this miserable weather is still being fully assessed at the Arboretum. In fact,

we may not see the final results of the impact on certain plants (e.g., some trees), for another year or more. Cold-stressed plants with no immediate- ly observable signs of cold damage may neverthe- less be rendered highly susceptible to secondary pathogens and otherwise benign insect popula- tions. It’s amazing to me how long some plants with severe cambial damage can survive on sec- ondary reserves and reduced water uptake until the hot, dry weather hits. It was not uncommon to see plants that looked completely unscathed, such as shrubby species of Arctostaphylos , col- lapse during warm days.

The most severe damage in the Arboretum was sustained by trees that were broken up by exces- sive snow loads during high winds. Many trees were toppled over by heavy snows, high winds, and spongy or shallow soil conditions. Of the small but diverse collection of southern beeches ( Notbofagus species), we lost four different species to breakage and wind- throw. The total estimated value of the loss to the Arboretum in tree damage is S 260,000. Fortunately, because we collect and grow more than one of any species or cultivar, total losses were actually few.

Freeze Damage

The most striking results from the storm are the effects on broadleaved evergreens in various types of exposures. For instance, Maytenus boaria , a fine-textured small tree from Chile, was frozen to the ground in exposed sites but only slightly defoliated in the shade of larger trees. This phenomenon, caused by physiologic drought, can be observed throughout the Arbore- tum among several different genera of broadleaved evergreens. A standard precaution against this sort of damage in areas that regularly experience cold, sunny winters is to confine broadleaved evergreens to areas with winter shade.

Some of the freeze damage was hardly surpris- ing, although we did have our fingers crossed. The eucalypts were all killed to the ground but are coming back vigorously. Certain buddleias, evergreen cotoneasters, escallonias, and various rhododendrons in the more tender subgenera and sections were killed to the ground as well. If these plants had been growing vigorously prior to the

Vol. 54:4 Winter 1991/1992

27

storm damage they should spring back from the base; however, weak plants may never recover. Another heartbreaking result of the storm is the damage incurred by some of the large, showy Himalayan magnolias, such as Magnolia camp- bellii. Some of these magnificent trees have been killed back to the central leader and may never at- tain the mature stature they once had. Our most severely damaged group of conifers was the true cypress ( Cupressus ) species. Some of these ap- peared as though they had been through a fire, but many are coming back with new growth from the shoot tips. Our Himalayan firs {Abies spec- tabilis) were completely defoliated with some stem dieback; these may not recover.

Some unexpected damage could be found among some genera and species ordinarily thought of as hardy. The mountain ashes {Sorbus spp.) suffered dieback in the cases of S. hupehen- sis, S. vilmorinii, and S. megalocarpa. Certain pines, such as Pinus wallichiana, and some junipers were severely burned. The widely sold Viburnum tinus was heavily damaged in the Ar- boretum, whereas certain other Asian evergreen species such as V japonicum and V henryi were hardly blemished — perhaps a phenomenon related to winter shade. Many of the Hinoki false cypress clones {Chamaecyparis obtusa) were badly dam- aged, yet the unknown and handsome Austro- cedrus chilensis was hardly touched.

Some notable survivals and recoveries include Eucryphia x intermedia ‘Rostrevor’, totally defoliated but recovering with little dieback, while E. x nymansensis ‘Nymansay’ is heavily dam- aged. Our spectacular Chilean fire tree, Emboth- rium coccineum , a scarlet-flowered gem without peer in the landscape and easy to reproduce from seed, came through the winter with only modest

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flower bud blast. Certain evergreen oaks, such as the compact and beautiful Quercus myrsinifolia from Japan and Q. hypoleucoides from the arid Southwest, performed as usual with nary a blem- ished leaf. One of our more handsome broad- leaved evergreen trees native to Oregon and Cali- fornia, Umbellularia calif ornica, has proved a very hardy subject through our recent cold spells.

Needless to say, as part of the role of the Wash- ington Park Arboretum, it is our business to observe and document the performance of plants in our collection. We shall continue to keep a close eye on the collection to assess potential la- tent effects of our 1990 freeze. (See also Ray Maleike’s article on preparing for winter damage, this issue.)

Please drop me a line at the Washington Park Arboretum or call (206) 543-8800 if you would like specific information about the performance of plants in the collection. Of course, you may ob- tain any plants mentioned here through the Arbo- retum Foundation’s Pat Calvert Greenhouse, open Tuesdays from 10-12.

Timothy C. Hohn is Curator of Living Collections for the University of Washington’s Center for Urban Horticulture and the Washington Park Arboretum.

Glossary

Cambial refers to the cambium, which is the plant tissue responsible for growth in diameter.

Physiologic drought is when an evergreen plant loses more moisture from its leaves than it is able to replace from its roots.

Wind-throw are trees blown over by high winds.

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28

Washington Park Arboretum Bulletin

For Further Information

by Valerie Easton

Where Can I Buy . . . ?

Tou’ve laid out your garden paths and bound- aries on graph paper, specified evergreens for backdrops and screens, and designated peren- nials in varying heights and colors for the border; you even decided upon a brown turkey fig for that sunny south comer against the wall. Or, you’ve hired a landscape designer who has specified mass plantings of a Sarcococca variety you've never heard of. And now’ it is time to plant. Where can you find the plants to fit into your landscape? Sometimes finding the desired plant material is the most difficult part of creating a garden.

Instead of wandering from nursery to nursery in search of that specific Sarcococca , you can use the wdde variety of material available to aid in lo- eating plants locally, nationally, and international- ly. There are monthly lists, specialized guides, and large directories listing thousands of different plants that fit your designs and specifications.

A good place to start is Plant Source, a monthly regional magazine published in Bellevue, Wash- ington, that lists trees, shrubs, and other herba- ceous and woody plants and where they can be found in western nurseries. Most listings include current information on size, quantity, and price of the plants at each nursery. For example, the Oc- tober 1991 issue tells us that Sarcococca hooker- iana var. humlis is available in both one-gallon and two-gallon cans at two Seattle nurseries in sufficient quantities for a mass planting.

Another regional guide is Hortus Northwest which is a new’ Oregon director)’ specifically for locating Northwest native plants. It has separate sections on wetland plants, trees and shrubs, perennials, and ground covers, and is especially valuable for locating hard-to-find natives.

When you w’ant to see a picture of what you're ordering and get an idea of costs, size, and quan- tities available, the best bet is to take a look at a nursery catalog. Many nurseries put out catalogs of their offerings, most often in spring and fall, varying from brief typcw’ritten lists to lavish full- color tomes. The Elisabeth C. Miller Library at the University of Washington Center for Urban

Horticulture has a collection of over 700 catalogs, indexed by plant and source. Included here are the large nurseries like Wayside Gardens and Burpee’s, and also many local and national specialty nurseries, such as: Aldrich Berry Farm in Mossyrock, Washington; Green Earth Organ- ics in Everett, Washington; Endangered Species in California; Limerock Ornamental Grasses in Port Matilda, Pennsylvania; and Roadhouse Nursery (aquatic plants) in Poulsbo, Washington.

A useful guide to these smaller local nurseries is the Specialty Nursery Guide , a free pamphlet issued each spring by Washington State’s Special- ty Nursery Association. The 1991 edition lists 34 nurseries from Federal Way north to Stanwood and east to Carnation, with specialties ranging from bonsai to kiwi.

There are several excellent national directories that can be used to identify nurseries that carry the plants or seeds you seek. Then you can locate the catalog in the library collection and read more about the nursery, seed, bulb, or plant before call- ing or w’riting to place an order.

The Andersen Horticultural Library 's Source List of Plants and Seeds , published in 1989, is a computerized listing of over 40,000 trees, shrubs, vines, perennials, herbs, annuals, vegetables, and fruits commercially available in North America. Look up your species or variety by its botanical name, then use the numbers next to it to refer to the nursery listing in the front of the book. To find the botanical name, you can look in the cross references for common names. For example, under “strawberry tree,” Arbutus w’ill be listed. Turning to the plant listing, you see that the compact type is carried by nurseries 718, 50199, 551164, and 51396. Also listed are the pages in their 1988-89 catalogs w’here the plant can be found. Turning to the list of nurseries at the front of the book, we see that 718 is ForestFarm in Williams, Oregon, and 50199 is Monrovia Nursery in Azusa, California. The Miller Library has current catalogs from both these nurseries. A new edition of this extensive directory is due out in fall 1992.

Other comprehensive national directories are:

Garden Seed Inventory , which contains all non- hybrid vegetable seed available in the United

Vol. 54:4 Winter 1991/1992

29

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Cornucopia : A Source Book of Edible Plants specifies sources for edibles from almonds to watermelons.

If you are planning a trip to the British Isles, three plant directories are useful. The Plant Finder , issued annually and published in associa- tion with the Hardy Plant Society, lists over 50,000 plants, including bulbs and fruit, and where to find them in the United Kingdom and Ireland. The Bernard E. Harkness Seedlist Hand- book lists alpine and rock garden plants offered by the seed exchanges of the major plant societies in America, England, and Scotland. The Green Pages: A Guide to the Nurseries and Garden Cen- tres of the British Isles is a descriptive listing by nursery, and also includes a listing by specific plant and type of plant. For example, it tells you which of 23 nurseries carries a good selection of alpine and rock plants, and which two to try if you specifically are looking for Lewisia.

Mail order gardening is becoming very popular and two such guides are invaluable: The Mail Order Gardener by Hal Morgan and Gardening by Mail , 3rd ed., by Barbara Barton. Barton’s book includes mail order sources for pest controls, garden furniture and equipment, and other ac- coutrements, as well as house plants, trees, shrubs, annuals, perennials, and vegetables of- fered by seed companies and nurseries in the United States and Canada. The listings here are more general than PlantSource or Andersen. If you’re interested in Iris , for example, you can find sources for 16 different types, iris societies in Washington State, and books about iris in this comprehensive catalog. Now we have a local guide, the NW Washington Gardeners ' Resource Directory , by Stephanie Feeney, which gives a good overview of educational and volunteer op- portunities in horticulture, resources, nurseries, literature, plant sales, gardens to visit, etc., in the region from Olympia, Washington, to Vancouver, British Columbia.

Additional sources for plants and seeds often are found in books on specific subjects. The Brooklyn Botanic Garden quarterly, Plants & Gardens , gives sources for plants in all its single topic issues. Special volumes in the last few years have included wild flowers and native plants, and herbs and ornamental grasses, with an issue

30

Washington Park Arboretum Bulletin

devoted to perennial sources ( Perennials : A Nursery Source Manual , winter 1988/89). A more current source for perennials is Perennials: Toward Continuous Bloom , which as a collection of pieces by current garden writers includes sources for their favorite perennials. Other books rich in sources are: The Combined Rose List 1991 , Miniature and Dwarf Geraniums , Garden- ing with Native Plants of the Pacific Northwest , and Azaleas. Whenever you’re reading a book about a particular kind of plant, check the table of contents to see if there’s a source list.

We are fortunate in the Pacific Northwest to have so many good nurseries, but we are by no means restricted to what they carry when we are doing our modern version of plant hunting. We

no longer need to go out into the wilds of China to find special plants, but rather can avail ourselves of the many directories, catalogs, and source books available for locating even the most unusual and scarce. Lest you think I exaggerate, Andersen Horticultural Library ’s Source List of Plants and Seeds lists sources for over a dozen Stewartia , 41 kinds oi Hypericum, over 1100 kinds of Chrysan- themum, and more than 2500 kinds of Hemero- callis.

Valerie Easton is a librarian at the Northwest’s foremost horticultural library, the Elisabeth C. Miller Library, University of Washington Center for Urban Horticulture. She has been the book review editor of the Bulletin since 1988.

New on the Shelves

of the Elisabeth C. Miller Library

by Valerie Easton

Booth, Norman K., and James E. Hiss. Residential Landscape Architecture: Design Pro- cess for the Private Residence. Englewood Cliffs, NJ: Prentice Hall, 1991. ISBN 0-13-775354-3.

Grenfell, Diana, and Roger Grounds. The White Garden. North Pomfret, VT: Trafalgar Square Publishing, 1990. ISBN 0-94395 5-36-X.

Imes, Rick. The Practical Botanist. New York: Simon & Schuster, 1990. ISBN 0-671-69306-9.

Ingwersen, Will. Alpines. Portland, OR: SagaPress/Timber Press, 1991. ISBN 0-88192- 193-9.

Jones, Pamela, and Bob Johnson. Just Weeds: History, Myths, and Uses. New York: Prentice Hall Press, 1991. ISBN 0-13-514118-4.

Lacey, Stephen, and Andrew Lawson. Scent in Your Garden. Boston: Little, Brown and Com- pany, 1991. ISBN 0-316-51169-2.

Metheny, Dorothy. Hardy Heather Species. Seaside, OR: Frontier Publishing, 1991. ISBN 0-939116-31-6.

Oklowski, William, Sheila Darr, and Helga Olkowski. Common-Sense Pest Control. New-

town, CT: Taunton Press, 1991. ISBN 0-942391-63-2.

Osborne, Robert, and Beth Powning. Hardy Roses. Pownal, VT: Storey Communications, 1991. ISBN 0-88266-739-4.

Pollan, Michael. Second Nature: A Gardener ’s Education. New York: Atlantic Monthly Press, 1991. ISBN 0-87113-443-8.

Preston-Mafham, Ken, and Rod Preston- Mafham. Cacti: The Illustrated Dictionary. Lon- don: Blandford, 1991. ISBN 0-7137-2092-1.

Proctor, Rob, and Rob Gray. Perennials: Endur- ing Classics for the Contemporary Garden . New York: Harper & Row, 1990. ISBN 0-06- 016315-1.

Reich, Lee. Uncommon Fruits Worthy of At- tention: A Gardener's Guide. Reading, MA: Ad- dison-Wesley Publishing, 1991. ISBN 0-201- 52381-7.

All of these books can be found in the Elisabeth C. Miller Library, Center for Urban Horticulture, University of Washington, Seattle. Call (206) 543-8616 for information on current hours.

Vol. 54:4 Winter 1991/1992

31

Book Review

SIVA ELIOVSON / FOREWORD BY ROBERTO BURLE MARX

The Gardens of Bnbetto Burle Marx. Sima Eliovson. Saga Press/Timber Press, Portland, Oregon. 1991. 23 7 pages. ISBN 0-88192-160-2. S45.00

he name Roberto Burle Marx brings to mind images of richly textured gardens, sweeps of contrasting foliage surrounded by the verdant landscape of Brazil, and modernist ab- stract paving patterns. His interest in horticulture and garden design was a hobby for a young artist in the 1920s. Ironically, he discovered Brazilian flora while studying art in Berlin. This interest blossomed into a life-long passion. Trained as an artist, Burle Marx's use of plants distinctly breaks with the earlier Brazilian colonial gardens in- fluenced by the French and Portuguese. His gardens represent a cornerstone of modernist design in landscape architecture. His work has

been inextricably linked with our images of Brazil in this century.

The Gardens of Roberto Burle Marx provides an introduction to Burle Marx and his work. The photographs and drawings illustrate the diversity of his work and his skill in the use of native plants to create gardens of a rich sculptural and textural nature. The gardens are presented in a roughly chronological order, allowing the reader to trace the development of his design skills. The reader also can follow the evolution of his increasingly bold use of plants and land form. In his work, the surrounding landscape is used as part of the garden, erasing the sense of edges and limits. The residence of Luis Cesar Fernandez is an example. His growing interest in the ecology of Brazil is il- lustrated by an increased use of native plant groupings which reflect native plant associations and habitat requirements. Marx’s interest in native plants resulted in the establishment of a nursery where he could propagate plants for use in his gardens. In the back of the book is an index of plants mentioned in the text and a listing of significant projects.

As an introduction to Roberto Burle Marx, the book encourages further reading and a possible trip. It takes a strong will not to want to walk through the gardens and hear the sounds of leaves on leaves and smell the vegetation as the sun evaporates the morning dew. It makes the reader rethink an approach to our Northwest region and our native plants. — Reviewed by Barbara Swift

Barbara Swift is a landscape architect and has recent- ly completed an essay for the Seattle Arts Commission Public Art Collection Catalog. She has written articles for Landscape Architecture and Arcade. Barbara is a new member of the editorial board of The Washington Park Arboretum Bulletin.

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