ELISABETH C. MILLER LIBRARY UW BOTANIC GARDENS Box 354115 206-543-0415 ^5 Seattle, Washington 98195-4115 Published by the Arboretum Foundation Spring 2007 $5 The Washington Park Arboretum Bulletin is a benefit of Arboretum Foundation membership. For information on membership or advertising opportunities, contact the Arboretum Foundation at 206-325-4510 or gvc@arboretumfoundation.org. Washington Park Arboretum The Arboretum is a 230-acre dynamic collection of trees, displaying internationally renowned collections of oaks, conifers, camellias, Japanese maples, hollies and a profusion of woody plants from the Pacific Northwest and around the world. Aesthetic enjoyment gracefully co-exists with science in this spectacular urban green space on the shores of Lake Washington. Visitors come to learn, explore, relax or reflect in Seattle’s largest public garden. The Washington Park Arboretum is managed cooper- atively by the University of Washington and Seattle Parks and Recreation; the Arboretum Foundation is its major support organization. Graham Visitors Center Open 10 am — 4 pm daily; holidays, noon — 4 pm. Closed University of Washington holidays. The Arboretum is accessible by Metro Transit buses #11, #43 and #48. For more information: www.transit.metrokc.gov University of Washington The University of Washington manages the Arboretum’s collections, horticultural programs, facilities and education programs through the University of Washington Botanic Gardens. It owns some of the land and buildings. 206-543-8800 voice / 206-616-2871 fax Office hours: 10 am — 4 pm weekdays www. uwbotanicgardens . org David J. Mabberley, M.A. (Oxon.), Ph. D. (Cantab.), Director, University of Washington Botanic Gardens Seattle Parks and Recreation The City of Seattle owns most of the Arboretum’s land and buildings. Seattle Parks and Recreation is respon- sible for park functions throughout the Arboretum and manages and operates the Japanese Garden. 206-684-4556 voice / 206-684-4304 fax Betty Jean (“BJ”) Brooks, Interim Superintendent — Washington Park Arboretum Bulletin Lee Cuninggim Neff, Editor Cynthia E. Duryee, Copy Editor Constance Bollen, Graphic Design Joy Spurr, Photography (unless otherwise noted) Arboretum Foundation The Arboretum Foundation is a nonprofit organization established in 1935 to assure the continued existence and flourishing of Washington Park Arboretum. The Foundation provides funding, volunteer services, membership programs and public information in support of the Arboretum, its plant collections and programs. Volunteers operate the gift shop, conduct major fund- raising events, and further their gardening knowledge through study groups and hands-on work in the green- house or on the grounds. 2300 Arboretum Drive East, Seattle, WA 98112 206-325-4510 voice / 206-325-8893 fax gvc@arboretumfoundation.org www . arboretumfou ndation . org Office hours: 8:30 am — 4:30 pm weekdays Gift shop hours: 10 am — 4 pm daily Officers of the Arboretum Foundation Board of Directors Neal Lessenger, Interim Executive Director John Johnston, President Susan Black, Vice President Fred Isaac, Vice President Mary Ann Odegaard, Vice President Judy Phillips, Vice President Tim Diller, Treasurer Della Balick, Secretary Neal Lessenger, Immediate Past President Editorial Board Cynthia E. Duryee, Writer/Editor Val Easton, Writer Polly Hankin, Edmonds Community College Daniel J. Hinkley, Author, Lecairer, Horticultural Consultant Steven R. Lorton, Former Northwest Bureau Chief, Sunset Magazine Ciscoe Morris, Horticulturist Myrna Ougland, Two Cats Nursery Pam Perry, Parsons Public Relations Christina Pfeiffer, Horticulairal Consultant Richie Steffen, Coordinator of Horticulture, Elisabeth C. Miller Botanical Garden David SUeatfield, University of Washington Dept, of Landscape Architecture Brian R. Thompson, Curator of Horticultural Literanire, University of Washington Botanic Gardens Cass Turnbull, Plant Amnesty Founder Martha Wingate, Writer Phil Wood, Garden Designer & Writer Botanical Editors Randall Hitchin, Registrar & Collections Manager, University of Washington Botanic Gardens Martha Wingate Spring 2007 Volume 69. Issue 1, © 2007 The Arboretum Foundation. ISSN 1046-8749. 2 Stewardship — Neal Lessenger 3 Cascara: Frangula purshiana — Walt Bubelis 0 Things I Learned from Dr. Shigo— Cass Turnbull 13 Britt Smith & Frank Mossman: On the Trail of the Western Azalea — Richie Steffen & Rick Peterson TENTS \ (y Epimediums: The Stars of the Spring Garden — Richie Steffen 21 The Flora of Seattle in 1850 — Part II — Ray Larson 27 Cascadia — Daniel J. Hinkley 30 In a Garden Library: Cascadia in the Miller Library — Brian R. Thompson , Bulletin Book Review Editor ABOVE: The Pacific dogwood, Cornus nuttallii, blooms in spring from Northern California to British Columbia and as far west as Idaho. Its red fruit and reddish-pink fall color make coming upon healthy wild specimens a hiker’s treat, either in spring or fall. Unfortunately, this native dogwood is susceptible to dogwood anthracnose, a non-native fungal disease that has killed many trees. To see healthy plants in the Arboretum visit grid locations 3-5E and 6-4E. ON THE COVER: The creamy-white blooms of Magnolia sieholdii face downward, the petals surrounding chocolate- to rose-red stamens. Flowering in May and June, this 10- to 20-foot small tree enjoys fertile, moist, well-drained soil. In fall, golden-yellow leaves contrast with red fruit. Native to southeastern China, Korea and Japan, and selected as a Great Plant Pick, M. sieholdii may be seen at Arboretum grid locations 27-3E, 27-4E and 28-3E. Spring 2007 °*> 1 COURTESY OF THE RHODODENDRON SPECIES BOTANICAL CARDEN Stewardship uch has been made of steward- ship of Washington Park Arboretum. All three partners involved in the Arboretum’s governance claim to be its stewards in their mission statements and elsewhere, yet stewardship has been an overused term for several years. “The Merriam-Webster Dictionary” defines stewardship as follows: 1: the office, duties, and obligations of a steward; 2: the conducting, supervising, or managing of something; especially: the careful and responsible management of something en- trusted to one’s care stewardship of our natural resources> If stewardship is roughly equated with supervision or management, then the steward- ship of Washington Park Arboretum rests squarely with the University of Washington. The 1934 agreement between the University and the City of Seattle entrusted the care of the Washington Park Arboretum to the University, and the University has been respon- sible for its management ever since then. The City has been responsible for the management of Washington Park, including all of the park elements (e.g., lawns, roads and pathways) of the Arboretum. A 1974 modification of the 1934 agreement did not change the City’s and the University’s roles, but it did provide that the costs of operating the Arboretum would be shared equally. Then what is the role of the Arboretum Foundation? The 1934 agreement called for the formation of a foundation to provide funds for the management of the Arboretum and for the collection of trees, shrubs and seeds. The Foundation was incorporated the following year to do just those things and to be a source of volunteers and advocates for the Arboretum. Today, the Arboretum Foundation is conducting a strategic planning exercise. While that work is not yet complete, it is apparent that the Foundation’s role will continue to be one of building community support for the Arboretum, advocating and promoting the Arboretum, and pro- viding private funding for Arboretum programs the Foundation wishes to foster, until such time as the managing partners fund those programs themselves. I suggest that instead of providing stewardship, the Arboretum Foun- dation is assuring the continued existence and flourishing of Wash- ington Park Arboretum. ^ Interim Executive Director, Arboretum Foundation The largest collection of Rhododendron occidental selections in the world, the Smith-Mossman Western Azalea Garden, includes this beauty, known as SM502 'Humboldt Picotee,’ and is located in the Lake Wilderness Arboretum in Maple Valley, Washington. To learn more, see the article beginning on page 13. 2 v* r> Washington Park Arboretum Bulletin Cascara: Frangula purshiana By Walt Bubelis Qtf, | hat is there not to like about this tree? It has kept families from desperate measures, has been used in practical jokes, is a native source of food for wildlife, is basically pest free and, to top it all off, has beautiful fall color. ABOVE: The bright green leaves of Frangula purshiana (syn. Rhamnus purshiana) show off the small dusty-yellow flowers that bloom from April through June. INSET: A close-up view of a cascara (F. purshiana) flower cluster. Cascara shrubs can be found among the Arboretum’s plantings of Northwest natives. Spring 2007 3 IMAGES THIS PACE COURTESY OF BEN LEGLER, WTU IMAGE COLLECTION The author’s cat, Mr. Parker, seems less interested in admiring the trunks of Frangula pursbiana than in exploring other sections of the Bubelis garden. The remarkable plant with all of these characteristics is none other than our cascara, Frangula pursbiana (syn. Rhamnus pursbiana) . A variation on its common name, cascara sagrada or “sacred bark,” refers to its use as a laxative. During the Great Depression, harvesting the bark kept many a family from falling into debt, although so much harvesting occurred during this time that the plant disappeared from many areas. Once the bark was stripped from a limb or trunk, that portion of the plant would die. Less desperate harvesters would not girdle the main trunk, leaving a strip of bark to continue life processes and perhaps regenerate new bark. Harvested bark, either fresh or dried, was sold to wholesalers, who then passed the aged bark on to pharmaceutical or herbal firms. Luckily for the distribution of cascara, birds relish the juicy fruits — pea-sized black berries — and spread them around the surrounding forest. Cascara also has the ability to sprout from a cut stump. Oh! Wondering about the practical joke? At the college where I did my undergraduate studies, a chap regularly received shipments of cookies from home. These he shared with his friends. If he didn’t get to his mail promptly, however, he would find his cookie package pre-opened and rifled. To determine the culprit, he asked his mother to send him a specially marked box that would have cascara powder mixed into the cookie dough. Needless to say, the culprit wisely avoided cookie shipments after that. One last warning: Do not use a cascara branch to toast marshmallows on a picnic! Northern California Indians introduced the use of cascara to early 16th century Spanish explorers. Other tribes, ranging from the Pacific Coast to the Kootenai and Flathead of western Montana used it as a laxative, consuming it as a tea brewed from the bark. Although the Food and Drug Administration has removed cascara from both non-prescription and prescription use in the United States, it is still sometimes used as a dietary supplement. Frangula purshiana: Range and Growth Habit Cascara is found from southern British Columbia to western Montana and Idaho, and south through the Cascades into central California, ranging from sea level to 6,000 feet in altitude. With this wide distribution, it should come as no surprise to find it in a number of diverse habitats including canyons, bottom- lands and dower mountain slopes. Other wildlife will browse it, but only coastal deer seem to find it truly palatable, limiting its use as a landscape plant in some coastal areas. Cascara prefers moist soils but is so tolerant of drier sites that it can be characterized as a competitive colonizer in some areas. It associ- ates as easily with floodplain species as it does 4 Washington Park Arboretum Bulletin PHOTO BY WALT BUBELIS PHOTO BY WALT BUBELIS The shades of gray mottling on the bark of cascara sagrada give it an interesting snake-bark effect. with coniferous plants and dry-land plantings such as chaparral. Although shade tolerant cascara’s fall coloration can be — if given a sunny location — a gorgeous butter-yellow that literally glows. Big-leaf (or Oregon) maple (Acer macropbylluni) is its only competitor. Cascara averages 30 feet in height, with exceptional specimens reaching 70 feet. Although it normally grows vertically, it can be found leaning at odd angles when grown in excessive shade, since weaker stems are more pliable. In shade, it often stays evergreen. With four- to six-inch, smooth-margined, oval- shaped leaves and small clusters of flowers, it doesn’t stand out amongst its native compan- ions unless isolated or in fall color. Once established, cascara has few pests other than occasional leaf beetles. In California and Oregon, it has been recorded as a host for the pathogen Phytophthora ramorum , mislead- ingly called “sudden oak death.” The impact that serving as a host for this disease is having on native stands of cascara is being monitored. Gifts to the Gardener Cascara is available at a number of nurseries carrying native plants. Youngsters are easy to transplant. I have successfully moved bare-root specimens up to six feet tall. Gathering seed in late summer and sowing them, without their pulp, one inch deep, before winter, is another successful propagation method. As a member of the buckthorn family, Rhamnaceae, cascara shares a valuable trait that allows it to estab- lish itself in barren soils: It produces nitrogen-forming nodules on its roots. Dig up a few root tips, and you will observe clusters of small tan to yellow, bacteria-laden nodules that absorb atmospheric nitrogen and convert it to a solid form, such as amino acids — the building blocks of proteins — which the host plant can use. Only when the host tree is dead will the nitrogen become available to its neigh- bors. Pioneer species with this nitrogen-fixing talent thus have a leg up on the competition. (Also in this family of plants with root nodules, Ceanotbus species are quite common in Northwest gardens.) One last note concerning cascara’s landscape value: Its bark is much underap- preciated. Young tree trunks up to five inches in diameter exhibit a series of light-colored diamonds against the otherwise smooth, gray bark — a snake-bark effect that is quite striking. Cascara is not a prima donna in the plant world, but it does serve well in a number of supporting roles: providing food for wildlife, supplying nitrogen for the soil and offering quiet beauty. ^ Walt Bubelis has taught horticulture at Edmonds Community College for 38 years. Spring 2007 5 PHOTO BY CHRISTINA PFEIFFER Things I Learned from Dr. Shigo By Cass Turnbull Drawings by Kate Allen n October 6, 2006, a great man, Dr. Alex L. Shigo — who was born in Pennsylvania on May 8, 1930 — died of a head injury suffered in a fall at his summer home. News of Dr. Shigo’s accident spread quickly through the arboricultural community here and abroad. And, like many others, I was personally stunned and saddened by the news. Since then, I have been surprised to realize how many horticulturists are unaware of his groundbreaking work. Shigo was described as the “Sir Isaac Newton of Trees.” I find that an apt description. From Shigo, I gained an understanding of how trees deal with injury and decay; how they are engineered — which is to say, how a branch is attached to the trunk; and where trees’ roots really are and what they need. I attended many of Shigo’s workshops and lectures over the past twenty-three years — the first when I worked as a grounds maintenance person at Seattle Parks and Recreation, long before I knew I had a special relationship with trees, and years before PlantAmnesty. It was a free class, and I thought, “What the heck? I like to learn.” I couldn’t understand much of Alex Shigo, the “Sir Isaac Newton of Trees,” mesmerizes a class of eager students. 6 Washington Park Arboretum Bulletin what Shigo said, but I could tell I was in the presence of greatness. Shigo had a bad habit of assuming a certain base level of knowledge in his audience. Of course, even this base level did not exist in my case. He kept talking about “compartmentalization of decay in trees” or the CODIT model for short. I kept wondering why anybody would care. After the big storm this winter, I daresay more people do! Avoiding Failure: Good Medicine for Trees The background for all discussion of trees is that they are a long-term proposition, so we need to manage trees for their long haul and for our safety. This puts trees in the same class as bridges and skyscrapers. We are inter- ested in preventing and assessing the decay (or rot) in trees, because trees with massively rotten trunks break (trunk failure), and trees with root rots (common in the Northwest) blow over (tree failure). The third common classification of tree “failure,” as it is called, is a broken or shed branch. When arborists do “risk assessments” of trees, they look at the most likely point of failure (trunk, entire tree, branch), the weight of the part that will fail, and the relative absence or presence of a target. A tree that will fall in the woods poses almost no risk, since it will not strike anything valuable. A road, a parking lot or a backyard have a medium target rating, because, at any given moment, a person may or may not be there. A permanent structure, like a house, rates highest, because it is always in harm’s way. There is no modern medicine for trees. We now have access to a few new diagnostic tools — some imperfect x-ray machines for trunks and some root excavation devices (air- spades) — but we have no “miracle cures,” no tree penicillin. Medicine for trees remains as it was for humans in the 19th century, mostly preventive: stay healthy and avoid injury. Decay enters a tree after an injury, like gangrene after a war wound. Once a tree is injured, it will react chemically, trying to “wall- off” the infected area and outgrow the injury. This reaction, known as “compartmentaliza- tion,” follows known patterns in trees. Compartmentalizing Injury As a Shigo devotee, I now have a more accurate picture in my mind of what the inside of a tree trunk looks like. Instead of pockets of rot, I see columns. People who have attended Shigo’s lectures and read his textbooks also see the history of a tree’s wounds when they look at your wooden coffee table. In the CODIT model, we find that decay is confined to the “wood present at the time of wounding.” When you see a hollow tree, the hollow is the exact size the tree was when it was topped or otherwise damaged. The sound wood — indicated by the rings of the tree that grew after the injury — is safe and sound. This is one reason a young tree can withstand a lot of injury, and an old tree, very little. A topped 10-year-old tree might be expected to rot entirely to the ground in the next five years, but, in reality, it will quickly add new rings of sound wood and will be as strong as a thick-walled pipe. By the time the tree is old, the slender rotten core will be a relatively small part of the tree trunk. But if a 50-year-old tree is topped, it will develop a relatively large internal decay column surrounded by a thin outer ring of new sound wood. The “take-home messages,” as Shigo called them, are as follows: All pruning wounds trees. Trees do not “heal” like animals. They “compartmentalize” their injuries. Trees wall off the damaged area with chemically altered wood and outgrow the injury. Pruning the right way, by making removal cuts to the collar (where the branch joins the trunk or a larger branch) in the right amount (not too big, not too many, and less on old trees), minimizes the damage and maximizes the safety, health and longevity of trees. Pruning paints and “wound dressings” don’t work. Taink injuries are the worst. Branch injuries Spring 2007 7 are the easiest to compartmentalize. But avoid all unnecessary wounds to the trunk, the limbs and the main roots of trees. When a cavity is seen in a tree, do not carve back into live wood and fill it, as was once commonly done. That breaks a “wall,” sending in a new invasion of rotting organisms. Similarly, we no longer drill to drain water out of cavity, as that wounds previously protected wood. Trunks & Branches: Laminated Layering “Trunk wood is different from branch wood,” were words Shigo repeated again and again. He explained how branches are attached to the trunk and why they are so strong. Engineers had long been amazed by the ability of a tree’s limbs to withstand wind stresses and snow loads. I once saw a photo of a very large tree that withstood the Hiroshima blast. It was leafless but still standing when every- thing else in sight was rubble. When the stress is too great for a limb, or when it is damaged, the tree sheds the limb without the rest of the trunk being affected. When illustrating how a tree limb is attached to the trunk, Shigo described a process somewhat like lamination. A limb is made up of wood different from that of the trunk. The only part where the wood is “co-owned” is a small tag at the underside of the branch. This 8 v*o Washington Park. Arboretum Bulletin BOOKS BY ALEX L. SHIGO Readers interested reading books written by Dr. Shigo might look for the following books at local libraries, booksellers or on-line: “A New Tree Biology Dictionary: Terms, Topics, and Treatments for Trees and Their Problems and Proper Care” (1989); “Modern Arboriculture: A Systems Approach to the Care of Trees and Their Associates” (1991); and “100 Tree Myths” (1993). is all very hard to visualize but was best described to me when explained as follows: In the spring the branch wakes up first and puts on a layer of new wood — this year’s ring. Then the trunk wakes up and puts on a layer of trunk wood. Where the two meet, at the base of the branch, one finds a layer of trunk wood, overlapping a layer of branch wood, in succession. The bulge of alternate layers of wood is called the branch collar. The branch is actually embedded in the trunk, back to where it began as a bud, but it is not made up of the same wood. When you see a knothole drop out of a piece of lumber, that is part of a branch. Thus, Patterns of decay from A. stub, Perennials Annuals Grasses Shrubs Herbs Saturday, April 28 TO AM — 5 PM Sunday, April 29 TO AM — Member Pre-Sale & Party Friday, April 27 Warren C. Magnuson Park Special Events Center (Bldg. 27) Lots of Free Parking Benefits Washington Park Arboretum 206.325.4510 www.arboretumfoundation.org Dozens of Nurseries & Vendors! April 14 Early Bloomers PLANT/SALE TO AM — 2 PM Graham Visitors Center Spring 2007 9 Branches die back naturally to the collar. The collar is usually oibvious as a bulge. we all learned from Shigo to cut to the collar, but not into it, as that would wound the trunk, allowing an entirely different column of decay to develop. Alternatively, cutting too far away from the collar, leaving a stub of deadwood, is also bad. The stub acts like a “stick of sugar,” defenseless food that attracts rot-organ- isms to the tree. So “flush cuts” are out; “stub cuts” are also bad, and “collar cuts” are in. The horticulturally correct gardener will spend a fair amount of time and energy reading about collar cuts — learning how to make proper cuts and learning where the collar is, exactly, on trees where it is not obvious. To Avoid Limb Failure, Prune Properly An interesting bit of news from Shigo is that most of the damage to property and people that is -caused by trees comes from limb failure, not from the blow-down during windstorms, as is commonly supposed. And limb failure is often caused by improper pruning, including flush cuts and tree topping cuts. A branch that re-grows after a topping cut does not have the physical integrity of the original limb that was embedded in place with many layers of sound wood. The new limb growing from a topping cut is sort of scabbed on the outside and is often attached to an adjacent pocket of rot in the trunk. Take home messages: topping and heading cuts are the most difficult cuts for trees to compartmen- talize; a new branch grown after topping is apt to be weakly attached, even many years later when it is larger and heavier; and removing a limb by cutting to the branch collar minimizes the damage to trees. Where Are the Roots? Dr. Shigo also cautioned, “Tree roots aren’t where you think they are.” Most of us have an inaccurate picture in our heads of where a tree’s roots are. Some believe that trees are held up by a long taproot, one that looks sort of like a carrot; or, equally inaccurate, we believe that a tree’s roots look like a mirror image of the crown — the entire above and below ground portrait resembling a barbell. That misinformation has been copied from one text to the next over the course of decades and sometimes even centuries. Shigo liked to trace back the origins of such misinformation. He showed us how it is reinforced by a hundred logos and product labels, such as those on fertilizer bags. Tree roots come in an amazing variety of sizes and configurations, including some very strange ones growing in the tropics. But, on average, they are relatively shallow and stretch far beyond the drip line of trees. The more 10 Washington Park Arboretum Bulletin ROOTS: What we think (left), reality (right). accurate mental image of a tree, above and below the ground, is that of a goblet sitting on a plate. Most of the average tree’s roots are in the top three feet of soil and, of those, the fine, absorbing roots are in the top few inches. Some tap roots and some “sinker roots” exist, but a tree is held up mostly by the weight of soil it holds in the entire labyrinth of its roots, like a floor lamp that is held up by a heavy base. Where Tree Roots Will Grow Before becoming a Shigo student, I also wrongly pictured tree roots radiating evenly from the trunk, like spokes on a wheel. They actually vary greatly and spread out unevenly, according to whether or not they find what they need. An old saying of arborists is, “Tree roots go where tree roots will grow.” And what roots want is air, not water, as I had assumed. Water, it turns out, travels laterally, not just straight down. But cut off the air supply by compacting the top three inches (by filling with soil, flooding, or covering it with concrete), and the tree will slowly suffocate. Even the structural roots are nearer the surface than generally imagined and are thus frequently severed by construction workers digging foundations or burying cables and pipes. They have a different picture in their heads of where the tree roots are — the wrong picture. Enlightened construction techniques tunnel under tree roots when nearing what is called “the critical root zone,” the area which must be guarded if the tree is to survive nearby construction. Root damage from construction, like a war wound, sets trees up for the many root rots common in our area. And it is root rots that cause many a tree to blow over in the storms that seem to plague us with greater and greater frequency. After a storm I am apt to pull over to investigate a toppled tree on the side of the road. I feel its upturned base for mushy roots, check the trunk (and the origi- nating wound) for decay and look for the presence of a large girdling root. Of course, all of this is realized after the tree has failed and after Shigo has shown how that failure might have been prevented. Cass Turnbull is the founder and spokesperson for PlantAmnesty, a Seattle- based nonprofit organization that endeavors to promote respect for plants and to educate the public about proper pruning techniques. Further information is available at plantamnesty.org. She is the author of “Cass Turnbull’s Guide to Pruning” (2nd edition, Sasquatch Press). Spring 2007 11 TOP LEFT: The brilliant fall color of the foliage of Rhododendron occidentale growing wild in the Siskiyou Mountains. Here it is seen with the hooded flowers of Darlingtonia californica , the West Coast’s native pitcher plant. TOP RIGHT: The remarkable blossom color of SM 232 ‘Leonard Frisbie,’ named for the man who inspired Britt Smith’s and Frank Mossman’s work. BELOW: SM 157 ‘Miniskirt’ with its red, protruding stamens and styles. 12 'jo Washington Park Arboretum Bulletin Britt Smith & Frank Mossman ON THE TRAIL OF THE WESTERN AZALEA By Richie Steffen and Rick Peterson here are seldom times when someone gets the chance to “define” a plant in horticulture. The level of commitment must be high, and the will to overcome any obstacle, great. Fortunately, our region seems to draw such individuals and inspire them to go beyond the ordinary. Britt Smith and Frank Mossman are two such men, and their passion is to better under- stand our West Coast native deciduous azalea, Rhododendron occidentale. They were inspired by the exhaustive work of Leonard Frisbie, a nurseryman from Tacoma, Washington, who compiled over 10 years of research on the western azalea in the 1950s. Frisbie’s work represented the first serious study of this azalea since the species was first collected more Britt Smith than 90 years earlier. Smith and Mossman took up Frisbie’s work and strove to show the full range of diversity within this species. The two men started their journey in 1966, and over the next 15 years discovered and documented over 200 unique and interesting forms of the western azalea along the southern coast of Oregon and Northern California. Rhododendron occidentale: Showiest of Shrubs What was it about this plant that intrigued them? Its spectacular floral display played a major role in capturing their attention. Rhododendron occidentale is one of our showiest native West Coast shrubs. The flower corolla (the funnel-shaped bloom) is typically Frank Mossman The “freak” SM 53 with ribbon-like foliage. Spring 2007 13 white or flushed pink and is covered with characteristically sticky glandular hairs. When fully open, the corolla has five lobes (petal- like divisions). Generally, the lobes are all white with the top lobe sporting an orange- yellow blotch. Flowers can be as large as four inches across, and they average two to three inches wide. Combine this with highly fragrant blooms, and it is easy to see why Smith and Mossman devoted so much time to this plant. This hardy azalea is an easy-to-grow species that thrives in our Northwest gardens. A relatively slow grower, it will reach four to five feet tall in 10 years with mature specimens becoming seven to eight feet tall with time. Old specimens in Azalea Park in Brookings, Oregon, are thought to be over 100 years old and are at least 15 to 20 feet tall. Once estab- lished, the western azalea will tolerate drought; however, the stress does make it prone to powdery mildew. Regular water during dry weather and a location with good, well-drained garden soil and full sun to partial shade will help to minimize this problem. Smith and Mossman took great care with recording their findings, leaving quite detailed notes. Many of their selections can still be located in the wild by using the information found in their records. When an unusual form caught their attention, notes were taken on the location, bloom time and flower details, including color, size, number per truss and any unusual features. Each unique rhododendron received its own record number — most of these were Smith-Mossman numbers typically written as “SM#.” Out of this fantastic array of very desirable plants, only a handful were given cultivar names — with one of the most beautiful, SM#232, or Rhododendron occiden- tal ‘Leonard Frisbie,’ named after the person who inspired them. Following is a brief summary of the scope of their work in Britt Smith’s own words: "Rhododendron occidental is thought to have been first reported in a publication by Sir William Hooker in 1857, and he credits its discovery to a Mr. Gray. [Authors’ note: Mr. Gray refers to Asa Gray who first described R. occidental. An herbarium specimen of R. occidentals was most likely collected by George Tradescant Lay, the naturalist on the English sailing ship Blossom, under the command of Captain Frederick Beechy. The Blossom left England in 1825, returning in 1828.] The first seeds were taken to England by Mr. William Lobb, who landed in San Francisco in the summer of 1849. The first Rhododendron occidental bloomed in England in the garden of Mr. James Veitch of Exeter in 1857. It is likely that the great fragrance of the species was the reason for its first use in hybridizing. It was crossed with the 'Ghent azaleas/ and after much inbreeding produced the now well-known Knaphill and Exbury azaleas. Subsequent hybridizing continues in many places, combining and recombining Rhododendron occidentale with Knaphill- and Exbury-type azaleas, resulting in great beauty and often fragrance. "In the United States, Rhododendron occidentale seems to have received little atten- tion until 1952, when Mr. Leonard Frisbie began his monumental effort of investigating the species, regarding which he reported in the quarterly publication of the Pacific Rhodo- dendron Society, Rhododendron. His was an effort of dedication with no monetary reward. There were years of research and inquiry in libraries, at universities, and in the field. He made many trips by public conveyance to hunt, inspect, select, and mark outstanding plants. There were winter trips with his friend, Dr. Charles S. Berry, to collect layers and plants. "The January 1961 issue of Rhododendron and some of the plants collected by Mr. Frisbie had come to the attention of Dr. Frank Mossman of Vancouver, Washington, who then invited me [Authors’ note: Britt Smith was from Kent, Washington.] to join him in continuing Mr. Frisbie's investigation. Let us now review some of the results of our investigations. "We focused our attention to the area which 14 •jo Washington Park Arboretum Bulletin had been designated by Mr. Frisbie as being the most promising. That designation was correct, and the area soon became known by us as 'Occidentale Land/ Roughly, the bound- aries are from Coos Bay to Roseburg to Grant's Pass to Klamath in Oregon, and on to Eureka in California, and the shoreline of the Pacific Ocean from Eureka to Coos Bay. and a very inviting place to pause. It soon became the hub of the investigations of Rhododendron occidental, and 'home away from home' for Dr. Mossman and myself. In Crescent City, at the junction of two roads, there was a large pasture where many collec- tions were made with the owner's permission. The plants are poisonous to grazing animals, "Crescent City is a small town on a beautiful bay near the northwest corner of California, continues on page 33 Britt Smith and Frank Mossman could not ever agree on the 10 best selections they found but often mentioned in articles some of their personal favorites: • SM 28, SM 28-1, SM 28-2, SM 28-3 — This group represents a small population of double- flowered plants found growing in an area no more than 50 feet in diameter in a location called Le Munion’s Pasture near Crescent City, California. Each selection bears 10 or more petals per flower. The best of the group, SM 28-2, was given the name ‘Crescent City Double.’ • SM 30 ‘Crescent City Gold’ — One of the best “yellows” found on their trips. Each lobe shows orange-yellow coloring. This selection later became a prominent parent in Britt Smith’s Rhododendron occidentale breeding program effort to develop a true all-yellow flower. • SM 53 — Referred to in Britt Smith’s writing as a “freak,” it has deeply cut lobes to the base of the flower, giving a ribbon-like appearance to each petal. • SM 148 — One of the largest flowering forms found. Each bloom is about four inches across with a crease down the center of each lobe, giving a slight twist to each petal. • SM 157 ‘Miniskirt’ — One of the smallest flowers discovered, only about one-half inch across. The stamens and styles protrude far beyond the petals and look like long legs beneath a petal miniskirt. • SM 232 ‘Leonard Frisbie’ — Considered the best selection they found, Rhododendron occiden- tale ‘Leonard Frisbie’ — named for the man who inspired them to seek out R. occidentale in the wild — has large flowers with a highly frilled edge to each lobe and is heavily colored with pink and white. • SM 502 ‘Humboldt Picotee’ — The best picotee they found, but a very unstable plant. One plant can sport three different sorts of bloom: a spectacular, vivid red-edged picotee flower, a slightly larger bloom with a fine line of red on the edge of each bloom, or an almost typical flower. Branches sporting the best and most dramatic flowers will also have the deepest green foliage marked with dark chocolate-red specks. It is very slow and extremely difficult to propagate. • SM 601 — A very heavy-blooming selection; each of its trusses contains over 50 flowers. • ‘Stagecoach Frills’ (no SM #) — Large, white-flushed pink flowers open with a prominent orange-yellow flare on the upper lobe. Each lobe is highly frilled, producing a delicate and lacy appearance. Found near the top of a hill in the area known as Stagecoach Hill. Spring 2007 15 wxa* 4 : p? \ C* % *4 ^ V m mi m/L . A.yv. lb* v$m s •v. '• If ABOVE: Epimedium x perralchicum, a hybrid of E. perralderianum and E. pinnatum ssp. colchicum, brings sunny life to dry shade, as do other epimediums derived from Mediterranean natives. INSET: Epimedium grandiflorum ‘Dark Beauty’ is one of the author’s favorite epimediums for foliage interest. 16 Washington Park Arboretum Bulletin The ^""^-he first epimedium I remember is likely (y the same one that almost every one first remembers. It had bright butter-yellow flowers in late winter or very early spring, soon followed by leathery dark evergreen foliage, and it likely grew in an older garden and was remarkably adapted to dry, shady locations. This reliable plant is well known to us but, oddly, is often sold under the wrong name. The plant I remember was almost certainly Epimedium x perralchicum , a hybrid of Epimedium x warleyense, with sprightly orange flowers, is a tough, drought-tolerant ground cover. Spring 2007 17 Epimedium grandiflomm ‘Queen Esta’ is one of the author’s favorites. It’s two-toned lavender and white flowers show up beautifully against its dark purple new foliage. As early foliage turns green, new flushes of purple foliage continue, creating a long-lasting show. E. perralderianum and E. pinnatum ssp. colchicum. But it is commonly sold as one of its parents and sometimes as a completely unrelated yellow-flowered species. It has always struck me as odd that a plant so well known in the garden is almost completely unknown by its correct name. I guess this situation stems from the fact that we are only now gaining a wider understanding of this remarkable genus. The primary recommendation of Epimedium x perralchicum is that it seems to RICHIE STEFFEN S EPIMEDIUM SHORT-LIST • The best epimediums for flowers: Epimedium bracbyrrhizum Epimedium epsteinii Epimedium franchetii Epimedium grandiflorum ‘Lavender Lady’ Epimedium grandiflorum ‘Orion’ Epimedium grandiflomm ‘Purple Prince’ • The best epimediums for foliage: Epimedium grandiflomm ‘Dark Beauty’ Epimedium grandiflomm var. higoense ‘Bandit’ Epimedium lishihchenii Epimedium myrianthum ‘Mottled Madness’ Epimedium x mbmm ‘Sweetheart’ (drought tolerant) Epimedium sempervirens ‘Cherry Hearts’ • The best epimediums for all around garden use: Epimedium ‘Black Sea’ (drought tolerant) Epimedium grandiflomm ‘Queen Esta’ Epimedium grandiflomm ‘Tama-no-genpei’ Epimedium grandiflomm var. thunbergiana ‘Yubae’ (also sold as ‘Rose Queen’) Epimedium sempervirens ‘Rose Dwarf Epimedium stellulatum Epimedium x versicolor ‘Cherry Tart’ (drought tolerant) Epimedium x versicolor ‘Versicolor’ (drought tolerant) Epimedium x warleyense (drought tolerant) 18 Washington Park Arboretum Bulletin thrive on neglect, but it is only one of several epimediums that have this reputation. These tough epimediums are all native to the Mediterranean or are hybrids strongly influ- enced by Mediterranean species. The Pacific Northwest climate — winter wet and summer dry, so similar to the Mediterranean — allows these plants to grow here with relative ease and little care. This group includes familiar plants, such as E. alpinum, E. pubigerum, E. x rubrum (a hybrid with E. alpinum as a parent), E. x versicolor (a hybrid between E. grandi- florum and E. pinnatum ssp. colchicum), and E. x warleyense (a hybrid of E. alpinum and E. pinnatum ssp. colchicum ). In the last decade or so, a flood of new species and selected clones — many originating in China — have arrived in the Northwest. When they first started to appear, there were minors of flowers over two inches across (enormous for an epimedium) and plants that would grow to three feet tall! As these plants have been trialed, we have been met with both thrilling success and lackluster disappointment, but many of the old rumors did hold true. There are new, huge-flowered forms, far larger than anything seen before. Last year a rare species, Epimedium latisepalum, bloomed — with white flowers, two inches across — and its admirers quickly dubbed it the “dinner-plate-dahlia” of epimediums! Collectors, both in the United States and in Great Britain, have chosen a number of new selections and created inter- esting hybrids using these new Asian species. Although these Asian species have added a fantastic new dimension to our gardens, they have one main drawback: They are native to areas with regular summer rainfall and will not tolerate our long dry summers without regular watering. The Elisabeth C. Miller Botanical Garden has been collecting various forms for many years and, as they have become established, has been evaluating their garden worthiness. In our observations, all epimediums prefer bright shade to half-day sun for the best flowers. Selections derived M Cioud Mounmn Farm Nursery, landscaping & Orchards Unique Plants for NORTHWEST GARDENS ornamentals, fruit, natives 6906 Goodwin Road, Everson • (360) 966-5859 www.cloudmountainfarm.com DIG Floral & Garden 19028 Vashon Hwy SW Vashon, WA 98070 206-463-5096 206-463-4048 fax web: dignursery.com email: dig@centurytel.nel Select Native ancC Hardy Free Horticultural Seminars and Special Events Woodinville • 13625 NE 175th Street • www.molbaks.com • 425-483-5000 • 1-866-466-5225 Arboretum Foundation Washington Park Arboretum 2300 Arboretum Drive East Seattle WA 98112-2300 www.arboretumfoundation.org NONPROFIT ORG. US POSTAGE PAID SEATTLE, WA PERMIT NO. 126 An arboretum is a living museum of woody plants for research, education, conservation and display.