Center for Urban Horticulture University of Washington Vol. 7, No. 3 Cooperative Extension Washington State University Summer 1989 LANDSCAPE MAINTENANCE SEMINARS . . . for the landscape professional Cooperating: Center for Urban Horticul- ture, University of Washington; Cooper- ative Extension, Washington State Univer- sity; Edmonds Community College; South Seattle Community College. Perennials for Northwest Landscapes • “Choice Perennials for the Northwest: Emphasizing Drought- and Heat-Tolerant Species” Bill Hielscher, Morning Glory Farms • “Ornamental Grasses and Companion Plants” Todd Paul, horticulturist • “Hostas” Don Smetana, A & D Peony and Perennial Nursery • “Design: Incorporating Perennials into Existing Landscapes” Rucy Nieman, landscape designer • “Maintenance: Are Perennials Practical in Commercial and Public Landscapes?” Susan Hanley, Evergreen Services Corp. Date : Thursday, July 27 Time : 6:30-9:30 p.m. (EVENING SEMINAR!) Fee : $12.50 preregistration $15.00 registration at door Registration form and information are on page three. PRO HORT Editorial Staff: Dr. John A. Wott George J. Pinyuh Van M. Bobbitt, editor Water Conservation Seminars with Robert Kourik Robert Kourik is a landscape designer, hor- ticultural consultant, and author from Occi- dental, California. His articles have appeared in Organic Gardening, National Gardening Magazine, Fine Gardening, Har- rowsmith, and Horticulture, and he wrote the book Designing & Maintaining Your Ed- ible Landscape Naturally. His new book, which he describes as “an idiot’s guide to drip irrigation,” is to be released in early 1990. Kourik has 12 years’ experience with drip irrigation. He became interested in xeriscaping out of necessity while operating a landscape business during California’s 1975-77 drought. I. Xeriscaping: Gardening As If Water Mattered As irrigation water becomes more scarce and expensive, the economic survival of the landscape industry may depend on doing more with less. Robert Kourik will cover practical methods of reducing landscape ir- rigation demands: soil preparation, mulch- ing, appropriate plant selection, gray water, efficient irrigation systems, and much more. Date : Thursday, August 10 Time : 8:30 a. m. -4:30 p.m. II. Drip Irrigation: A Step-by-Step Guide Drip irrigation can provide you with better looking landscapes for less effort. Robert Kourik notes that drip systems can reduce water use by 50 percent while increasing yields up to 84 percent. This program will provide you with the knowledge needed to design, install, and maintain the most effi- cient drip systems for ornamental land- scapes. With this information, landscapers can add a much-needed and marketable service to their business. Date : Friday, August 1 1 Time ; 8:30 a. m. -4:30 p.m. Fees : $35 per seminar $50 for both seminars Preregistration required! Register early! Water Quality and Horticultural Practices There is increasing concern about the pollu- tion of our lakes, rivers, oceans, and ground-water supplies. Horticulturists may be contributing to the problem as pesticides, fertilizers, and eroded soil end up in our water. How serious is the prob- lem? What can you do? Find out at this seminar. • “Understanding the Water Cycle” Dr. Craig Cogger, extension soil scientist, Washington State University, Puyallup. • “The Risk of Ground-Water Pollution by Agricultural Chemicals” Dr. Craig Cogger • “The Impact of Agricultural Chemicals and Erosion on Surface-Water Quality” Gerald Montgomery, conservation liaison, Water Division, United States Environmen- tal Protection Agency. This seminar qualifies for three hours of WSDA pesticide license recertification credit. Date : Tuesday, September 12 Time 9:00 a m. -12:00 noon Fee : $12.50 preregistration $15.00 registration at door Parking Prepaid parking is available in the Cen- ter for Urban Horticulture lots for those attending Pro Hort seminars. Please use the parking lots. Plant Palette: Stewartia pseudocamellia (syn. Stuartia) Timothy Hohn Center for Urban Horticulture University of Washington Visit the Washington Park Arboretum and take a close look at the stewartias. Take a particularly close look at Stewartia pseudocamellia and its variety koreana. In fact, you must look at these small trees dur- ing each season of the year. Yes, this is a transparent ploy to encourage you to visit the Arboretum more often, but indulge yourself this time. I dare you to be disap- pointed. I challenge you to find fault with the landscape character of this tree. The genus Stewartia contains six to eight species, two of these native to the south- eastern United States and the rest to eastern Asia. They belong to the same subdivision of the tea family, Theaceae, as Camellia. They range in size from large shrubs to small- or medium-sized trees. They all make wonderful landscape plants. The genus was first described by Linnaeus in 1746 after he received a portrait of S. malacondendron, an American native, from Isaac Lawson. The specimen portrayed was growing in the garden of John Stuart, Earl of Bute, whose name was unfortunately misspelled by Mr. Lawson in the dedication and therefore also adopted by Linnaeus in the description. Hence, my synonym in the title of this col- umn. Stewartia pseudocamellia, “Natsu-tsubaki” as it is known in its native Japan, is a decid- uous tree to 60 feet in the wild but 30 to 40 feet in cultivation. It is found wild in the mountains of Honshu, Shikoku, and Kyushu, and there is a Korean race often designated as a variety: Stewartia pseudocamellia var. koreana. What a lovely sight a native copse of these trees must be when in full bloom during midsummer. As you might guess from the specific name, the flowers are very camellia-like, with their large, white petals in groups of five, reveal- ing a golden center of incurved stamens. These buttercups are produced singly in the leaf axils on short stalks and may be 2^2 inches across. They make their appearance at a time of year, late June or early July, when most woody plants have already strutted their stuff. The new leaves are often reddish and be- come a lush green, sometimes with blue overtones, and prominently veined by the time the flowers appear. They form slender, pointed ovals about three inches wide and four inches long — a perfect background for the pearly flower buds and showy white buttercups. The show does not end here and, in fact, is hardly half over. The fall color is often a sloppy palette of mixed yellows, oranges, and reds in a complementary col- lage. After your summer and fall visits to spy on these trees you will probably have noticed the curious, interesting bark. Some might say that I have saved the best for last. The bark of S. pseudocamellia embodies the best of those bark characters attributed to London plane, crape-myrtle, parrotia, and lacebark pine, Pinus bungeana. It is varicolored and mottled in colors of cin- namon, buff, gray, and gray/plum. With this attribute, deciduousness becomes an asset. Stewartia pseudocamellia develops a py- ramidal, fastidious habit and may be a sin- gle- or multiple-stemmed tree. The ascen- dant branches show a slight zig-zag pattern from leaf bud to leaf bud. The most attrac- tive trees in the Arboretum are sited in part sun with shaded roots. They are tolerant of full sun, but the bark often becomes corky and less attractive under these conditions. Plant them in a moisture-retentive but well- drained acid soil. Summer irrigation should be applied until the tree is established and during prolonged summer drought. Jap- anese stewartia is perfectly hardy west of the Cascades and has withstood -25 de- grees F in the Midwest. Stewartia can be propagated by seed, which has a double dormancy and must be treated immediately upon collection in the fall. Seed germina- tion is not uniform. Cuttings root fairly easily if taken in late June or early July. Overwin- tering is a problem and cuttings should not be transplanted after rooting but hardened off, overwintered, and transplanted after new growth begins. Refer to The Reference Manual of Woody Plant Propagation by Michael A. Dirr and Charles W. Heuser, Jr., for more information. This useful text can be consulted in the Miller Horticultural Li- brary at the Center for Urban Horticulture. Stewartia pseudocamellia should not be crowded by other trees and large shrubs so that it can be fully appreciated. As men- tioned above, it thrives in high, filtered shade or partial sun. It would make a spec- tacular patio tree or specimen if under- planted with white-, chartreuse-, blue-, and pink-flowered, shade-loving perennials, such as astilbes, iris, and hostas. Low, shade-tolerant conifers, such as Taxus bac- cata ‘Repandens’, provide a pleasant, fine- textured companion for stewartia. Can I still challenge you? Stewartia pseudocamellia is, I think you will agree, a superlative tree for both residential and commercial landscapes. Several handsome specimens of this and other Stewartia spe- cies can be seen in the camellia section of the Washington Park Arboretum. I dare you to be disappointed? Herbicides and Water Pollution George Pinyuh Cooperative Extension Washington State University Whether an herbicide has the potential to find its way into ground or surface waters is dependent on a number of factors: (1) sol- ubility, whether the chemical readily dis- solves in water; (2) adsorption, how tightly it can bind to clay and humus particles in the soil; and (3) degradation, how fast soil mi- crobes or other factors break it down into harmless components. All these factors will influence a chemical’s movement in the soil. External factors that must also be consid- ered are soil texture, the slope of the land on which an herbicide is used, and how close to the soil surface ground water might be located. Hardpans or other impermeable subsoil layers may also influence the move- ment of an herbicide in the soil. Texture refers to the amount of sand, silt, or clay that make up a soil. Soils that contain a fair amount of clay are less likely to allow rapid movement of herbicides down through them. The clay particles tend to bind the herbicide molecules tightly to themselves, thus reducing the likelihood of leaching into the ground water. A soil con- taining humus will act in much the same way, binding the chemicals. Erosion or sur- face runoff may, however, carry the parti- cles of clay along with their tightly adsorbed herbicides into surface water. Sandy soils do not adsorb chemicals, and rapid movement through them is more likely. An herbicide that is very soluble in water may therefore be carried right down through the profile and wind up in the ground water relatively quickly; however, incorporating plenty of organic matter or humus into a sandy soil will help bind up the herbicides. Many chemicals are attacked and broken down by microbes in the soil. Those that are degraded quickly will have less of a chance to contaminate water supplies. In addition, some herbicides are broken down fairly rapidly through a process called pho- todecomposition, and these, too, will be less likely to find their way into ground- water. What is the water-pollution potential for some of the commonly used herbicides? Casoron is a preemergent herbicide that has fairly long residual activity — from six to eight months; however, it is not very soluble in water, and it is adsorbed to clay and organic matter in the soil. If not overapplied, it should not be a problem. Glyphosate (the active ingredient in Roundup, Kleenup, and Knock-Out) is not likely to move in the soil because it has a high binding potential. So even though it is highly soluble in water, it is not a potential problem. Glyphosate is broken down by microbes in about two months. 2,4-D, used to kill lawn weeds, does not last very long in the soil, only from one to four weeks. Because it is quite soluble, though, it may leach through very sandy soils. If used at the recommended rates and frequencies, it should not be a problem. MCPP and dicamba (Banvel) are also used frequently to deal with broadleaf weeds in lawns. At the rates they are used in lawn weedkiller formulations, they should be safe. However, they are quite soluble and could contaminate ground water if overap- plied. Fluazifop (Grass-B-Gon) and sethoxydim (Poast) are a couple of herbicides that are effective in killing grass weeds growing among broadleaf plants. Because their sol- ubility is very low, and since they are not active for long, neither of them should pre- sent any ground-water problems. Prometon, a chemical included in a number of soil sterilants like Triox and Noxall Con- centrate, can be active for a long time in the soil, up to three years. It is extremely solu- ble, does not bind tightly in the soil, and may be a potential problem. Other soil sterilants like the chlorates and borates are very soluble, last up to a year in the soil as active materials, do not tightly bind to the soil, and are not broken down by microbial activity. In western Washington they are very subject to leaching and there- fore are a potential problem. Balanced Plant Development — An Opinion Dr. Barbara Smit Center for Urban Horticulture University of Washington Land plants are faced with a remarkable challenge. Not only are they stationary or- ganisms, unable to move around to seek resources and avoid biotic and environ- mental stresses, but they also must cope with two distinctly different environments, above and below ground. To be successful, plants must acquire the resources they need. From the soil they get water and nu- trients. Above ground, they must capture light energy to fix C02 into sugar, from which all of the organic constituents of plants are derived. The plant must balance its resource acquisi- tion. Without adequate supplies of any one resource, the plant cannot effectively use or acquire the others. For example, if a plant is unable to absorb and transport enough water to sustain a high leaf-water content, the stomates will close, reducing photo- synthesis and growth. If photosynthesis is limited by inadequate light interception due to insufficient shoot growth, root develop- ment will be restricted by limited supplies of organic molecules. Hence, the ability of the roots and shoots to supply each other with necessary resources relies on a balance be- tween the two parts of the plant. The nature of this balance is not static but depends on the environmental conditions below and above ground. There are several examples to illustrate the dynamics of sup- ply and demand. In a sunny location, plants need less leaf area than in a shady site to be able to maintain a level of photosynthesis. In a nutrient-poor soil, plants must develop a large root system to supply the shoot with the same level of nutrients available from a smaller root system in a fertile soil. Likewise, Registration Form: Landscape Maintenance Seminars Preregistration Rates (At least one week in advance) Complete Series: Perennials, Xeriscaping, Drip Irrigation, Water Quality $70.00 Water Conservation Seminars: Xeriscaping + Drip Irrigation $50.00 Perennials $12.50 Xeriscaping $35.00 Drip Irrigation $35.00 Water Quality $12.50 TOTAL: $ Group Rates: Firms/institutions sending two or more employees per seminar will receive the following discounts: 2-5 employees: 20% off single seminar rates 6 or more employees: 30% off single seminar rates To qualify for group rates: (1) firm’s registration must be received at least one week in advance; (2) all registrants must be from same firm; (3) total registration fee must be paid with one check or money order. Firms using purchase orders must make prior registration arrangements. Make checks payable to the University of Washington; no bank cards. Portion of fees may cover refreshments and speakers’ expenses. Receipts will not be returned by mail; they will be available at the door. NAME ADDRESS CITY STATE ZIP PHONE (day) (evening) Mail payment and registration form to: Urban Horticulture Program, University of Washington, GF-15, Seattle, WA 98195. For more information please call (206) 545 — 8033. development of a large root system requires a great deal of fixed carbon, and a large leaf area requires a high input of nutrients. Therefore, a plant growing in a given loca- tion must attain a balance between growth and resource acquisition appropriate to that site. What does this mean for plant growers and landscape managers? To enhance the prob- ability that a plant will succeed in a given site, one should encourage a pattern of plant development appropriate for that site. If, for example, a plant will be in a low- maintenance site with periodic droughts and low fertility, installing a plant that has been grown under lush conditions will set the plant up for failure. It is likely to have an inadequate root system relative to the size of the shoot. Likewise, adding a one-time shot of fertilizer to a site may encourage top growth at the expense of root growth during the first growing season or two, resulting in a plant poorly suited to its long-term environ- ment. Research Digest Van Bobbitt Center for Urban Horticulture University of Washington • Susceptiblity to Spruce Aphid American species of spruce appear to be much more susceptible to spruce-aphid in- festation than Asian species, according to field and laboratory observations at a Brit- ish forestry research station. In the field all the American species, except one, supported large populations of spruce aphid. But the following 6 Asian, 2 Eura- sian, and 1 American species were aphid- free: P brachytyla, P. glehnii, P. koyamai, P. polita, P. schrenkiana, P. jezoensis, P omorika, P. orientalis, and P. rubens. In laboratory tests, the aphids showed greater growth rates while feeding on the American species, than while feeding on the Asian species. Of the Eurasian species, aphids achieved rather high growth rates on P. abies but low growth rates on P orientalis and P omorika. Nichols, J.F.A. 1987. Damage and per- formance of the green aphid, Elatobium abietinum, on twenty spruce species. Ento- mol. Exp. Appl. 45:211-217. • Transplanting Practices: Pruning, Antitranspirants, and Growth Reg- ulators Researchers at Cornell University evaluated the effects of dormant pruning, a film anti- transpirant, and a growth regulator (paclobutrazol) as transplanting treatments on young ‘Colt’ cherry trees. Under water- stressed conditions, all three treatments re- duced water stress in the plants; the pruning and antitranspirant also resulted in im- proved growth rates. With irrigation, how- ever, these treatments were not beneficial and significantly reduced growth. The re- searchers feel that “there is little justification for dormant pruning, use of anti- transpirants, or application of paclobutrazol when transplanting stock if the plants are to be well irrigated. ” Ranney, T.G., N.L. Bassuk, and T.H. Whitlow. 1989. Effect of transplanting prac- tices on growth and water relations of ‘Colt’ cherry trees during reestablishment. J. En- viron. Hort. 7(l):41-45. CENTER FOR URBAN HORTICULTURE University of Washington, GF-15 Seattle, WA 98195 Nonprofit Org. U.S. Postage Paid Permit No. 62 Seattle, WA Center tor Urban Horticulture 3501 NE 4ist Street University of Washington GF- 15 Seattle Washington 98195 206 545-8033 SUMMER 1989