g(.k\ i<&pi mm PROHORT Vol. 9, No. 3 Summer 1991 PROHORT seminars for the landscape professional are planned and conducted cooperatively by Urban Horticulture, University of Washington and Washington State University Cooperative Extension Service. Edmonds Community College and South Seattle Community College also assist cooperatively. LOW WATER USE PLANTS FOR THE NORTHWEST DATE: Wednesday, July 1 7 TIME: 8:30 a.m. to 12:30 p.m. LOCATION: Center for Urban Horticulture INSTRUCTORS: Dan Hinkley, Dr. Art Kruckeberg, Dan Borroff FEE: $20 Selecting the right plant for the right place is the first step to lowering main- tenance needs. Plants that can tolerate oursummerdrought periods with little or no supplemental irrigation will lower water and labor costs and thus are alternatives worth considering. FIELD DIAGNOSIS: A Systematic Approach to Diagnosing Plant Damage DATE: Wednesday, August 14 TIME: 9 a.m. to 3:30 p.m. LOCATION : Graham Visitors Center, Washington Park Arboretum INSTRUCTOR: Dr. James Green, Ex- tension Horticulturist, Oregon State University FEE: $32, lunch included PRE-REGISTRATION IS REQUIRED, REGISTRATION IS LIMITED This course earns 6 hours WSDA pes- ticide recertification credit. HAZARD TREE EVALUATION DATE: Friday, September 13 TIME: 9 a.m. to 3 p.m. LOCATION: Graham Visitors Center, Washington Park Arboretum INSTRUCTORS: Nelda Matheny, Hort Science Incorporated, Pleasanton, CA; Chris Pfeiffer, Horticulturist, Washing- ton Park Arboretum FEE: $28, lunch included PRE-REGISTRATION IS REQUIRED, REGISTRATION IS LIMITED. This seminar is being repeated to accomodate earlier demands. I. Trees and Shrubs Dan Hinkley, Heronswood Nursery and Instructor at EdmondsCommunity College, leads this review of trees and shrubs worthy of use in our landscapes yet tough enough to survive summer drought. II. Choice Natives I. Lecture Effective treatment of plant problems requires accurate diagnosis. The prob- ability of correct diagnosis based on only a few clues is low, but through the systematic process of deduction and elimination outlined in this presenta- tion the most probable cause of dam- age can be determined. I. Evaluation Principles Learn the principles of tree evaluation relative to tree health and location from expert Nelda Matheny. Become familiar with the latest evaluation worksheets. II. Evaluation Demonstrations University of Washington Professor Emeritus Art Kruckeberg discusses some of the attractive native plants that could be used more frequently in Northwest landscapes. III. Other Plants and Issues Landscape Designer Dan Borroff ad- dresses design considerations for cre- ating drought tolerant landscapes, and reviews assorted perennials and other plants to consider for this region. II. Field Practice Using the Arboretum as a living labo- ratory, we will practice diagnosis with this systematic approach. Sharon Collman, WSU Liason to EPA, and George Pinyuh, WSU Extension Agent, will join Dr. Green to serve as facilita- tors for this practical field experience. Registration information See page 3 Field evaluation demonstrations and discussions focusing on factors spe- cific to various tree groups. Nelda Matheny and Chris Pfeiffer lead this orientation to field work. Ell. Participant Practice Evaluations Attendees get their chance to practice tree evaluation skills on Arboretum specimens. Following this indepen- dent field work, evaluations will be reviewed by instructors. OTHER EDUCATIONAL RESOURCES New Urban Forestry Curriculum A new Urban Forestry undergraduate curriculum is now being offered at the University of Washington. This field of study is based in both forestry and horticulture and emphasizes both bio- logical and social processes. The cur- riculum focuses on threeareasof study: Plant Science (plant growth, responses to biotic and abiotic stresses, ecology); Planning and Management (design, management, administration of urban forest landscapes); and Social Processes and Institutions (interactions of plants and people in contexts of government, politics, and land-use policy). This curriculum also draws on offerings in fields such as botany, landscape archi- tecture, social sciences, environmen- tal studies, public administration, and urban planning. For more information on this degree program, contact Dr. Harold B. Tukey, Jr., Center for Urban Horticulture, U. of Washington, GF- 15, Seattle, WA 98195, or telephone (206) 543-8616. New Graduate Specialty The Center for Urban Horticulture at the University of Washington is offer- ing a new graduate specialty in Botani- cal Garden Management and Public Horticulture leading to the Master's degree. This MFR-Urban Horticulture degree provides a secure background in plant science, superior knowledge of Northwest plant materials, and prac- tical experience from an internship emphasizing some aspect of public horticulture. For more information, contact Dr. Harold B. Tukey, Jr., at the address listed above. Plant Palette Lecture Oaks July 20, 9 to 1 1 a.m. Graham Visitors Center, Washington Park Arboretum $5, payable at the door Curator Tim Hohn leads this lecture and field examination of the Arboretum's Quercus collection. Ap- propriate and unusual selections for landscape use will be discussed. Summer Nursery Tour: Wet Foot Wonders Saturday, July 27, 9 a.m. to 4 p.m. $29, pre-registration required Tour one nursery specializing in aquatic ornamentals and another nurs- ery offering native wetland plants. Then, visit a restored wetland site where CUH's Dr. Kern Ewing leads a first- hand look at how these unique plants grow and are utilized. Edmonds Community College Sum- mer Courses: Horticultural Design, Greenhouse Studies, Advanced Prun- ing & Renovation, Bidding & Estimat- ing. ECC Fall Courses: Horticultural Tools& Equipment, Fall Plant ID, Land- scape Design I, Horticultural Design, Landscape Materials, Landscape Reno- vation, Plant Insects, Creative Flower Arranging, Ornamental Grasses, Land- scape Business. Call 771-1679 for registration information. South Seattle Community College Fall Courses: Plant ID, Greenhouse Op- erations, Small Business Management, Landscape Design I & III, Advanced Plant ID, Maintenance Estimating & Bidding, Landscape Construction & Design, Weed ID. RESEARCH REVIEW By Dave Stockdale The effectiveness of hydrogels (water- absorbing polymers) continues to be refuted. Hydrogels can absorb many times their weight in water and there- fore have been thought to reduce wa- tering requirements of container grown plants. However, researchers at the Alabama Agricultural Experiment Sta- To reprint material from this pub- lication, obtain permission from the editor and cite ProHort. PROHORT Editorial Staff: Dave Stockdale, Coordinator George J. Pinyuh, County Extension Agent, Horticulture John A. Wott, Associate Director, CUH tion of Auburn University have re- cently documented that irrigation fre- quency was not reduced using hydrogels. They also reported that plant growth was either unaffected, or in some cases suppressed, when using hydrogels. Furthermore, the water absorbency of hydrogels is greatly reduced in the presence of free cations released from irrigation water or soil amendments such as gypsum and Osmocote 1 8-6- 12. After three years of testing in amended soils, researchers were un- able to duplicate any of the beneficial effects of hydrogels (except for water holding capacity) suggested by some manufacturers. Consider these recent results and try similar tests before de- ciding if or where to use hydrogels in yourbusiness. Foster, W.J., and Keever, G.J. Water absorption of Hydrophylic Polymers (Hydrogels) Reduced by Media Amendments. J. Environ. Hort 8(3) : 1 1 3-1 14. September, 1990. Keever, G.J., Cobb, G.S., Stephenson, J.C., and W.J. Foster. Effect of Hydrophlic Polymer Amendment on Growth of Container Grown Land- scape Plants. J. Environ. Hort. 7(2) :52- 56. June, 1989. PROHORT BOOKSHELF by Valerie Easton Horticultural Librarian New books of interest to professionals now available in the Miller Library. Please note: the library will initiate a lending collection this summer. Call 685-8033 for details. Ettlinger, Steve; Coleman, Robert S. The Complete Illustrated Guide to Ev- erything Sold in Garden Centers (Ex- cept the Plants). New York: Macmillan, 1990. Hannebaum, Leroy. Landscape De- sign: A Practical Approach. 2nd ed. Englewood Cliffs, NJ: Prentice Hall, 1990. Hoefer, Philip J.; DeVoto, David F.; Himelick, E.B. Municipal Tree Manual. Urbana, IL: International society of Arboriculture, 1990. FUNCTIONS OF WETLAND SOILS Ai^l Date & Time: Tuesday, December 10, 9:30 a.m. Location: Center for Urban Horticulture Fee: $45, fee includes lunch OR 1^1 to 4:30 p.m. P<1) 4 a Date & Time: Monday, December 9, 10 a.m. to 5 p.m. ft ^ cl jc Location: Bellingham Voc Tech Institute, Bellingham Fee: $45, fee includes lunch (Seating capacity is limited to 60 persons for this program) Pre-registration required- Use form below BASICS OF WETLAND SOILS Dr. Rob Harrison, Assistant Professor, University of Washington Review of wetland soils composition, structure, and chemistry , including a discussion of the sequence of events that has led to the formation of our Washington wetlands. WATER RELATIONS Dr. Terry Cundy, Associate Professor, University of Washington Discussion of seasonal water dynamics and water relations in wetland soils. HEAVY METALS Dr. Kel Wieder, Professor, Villanova University J\€VWW OI 1&L&&L 1 Udcct Oil SUO Y Ci/iwij C ciiiti ksa. r iiiwtuiu lii wetland soils SOIL RELATIONS Sarah Cooke, Pentec Environmental, Inc. Discussion of the relations between soils, wetland soils development, and vegetation establishment and growth. REGISTRATION FOR FUNCTIONS OF WETLAND SOILS (# of people) December 10, Center for Urban Horticulture $45 December 9, Bellingham Voc Tech Institute $45 TOTAL $ Name of persons attending/Company Name Address City State Zip Daytime Phone Make checks payable to University of Washington and mail to: Center for Urban Horticulture, University of Washington, GF-15, Seattle WA 98195. For information, call 685-8033. Portion of fees may cover refreshments and speaker expenses. 29 ON JLIIfllUad ysBM 'WB9S a i vd aovisod s n OHO HHOHdNON S6186 VM '^IWeas ajn)|roujoH ueqjpi joj jaiua;} saajnosay jsajoj jo aSa||CQ S l~dD 'uojSuiqsB/v\ 10 AiisjaAjun Langhans, Robert W. Greenhouse Management: A Guide to Structures, Environmental Control, Materials Han- dling, Crop Programming, and Busi- ness Analysis. 3rd ed. Ithaca, NY: Halycon Press, 1 990. Oregon State University, Washington State University, University of Idaho. Pacific Northwest Insect Control Hand- book, 1991, Oregon State University, Washington State University, University of Idaho. Pacific Northwest Plant Disease Con- trol Handbook, 1991 . Oregon State University, Washington State University, University of Idaho. Pacific Northwest Weed Control Hand- book, 1991. Parnes, Robert. Fertile Soil: A Grower's Guide to Organic and Inorganic Fertil- izers. 2nd ed. Davis, CA: agAccess, 1990. Rancho Santa Ana Botanic Garden. Drought Tolerant Planting Bibliogra- phy. Technical Report #6, June 1 990. Shigo, Alex L. Modern Arboriculture: A Systems Approach to Practical Tree Care. Durham, NH: Shigo and Trees, Associates, 1991. RESEARCH REPORT Research at CUH: Growing Trees in Restricted Rooting Zones By Dr. Barbara Smit In horticultural nurseries and land- scape sites, we often grow plants un- der unusual conditions that the plants would not encounter in their natural environment. One good example of unusual growing conditions is the prac- tice of growing plants in pots or other restricted rooting zones. In the Horti- cultural Physiology lab at the Center for Urban Horticulture, we have been studing the effects of growing trees in restricted rooting volumes. First, let's set the stage by picturing the tree as a resource-gathering and re- source-using organism. The above- ground portion (shoot) of the plant must gather light energy and carbon dioxide to make sugars. The sugars produced by the leaves provide the energy and basic raw materialsto build and maintain the entire plant includ- ing the roots. The below-ground por- tion (roots) of the plant must gather water and mineral nutrients for the plant shoot as well as anchor the plant in the ground. Obviously, forthe plant to function properly, the roots and shoots must be in balance relative to the availability of these resources. For example, in low light environments, plants tend to grow relatively more shoots than roots. In low nutrient, and low water environments, plants tend to produce relatively more roots than shoots. When we grow a plant in a pot or container, we limit the available space in which roots can grow. When the plant has filled the available rooting volume, the rate at which leaves grow is reduced. This results in smaller leaves and less total leaf area on the plant relative to plants in unrestricted soil volumes. This response occurs even if the plant is provided with abun- dant water and nutrients in the pot. A striking example of this phenomenon are plants in bonsai culture. In bonsai, root pruning and restricted volumes are used to produce miniature plants. Similarly, many plants grown in con- tainers or limited volume beds in the nursery and in landscapes sites, will grow less even with good maintenance. If there are adequate water and nutri- ents provided, how does the plant “know" that it's roots are restricted and "tell" the shoot to slow growth? We are exploring two possibilities. First, the plant may produce plant growth regulators in actively growing root tips and send the growth regulators to leaves to stimulate growth. When rootgrowth is restricted, the leaves no longer re- ceive as much of the growth stimulat- ing compound. Second, the leaves store starch during the day, which they break down and send to the roots as sugar during the night for growth. When root growth is restricted, starch accumulates in the leaves. Perhaps the leaves can "sense" starch levels and subsequently slow their growth. For the horticulturist, is this response good or bad? It may depend on your objectives. If you are trying to grow a tree rapidly for sale, root restriction can slow growth regardless of your other cultural practices. Likewise, if you are interested in maintaining a large-leaf texture, root restriction will cause reduced leaf sizes. On the other hand, if you are interested in having small plants, root restriction will natu- rally slow plant growth and help with survival since it will help keep the need for water and nutrients in line with root system size. To date, we do not know of any other adverse effects of limited rooting volume on the physi- ology of the plant. PROHORT Seminar Registration Low Water Use Plants $20.00 Field Diagnosis $32.00 Hazard Tree Evaluation $28.00 TOTAL : $ Group rates: 2 — 5 persons, less 20%; 6 or more, less 25%. Group registrations must be accompanied by ONE check or purchase order, at least one week in advance. Portion of fees may cover refreshments and speaker expense. Make checks payable to the University of Washington; receipts available at the door. Mail payment and registration to: Center for Urban Horticulture/ProHort, University of Washington, GF-15, Seattle, WA 98195. For information, call 685-8033. Company Name Address City State Zip Day Phone Evening Phone m PLANT PROFILE Quercus myrsinifolia and Quercus nubium by Timothy Hohn Japanese gardeners have cultivated evergreen oaks in the landscape for centuries and magnificent, ancient specimens can be seen in parks and on temple grounds. During the last few centuries, many selections of ever- green oaks with crisped, laciniate, and variegated foliage have been made. Unfortunately, few, if any, of these selections have been imported to the United States. To our greater shame, Asian evergreens oaks, some of which are quite hardy, are virtually unknown in American horticulture. The two Arboretum accessions in the Japanese Garden are particularly worthy of our attention. Quercus myrsinifolia and Q. nubium are well sited in the northwest corner of the Japanese Garden. Both of these trees have developed into tidy, round- headed specimens under the astute care of the garden staff. Neither be- comes the massive tree we we ordi- narily associate with oaks, and there- fore, they are quite well suited to urban sites and small residential properties. Their small, but stately, stature; hand- some evergreen foliage; and tawny, golden new growth make them very desirable landscape specimens. Quercus nubium did survive the re- cent winter cold spells, but there was significant leaf burn. Quercus myrsinifolia is found in Ja- pan, Korea, and the southwestern prov- inces of China . Its leaves are some- what more refined than those of other evergreen oaks, being less coracious and having a tapering tip studded with small teeth near the apex, for which it is greatly prized. In the wild it may reach 60 feet, but it is much more reserved in gardens and would be con- sidered large at 30 feet. This species is reported as bei ng one of the hard iest of all the evergreen oaks. Several selec- tions of this species exist in Japan with white and yellow variegation and vari- ous types of crisped foliage. Quercus nubium is a beautiful tree of exquisite form and foliage. The leaves are very thick and lanceolate/ovate in shape with an entire margin and a dark, nearly blue-green color. The spreading slender outline of the branches belies an elegance some- what out of character for an oak. At 20' tall and as much wide, the tree in the Japanese garden is nearly full size. Both of these special, yet uncharacter- istic, oaks would make attractive shade trees for small properties. They also should be considered in the Puget Sound Basin as potential street trees for narrowtree lawnsand low clearances. They should thrive in well-drained soils if planted in full sun. Supplemental* irrigation in summer is preferred, al- though not required once they are established. This is in contrast to Cali- fornia evergreen or live oak?, which should not be watered. Nurserymen interested in propagation material should contact Barbara Selemon, Propagator, Center for Ur- ban Horticulture GF-1 5, University of Washington, Seattle, WA, 98195. University of Washington, GF-15 College of Forest Resources Center for Urban Horticulture Seattle, WA 98195 Summer 1991 NONPROFIT ORG. U.S. POSTAGE PAID Seattle, Wash. PERMIT NO. 62