INTERIOR HORT. • • for interiorscape professionals Center for Urban Horticulture University of Washington Vol. 1, No. 2 Cooperative Extension Washington State University Autumn 1987 INTERIORSCAPE SEMINAR: Diagnosis and Treatment of Interior Plant Problems Date Time Location Instructor Tuesday, October 20 7 to 9 p.m. Center for Urban Horticulture Dirk W. Muntean Discover the step-by-step process profes- sionals use to diagnose interior plant mal- adies. Learn to properly treat prevalent in- sect, disease, and physiological disorders. Mr. Muntean is staff horticultural consultant for Soil and Plant Laboratory, Inc. of Belle- vue. He has a M.A. in physiological plant ecology from the University of California. This seminar qualifies for two hours of W.S.DA. pesticide license recertification credit. Registration Form: Interiorscape Seminar Registration Fee $10.00 Group Rates: Rates for firms/institutions sending two or more employees per seminar: 2-5 employees $8/person 6 or more employees $7. 25/person To qualify for group rates: (1) firm’s registration must be received at least one week in advance; (2) all registrants must be from the same firm; and (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 be used for refreshments and hosting speakers. Receipts will not be returned by mail; they will be available at the door. NAME ADDRESS CITY STATE ZIP PHONE (DAY) PHONE (EVE) Mail payment and registration to: Urban Horticulture Program, University of Wash- ington, GF-15, Seattle, WA 98195 For more information please call 545-8033. Miller Library — A Resource for Interiorscapers The Elisabeth C. Miller Library at the Cen- ter for Urban Horticulture has much to offer the interior landscape professional, such as trade journals (Interiorscape, Greenhouse Manager, Greenhouse Grower ), research journals (HortScience and Journal of En- vironmental Horticulture often carry inte- rior plant research reports), a set of Wash- ington State University extension bulletins, and pest control references. Books of spe- cific interest to interiorscapers include: Interior Plantscaping, Richard Gaines; Commercial Indoor Plants and The Art of High-Tech Watering, David L. Hamilton; The Encyclopedia Botanica — The Defini- tive Guide to Indoor Blossoming and Fo- liage Plants, Dennis A. Brown; Exotica Third, A.B. Graf; and Interior Plant- scapes — Installation, Maintenance, and Management, George H. Manaker. This noncirculating library is open to the public Monday through Friday, 9 a.m. to 5 p.m. Call 543-8616 for more information. INTERIOR HORT Editorial Staff: Dr. John A. Wott George J. Pinyuh Van M. Bobbitt, editor Indoor Outdoor Plants George Pinyuh Cooperative Extension Washington State University Research on the potential of temperate zone plants for interior environments has produced some interesting and useful re- sults over the past ten years. Many tested plants were found suitable for short term use indoors. They adapted to the lack of winter dormancy, put on new growth, and responded as if nothing was amiss when kept inside for up to nine months. Data reported in 1978 indicated that Camellia japonica and Magnolia grandiflora could survive and sustain quality in an interior landscape for ten years. Because temperate zone plants are adapted to winter cold, many of these species may tolerate the cold, drafty conditions fre- quently encountered in the winter near the entrances to shopping malls. Tropical plants in such situations often seem to be in a state of decline and look unattractive. Like most tropical species grown indoors, temperate plants usually benefit from ac- climation to low light intensity. Recent ex- periments at the Alabama Agricultural Ex- periment Station showed that a number of temperate zone species performed well in- doors when produced under substantial shade, but performance generally de- creased when the same plants were pro- duced under high light levels. Temperate plants grown outdoors under 64% shade performed well when placed indoors at 70°F. under 50 foot candles of fluorescent light for twelve hours each day. Researchers rated these plants on growth habit (density), leaf spacing, leaf drop, fo- liage color, and overall appearance over a 15 week period. After this data collection period, the plants were maintained under the same light and temperature conditions and fertilized every six weeks with Peters 20-20-20 for an additional five months. These plants resumed growth without ex- posure to low temperatures and short days, indicating that a period of dormancy is not necessary for all temperate zone plants. The following plants show potential value in the interior landscape. Other temperate zone plants may also acclimate to interior conditions, and further testing is certainly needed. Ajuga reptans Buxus microphylla Camellia japonica C leg era japonica Euonymus japonica Aureo-marginata’ Fatsia japonica Ficus pumila Gardenia jasminoides ‘Radicans’ Illicium anisatum Ligustrum japonicum ‘Variegatum’ Liriope muscari Magnolia grandiflora Mahonia bealei Mahonia fortunei Nandina domestica Ophiopogon japonicus Pittosporum tobira ‘Variegata’ Pittosporum tobira ‘Wheeler’s Dwarf Podocarpus macrophyllus var. maki Vinca minor Container Shape Affects Soil Moisture Van Bobbitt Center for Urban Horticulture University of Washington The soil water content in planters decreases with an increase in soil height. Therefore, the shape of a container greatly influences the soil moisture level. Soil in a wide, shal- low pot will retain more water after irrigation than that in a narrow, upright pot with an equal volume of soil. The effect of container shape on soil water content can easily be demonstrated by an exercise described by Dr. Art Spomer of the University of Illinois: A single, new cellulose sponge, a con- tainer of water, and any flat, level sup- port (e.g. a screen or sieve to allow free drainage) are required. The sponge has a small finite size, is relatively shal- low, and is open to the atmosphere at its top and bottom (drainage) surfaces and is therefore analogous to a con- tainer soil. Lay the sponge “flat” (Fig. 1-A) and pour water onto it until it is saturated and water drains freely through it. After drainage ceases (3-4 minutes), stand it up on its “side” (Fig. 1-B) and observe that more drainage occurs. After drainage ceases the sec- ond time (4-5 minutes), stand the sponge up “on end” (Fig. 1-C) and observe that still more drainage occurs. The sponge’s volume remains con- stant but its average water content de- creases (indicated by renewed drain- age) as the average height increases. In other words, a shallower container soil will be wetter than a deeper container soil. Though shallow plant containers are often considered more aesthetically pleasing than deeper containers, they may adversely af- fect the plants growing in them because: va=vb=vc 1) shallow pots will have a greater volume of saturated soil immediately after irrigation; 2) soils in shallow pots also tend to dry out faster because more soil surface is exposed to the atmosphere; 3) effective irrigation scheduling is trickier in shallow pots than in deeper pots. Reference: Spomer, L. Art. 1974. Two classroom exercises demonstrating the pat- tern of container soil water distribution. HortScience 9: 152-153. hta dt> * d( h*a t * | .. v o " * ht. B * • K * • , % • • // t * y • t * <' Fig. 1. Exercise using sponge analog to demonstrate the relationship between a free-draining container soil average water content ( 0) and average height (ht). A. Sponge flat, maximum 0, minimum ht. B. Sponge turned on its side; lesser 0, (renewed drainage), greater ht. C. Sponge on end; minimum 0 (second renewed drainage), maximum ht. Since the volume (V) remains constant, the average 0 decreases as average ht. increases.