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Sven E. Svenson

Shoot and root growth responses of `Cunningham's White' rhododendron (Rhododendron x) was studied when grown in black plastic or molded fiber pots treated with copper hydroxide, or not treated. Containers of two sizes were studied, and the influence of pot type on substrate temperature was recorded. Rhododendron shoot height and dry weight was not influenced by pot volume, pot type, or copper treatment at 49, 131, or 362 d after potting. Rhododendron shoots were larger when grown in 3.8-L (trade 2-gal) pots compared to 2.8-L (trade 1-gal) pots, or when grown in 3.8-L fiber pots compared to 3.8-L plastic pots, both 131 and 362 d after potting. Copper treatment did not influence shoot size. Copper treatment reduced the amount of circling or matted roots at the container-substrate interface for both plastic and fiber pots, but there was better control of root growth in 3.8-L pots compared to 2.8-L pots. Substrate average minimum temperatures were warmer, and average maximum temperatures were cooler when pots were located near the center of the growing block compared to the southwest corner ofthe growing block. Substrate average maximum temperatures were cooler in fiber pots compared to plastic pots, but only when pots were located on the southwest corner of the growing block.

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Bonnie L. Appleton and Susan C. French

A commercially available copper-treated disk was evaluated for its effect on weed suppression for container-grown willow oak (Quercus phellos L.). No weeds grew in containers where disks were used. All trees grown without disks or preemergent herbicide were dead within 6 months. Top dry weights were greater for trees grown with disks or preemergence herbicide, but root dry weights were not different.

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S.L. File, P.A. Knight, C.G. Gilliam, D.B. Reynolds and R.L. Harkess

Non-target herbicide losses pose environmental concerns for nurseries. Therefore, the objective of this research was to determine the ability of each alternative mulch to suppress weed growth when compared to traditional chemical methods. Uniform quart liners of Lagersroemia indica × faurei `Natchez' were planted in 15-gal containers 15 June 1999, on a gravel container pad using overhead irrigation. Weed pressure was uniform. Treatments include Regal 0-0 3 G (3 lb ai/a) as a broadcast or individual container application, recycled newspaper pellets (1 inch thick), Spin-out coated recycled newspaper pellets (1 inch thick) geotextile disks (Spin-out coated), kenaf mulch, waste tire crumbles, wheat straw (2 inches thick), oat straw (2 inches thick), cereal rye straw (2 inches thick), paper mill sludge (2 inches thick), a handweeded control, and a weedy control. Treatments were organized in a RCBD consisting of eight single-plant replicates. The geotextile disks, newspaper pellets treated with spin-out, and shredded rubber tire treatments all had better than 80% weed control from 30 to 180 DAT. These alternative weed control methods can provide a good alternative to conventional weed control practices in large container-grown ornamental.

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Larry J. Kuhns, Tracey Harpster and Clyde Elmore

SpinOut is a commercial product containing copper hydroxide that is designed to prevent the development of circling roots in container grown ornamentals. Our objective was to determine the effect of two root-inhibiting herbicides (oryzalin and trifluralin) on the development of circling roots in container grown ornamentals when painted onto the inside surface of the containers or on stakes inserted around the walls of the containers. Rooted cuttings of wintercreeper euonymus (Euonymus fortunei Hand.-Mezz) were planted in a 1 peat: 1 perlite: 1 soil mix on 8 to 10 Feb. 1995. There were 16 containers for each of 20 treatments. Eight were rated for circling roots then harvested 17 to 22 May, and eight were rated and harvested 6 to 7 July 1995. Root circling was rated on a scale of 1 to 5, with 1 indicating no circling roots and 5 indicating many circling roots. Following harvest stem growth was measured and the dry weights of the roots, stems, and leaves were determined. Treated stakes did not prevent circling roots Trifluralin in Vapor Gard reduced the amount of circling roots, but not to acceptable levels. Trifluralin in latex paint was ineffective at 0.5%, slightly reduced the development of circling roots at 2%, and at 4% reduced circling rooting to the same extent as the SpinOut. Surflan at 0.5% in Vapor Gard reduced the development of circling roots to the same extent as the SpinOut. All other rates of Surflan, in both carriers, almost totally eliminated circling roots. There were no significant differences in root weight or total plant weight among any of the treatments at either date of evaluation.

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Steven E. Newman and Jesse R. Quarrels

Many nurseries are using the pot-in-pot (PNP) system to grow trees in containers. This system protects the roots from temperature extremes and prevents tipping. PNP is not without problems, trees with vigorous roots may escape the container and root into the external soil making harvest difficult. PNP has no effect on root circling. Our objective was to determine if a polypropylene fabric disk treated with either trifluralin or copper placed in the bottom of a container would prevent root circling. Cercis canadensis and Quercus shumardii seedlings were grown in 19 liter polyethylene containers with eight root control treatments, which included trifluralin or copper impregnated polypropylene fabric disks placed in the bottom of the containers. Ttifluralin treatments, BioBarrier and trifluralin impregnated fabric, had few roots in the bottom of the containers. Of the copper treatments, Spinout® impregnated fabric was the only copper treatment that had any effect on root development in the bottom of the containers.

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Tom J. Buechel, Edward R. Hasselkus and Brent H. McCown

Root girdling and deformation are problems that occur in containerized woody ornamentals. Two small trees, the coarse-rooted Magnolia × loebneri `Leonard Messel' (grown in 5-gal containers), and the fine-rooted Crataegus × viridis `Winterking' (6' bare root), were transplanted into 10-gal containers, some of which were treated with “SpinOut” [a latex paint containing 100 g Cu(OH)2/liter]. The plants were grown in a pot-in-pot system for 3 months, after which new roots were analyzed for mat formation and branching pattern. No significant differences in shoot growth that could be attributed to the Cu(OH)2 treatment were observed. The treated containers prevented both root encirclement and reformation of matted roots, and resulted in a more-dense and fibrous root system than that observed in untreated containers. The differences were greatest with the coarse-rooted magnolia. The use of containers treated with copper compounds may be an effective means to reduce root problems commonly observed in modern containerized ornamental production.

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Desmond R. Layne and L.N. Peters

This experiment was designed to determine the optimal light level for growing pawpaw seedlings in the greenhouse. In addition, we wanted to determine if modifying the root-zone would positively impact pawpaw seedling growth and development. Experimental treatments were imposed from seed sowing until the plants were destructively harvested. The experimental design was a split-plot, where blocking was done by position in the greenhouse. The main plot of the experiment was shade. This was accomplished by growing seedlings under a wooden frame covered with shadecloth to reduce incident light intensity received by the plant by 30%, 55%, 80%, or 95%. The control treatment was 0% shade or ambient greenhouse light level. The split-plot was root-zone modification. Half of all growing containers were untreated (control) while the other half were painted with SpinOut™, a commercially available product used to reduce root spiraling in nursery containers. There were 40 replicate seedlings per experimental treatment combination per block. Seedling shoot length and unfolded leaf number was recorded twice a week from seedling emergence until destructive harvest. Whole-plant leaf area was also determined. Leaves, stems, and tap and lateral roots were separated and dried to determine biomass partitioned to the respective organs. Up to 55% shade did not significantly reduce whole-plant biomass, while plants at 80% and 95% shade were stunted. Shade in the greenhouse is not required as was previously thought. Specific leaf mass and lateral root mass decreased as shade increased. Neither tap or lateral root dry weights were significantly affected by root-zone modification. New recommendations for container production of pawpaws in the greenhouse will be discussed.

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Alison A. Stoven*, Hannah M. Mathers and Daniel K. Struve

A study was conducted to determine if similar quality shade tree liners could be produced using a retractable-roof greenhouse structure versus an outdoor environment. All plants were started in a heated greenhouse on campus in 250 XL-sized containers. The species included Eastern redbud, red oak (both grown from seed) and Autumn Blaze maple and Prairifire crabapple (both grown from rooted cuttings). On 15 Mar. 2003, half the plants remained in the heated greenhouse and the other half were moved to a Cravo retractable-roof structure and placed on heating mats set at 22 °C. In May, all of the plants (retractable and greenhouse) were upshifted into 3-gallon Spin-out® treated containers. Trees in each environment were fertilized with either Osmocote® (20 N, 2.2 P, 6.6 K), nine month release, applied broadcast at 45 g/pot, or with a 100 ppm-N water-soluable fertilizer (21 N, 3.1P, 5.9 K), applied at 0.1 g N/day. All trees received the same irrigation volume (1 L/day). All trees were grown according to nursery standards including bamboo staking, taping and regular pruning. Plants were arranged in a completely randomized design in each environment. The Cravo structure provided a more uniform environment with reduced air and soil temperature fluctuations versus the outdoor environment. Liners produced in the Cravo structure were taller, had greater caliper and root and shoot mass. Slow release fertilizer produced larger plants. Root dry weight for trees inside the Cravo environment increased nearly five times over the harvest dates of July to October with the maples having the largest root weight.

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Tongyin Li, Guihong Bi, Genhua Niu, Susmitha S. Nambuthiri, Robert L. Geneve, Xueni Wang, R. Thomas Fernandez, Youping Sun and Xiaojie Zhao

treated 18 × 18-inch fabric squares (Textel SpinOut; A.M. Leonard Co., Piqua, OH) were placed between each production and socket pot to prevent root escape from the production pot and rooting into the soil ( Ruter, 1994 ). The ground was covered with

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H.M. Mathers, S.B. Lowe, C. Scagel, D.K. Struve and L.T. Case

of pre-emergent herbicides are not uncommon to keep the “chemical barrier” on the container substrate surface, few studies have investigated the effects of these herbicides on root development of the crop in container production. Copper. Spinout