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  • Author or Editor: Janet C. Cole x
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Woody plant species were treated in 1995 and 1996 with 0, 1, 2, or 4 lb/acre (0, 1.1, 2.3, or 4.5 kg·ha-1) propazine (a.i.). Species studied in 1995 included rose-of-sharon (Hibiscus syriacus L. `Double Purple'), japanese boxwood (Buxus microphylla Sieb. & Zucc. `Green Mountain'), butterfly bush (Buddleia davidii var. Veitchiana Rehd. `Nanho Purple'), euonymus (Euonymus fortunei var. acutis Hand-Mazz. `Emerald n'Gold'), forsythia (Forsythia ×intermedia Zab. `Lynnwood Gold'), fire thorn (Pyracantha angustifolia Roem. `Gnome'), and japanese spiraea (Spiraea japonica L.f. `Goldflame'). Crape myrtle (Lagerstroemia indica L. `Acoma' and `Zuni') and juniper (Juniperus chinensis L. `Pfitzeriana') were added and euonymus and japanese spiraea were omitted in 1996. In both years, statistical analyses revealed differences in height and visual quality between plants exposed to propazine and control plants of some species; however, differences were inconsistent in that some plants treated with propazine were larger or rated better than control plants while other plants were smaller or of lower quality than their corresponding control plants. In all cases, differences among propazine treatments within each species were <1.2 inches (3 cm) in height while decreases in visual quality compared to control plants were most evident in plants receiving four times the recommended rate of propazine. The horticultural significance of these differences was, therefore, considered small, suggesting that all of the species tested are tolerant to propazine applied at the recommended rate of 1 lb/acre (1.1 kg·ha-1). Chemical names used: 6-chloro-N,N'-bis(1-methylethyl)-1,3,5-triazine-2,4-diamine (propazine).

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Vinca minor production in Oklahoma nurseries has declined in recent years due to foliar diseases. A study was conducted to determine whether several labeled and experimental fungicides control these foliar diseases in Vinca minor `Bowles'. This study was conducted outdoors under unusually mild and humid conditions, which were conducive factors for disease symptoms to occur throughout the season. Plants were sprayed at weekly intervals with the fungicides propiconazole (0.95 ml/liter), thiophanate methyl (1.58 ml/liter), thiophanate methyl/mancozeb (1.79 g/liter), triforine (3.95 ml/liter), CC 17461 (3.95 ml/liter), CGA 173506 (0.47/liter), or SAN 619 (0.79 ml/liter). Thiophanate methyl/mancozeb was the most effective of all chemicals at decreasing foliar dieback; however, no chemical completely controlled the disease symptoms throughout the season. Dry weights of plants treated with thiophanate methyl/mancozeb were greater at the end of the season than those of plants receiving the other fungicidal treatments.

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Summer and fall studies investigated the control of growth of bee balm (Monarda didyma ‘Marshall’s Delight’) by paclobutrazol, uniconazole, or flurprimidol applied to the substrate as a surface drench or through subirrigation. Flurprimidol and uniconazole were applied at 0, 0.5, 1.0, 1.5, or 2.0 ppm (0, 0.09, 0.18, 0.27, or 2.0 mg/pot), while paclobutrazol was applied at 0, 2, 4, 6, or 8 ppm (0, 0.6, 1.2, 1.8, or 2.4 mg/pot). Substrate drench applications were more effective than applications through subirrigation at reducing plant growth. Few trends in application concentrations within plant growth regulator occurred for the plant parameters measured. Based on inconsistent plant responses between the two studies and few differences among application concentrations, we do not recommend any of these plant growth regulators for controlling plant size of bee balm during production without further testing in production environments specific to bee balm.

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Five container substrates—3 pine bark (PB) : 1 peat (PT) : 1 sand (SD), 3 PB : 1 recycled paper (RP) : 1 SD, 2 PB : 2 RP : 1 SD, 3 vermiculite (VM) : 1 RP : 1 SD, and 2VM : 2 RP : 1 SD—were used to grow rose-of-sharon (Hibiscus syracus L. `Double Purple') and forsythia (Forsythia ×intermedia Zab. `Lynwood Gold') for 4.5 months. The control substrate (3 PB:1 PT:1 SD) had higher concentrations of NH4 * in leachate than other substrates at each of four sample times during the growing season except 4 Aug. Leaf number and leaf area per plant and height of rose-of-sharon were greater and the leaf area per leaf was smaller in all substrates containing recycled paper than in substrates without recycled paper. Forsythia plants had greater stem and root dry weights and were taller in substrata without recycled paper than plants in substrates with recycled paper. Processed recycled paper is a possible component for container nursery plant production, but further testing on a large number of species is needed before widespread implementation.

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These studies were conducted to determine the effect of 1) temperature on P leaching from a soilless medium amended with various P fertilizers, 2) water application volume on P leaching, and 3) various fertilizers on P leaching during production and growth of marigolds (Tagetes erecta L. `Hero Flame'). Increasing temperature linearly decreased leaching fraction; however, total P leached from the single (SSP) or triple (TSP) superphosphate-amended medium did not differ regardless of temperature. Despite a smaller leaching fraction at higher temperatures and no change in the total P leached, P was probably leached more readily at higher temperatures. More P was leached from the medium amended with uncoated monoammonium phosphate (UCP) than from the medium containing polymer-coated monoammonium phosphate (CTP) at all temperatures, and more P was leached from UCP-amended medium at lower temperatures than at higher temperatures. More P was leached from TSP- than from SSP-amended medium and from UCP- than from CTP-amended medium regardless of the water volume applied, but leachate P content increased linearly as water application volume increased for all fertilizers tested. Plant dry weights did not differ regardless of P source. Leachate electrical conductivity (EC) was lower with TSP than with SSP. Leachate EC was also lower with CTP than with UCP. A higher percentage of P from controlled release fertilizer was taken up by plants rather than being leached from the medium compared to P from uncoated fertilizers.

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Wet Earth (WE) is a recycled paper product that may substitute for peat moss as a growth substrate. WE is available at various pH levels and may be formulated using: 1) paper production byproducts (WES), or 2) recycled corrugated cardboard (WEC). Use of WE by commercial growers would reduce demand for both landfill space and for slowly renewable resources such as peat and pine bark. Experiment objectives included: analyzing plant performance of azaleas (Rhododendron obtusum `Hino Crimson') in WE-based growth substrates at pH 3.4 and pH 6.6 and in peat-based growth substrates (Trial pH), 2) analyzing plant performance of WES, WEC, and peat moss-based growth substrates (Trial SC), and 3) determining changes, if any, in substrate physical properties from planting to harvest. Shadehouse experiments were conducted in summer of 1996. Ratios of pine bark to WE tested were 100% pine bark, 1:3, 1:1, 3: l, and 100% WE by volume. Plant heights, widths, and visual quality ratings were obtained monthly throughout the 16-week experiment. Leaf, shoot, and root dry weights and leaf nitrogen concentration were determined at harvest. Changes in volume, bulk density, porosity, and air space were also measured. Plants performed poorly in WES, pH 3.4, with mortality exceeding 90%. Peat and WEC yielded similar (and best) results. Optimum plant performance for all substrates occurred in 1: 3 and 1: 1 (WE: pine bark) mixes. At concentrations over 50%, increases in bulk density and reductions in volume and percent air space in WE substrates were severe enough to negatively impact root growth and plant quality.

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Wet Earth (WE) is a recycled paper product being tested as a potential plant growth substrate. It is composed of 80% recycled paper, 18% diatomaceous earth, 1% CaO, and 1% humic acid by volume. Use of WE by commercial growers would reduce demand for both landfill space and for slowly renewable resources such as peat and pine bark. Evidence also suggests that WE reduces nitrate runoff. Objectives included: determining effects of WE on plant growth, examining effects of WE on NO3 and NH4 runoff from container plant production, and determining the chemical and physical properties that characterize WE as a growth substrate. Ratios of pine bark to WE tested were 100% pine bark, 1:3, 1:1, 3:1, and 100% WE by volume. Fertilizer treatments included: 100% of the recommended rate of controlled release fertilizer (CRF), 50% CRF plus 50% liquid fertilizer (LF) and 100% LF. Plant heights, widths, and visual quality ratings were obtained monthly throughout the 16-week experiment. Leaf, shoot and root dry weights were determined at harvest. Nitrogen content of roots, shoots, and substrates were determined at planting and harvest, while NO3 and NH4 content of leachate was determined at each irrigation. All substrates were analyzed at planting and harvest for pH, soluble salts, exchangeable cations, and CEC. Changes in volume, bulk density, porosity, and air space were also measured. Plant size and quality varied significantly between substrate mixes. Mortality was significantly higher in mixes containing 75% and 100% WE. Changes in volume, bulk density, and percent air space were also significant and inversely related to WE concentration.

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Uniform rooted cuttings of pyracantha (Pyracantha coccinea M.J. Roem. 'Lalandei') were potted into 3.8 liter containers in a pine bark:sand medium. Plants were treated with a medium drench at 0.5 mg ai per container, or a foliar spray at 150 mg ai per liter, or no uniconazole. Plants also were exposed to one of three irrigation regimes: nonstressed, stressed or acclimated. Uniconazole had little effect on leaf water potential, osmotic potential, transpiration or leaf conductance. The uniconazole drench treatments reduced plant growth and increased N, Ca, and Mn concentrations in the leaves. Foliar applications had less effect on plant growth and elemental content Acclimated and stressed plants had lower water and osmotic potentials, transpiration rates and leaf conductance than nonstressed plants on the final day of the stress cycle. Acclimated plants had higher levels of N and Mn with lower levels of Zn in the leaves than either stressed of nonstressed plants.

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Commercially propagated `Halward's Silver' spirea (Spiraea nipponica Maxim.) bareroot cuttings and cuttings with substrate around the roots (plugs) were transplanted into 3.8-L containers and fertilized with various P fertilizers to determine the effect of fertilizer source on P leaching and plant growth. The following fertilizer treatments were applied: 1) 100% of the recommended rate of P from controlled-release fertilizer (CRF), consisting of 22N-2.6P-10K; 2) 100% of P from triple superphosphate (TSP, 0N-20P-0K) with N and K provided by 22N-0P-10K CRF; and 3) 50% of P from CRF, consisting of 22N-1.3P-10K, plus 50% of P from TSP (CRF/TSP). The most P leached from cuttings transplanted as plugs or bareroot and fertilized with TSP, while the least P leached from cuttings transplanted as plugs and fertilized with CRF or CRF/TSP. Plants fertilized with CRF/TSP generally had larger root dry weights than did plants fertilized with CRF or TSP. Plants fertilized with CRF had the smallest stem dry weights. Shoot-to-root (S/R) ratio was largest in plants transplanted as plugs in substrate amended with TSP, but cuttings transplanted bareroot into CRF-amended substrate had the highest S/R ratio and the lowest stem P concentration. Incorporation of CRF/TSP into the container substrate can reduce P leaching compared with incorporation of TSP, and can increase root and stem dry weights of plants transplanted as plugs compared with incorporation of CRF.

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