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A study was conducted with Prunus × incamp `Okame' to evaluate the effects of a pot-in-pot production system compared to a conventional above-ground system and cyclic irrigation on plant growth and water loss. Plants were grown in #7 (26-L) containers with a 8:1 pinebark:sand (v/v) substrate. Cyclic irrigation provided the same total volume of water, but was applied one, three, or four times per day. Final plant height and stem diameter, shoot and root dry weight, total biomass, and root:shoot ratio were all increased for plants grown pot-in-pot compared to above-ground. Multiple irrigation cycles increased stem diameter, shoot dry weight, and total biomass, compared to a single irrigation application. Multiple irrigation cycles decreased the root:shoot ratio. Evapotranspiration was influenced by production system, irrigation, and date. Amount of water lost as leachate was influenced by irrigation and date. Cyclic irrigation resulted in a two-fold decrease in leachate volume. Soluble salts and nitrate-nitrogen in the leachate were influenced by an interaction between production system, irrigation, and date.
A study was conducted with Magnolia grandiflora `St. Mary' to evaluate the effects of a pot-in-pot production system compared to a conventional aboveground production system and containers treated with or without copper hydroxide (Spin Out™). At 4 and 12 months after beginning the study, plants grown pot-in-pot were taller than plants in the conventional system. Stem diameters of plants grown pot-in-pot were also larger at 12 months. Production system influenced root dry weight in the outer 50% of the container, total root dry weight, percent root dry weight in the inner 50% of the container, percent root dry weight in the outer 50% of the container, and total biomass. Production system had no effect on shoot dry weight. Treatment with copper hydroxide had no effect on root or shoot growth. Production system and copper treatment influenced degree of root coverage. Plants grown pot-in-pot had higher rates of Ps and gs with increased Ci levels compared to plants above-ground. Production system had no effect on calculated transpiration rates.
Decline of certain container-grown ornamental species during the hottest months of summer is a common problem for nurserymen in the southeastern United States. When roots are killed due to high root-zone temperatures and growth ceases, production of plant hormones also decreases. A study was conducted with Early Harvest PGR (Griffin LLC, Valdosta, Ga.), which contains cytokinins, gibberellic acid, and indole butyric acid, to determine if this product would improve the growth of five ornamental species that typically decline during the summer in south Georgia nurseries. The species used were Cotoneaster dammeri Schneid. `Coral Beauty', Cotoneaster salicifolius Franch. `Green Carpet', Spiraea japonica L. `Shirobana', Thuja occidentalis L. `Little Giant', and Weigela florida (Bunge) A. DC. `Minuet'. The treatments (control, 1.5 and 3.0 mL Early Harvest PGR/1125 mL water) were applied every 2 weeks from mid-June until mid-Sept. 1999 as a foliar drench. Treatment of both Cotoneaster species and the Thuja with Early Harvest PGR resulted in little influence on plant growth. While growth indices did not increase, shoot dry mass of Spiraea and Weigela increased 17% and 26%, respectively, when treated with Early Harvest PGR at the medium rate. Plant quality ratings for Spiraea increased when the 1.5-mL rate of Early Harvest PGR was applied. A rate of 3.0 mL of Early Harvest PGR on Spiraea decreased shoot and root dry mass, total biomass, root ratings, and final plant quality. Root ratings and plant quality were highest for Weigela grown with the 1.5-mL Early Harvest PGR treatment. These results indicate that treatment of woody ornamentals with Early Harvest PGR for positive results is both species- and rate-dependent.
A study was conducted to compare four different controlled-release fertilizers when used in conjunction with Tex-R Geodiscs on the growth of Ilex crenata Thunb. ex J.A. Murray `Compacta' in 3.8 L (#1) containers. The fertilizers used were Osmocote Plus Southern Formula (18N-3.9P-10K), Osmocote Plus Northern Formula (18N-3.9P-10K), Wilbro (15N-1.7P-7.5K), and Nutricote T-360 (17N-2.6P-6.6K) all applied at the rate of 1.8 kg N/m3. Geodisc treatments were: 1) no disc, 2) fertilizer placed on top of the disc, and 3) fertilizer placed beneath the disc. At 2 and 4 months after the initiation of the study, the growth indices for plants grown with both Osmocote Plus fertilizers were larger than for either of the other two fertilizers. After 7 months, final growth indices were greater for the Osmocote Plus and Wilbro treatments compared to Nutricote. Final leaf, stem, and root dry masses were all greater for the Osmocote Plus fertilizers compared to the other two, as was final plant quality. Plants with fertilizer placed on top of the disc were smaller compared to the no disc or beneath the disc treatments. Geodisc treatment had no influence on shoot dry mass or final plant quality. Data for leachate nutrient analysis and evapotranspiration will also be presented.
Membrane thermostability of Heritage river birch (Betula nigra L. Heritage) was measured by electrolyte leakage from excised roots of plants grown in pot-in-pot (PIP) and conventional aboveground production systems (CPS). The predicted critical midpoint temperature (Tm) for a 30-min exposure was 54.6 ± 0.2 °C for PIP and 56.2 ± 0.6 °C for CPS plants. Plants grown PIP had a steeper slope through the predicted Tm, suggesting a decreased tolerance to high root-zone temperatures in relation to plants grown aboveground. Since the root systems of Heritage river birch grown PIP are damaged at lower temperatures than plants grown aboveground, growers should prevent exposure of root systems to high temperatures during postproduction handling of plants grown PIP.
Mouse ear (leaf curl, little leaf, squirrel ear) has been a problem for growers of container-grown river birch (Betula nigra L.) since the early 1990's. Mouse ear has been noticed in several southeastern States as well as Minnesota, Ohio, Oregon, and Wisconsin, making it a national problem. The disorder is easy to detect in nurseries as the plants appear stunted. The leaves are small, wrinkled, often darker green in color, commonly cupped, and have necrotic margins. New growth has shortened internodes which gives plants a witches-broom appearance. Plants growing in native soil rarely express the disorder. Several common micronutrients have been evaluated with no results. A trial was initiated in June, 2003 to determine if nickel deficiency was the cause of mouse-ear. Symptomatic river birch trees growing in a pine bark substrate in containers were treated with foliar applications of nickel sulfate and a substrate drench. Topdress applications of superphosphate (0-46-0) and Miloroganite, products known to contain nickel, were also applied. At 16 days after treatment (DAT), up to 5 cm of new growth occurred on plants sprayed with nickel sulfate and foliar concentrations of nickel in the new growth increased five fold compared to control plants. At 30 DAT, shoot length increased 60%, leaf area increased 83%, and leaf dry mass increased 81% for trees receiving a foliar application compared to non-treated control plants. Treating trees with a substrate drench alleviated symptoms, whereas treatment with superphosphate and Milorganite did not. Trees receiving a foliar or drench application had normal growth for the remainder of the growing season. Additional studies are underway to refine methods of application, rates, and sources of nickel suitable for use.
A study was conducted with Dendranthemum ×grandiflorum (Ramat.) Kitamura garden chrysanthemum (`Grenadine', `Nicole', and `Tolima') to evaluate the growth and flowering of these plants grown in 2.6-L (no. 1) black plastic containers compared to plants grown in fiber containers with Cu(OH)2 impregnated into the container walls. For all three cultivars, growth indices, shoot and root dry weights, and total biomass increased for plants grown in fiber containers. Total number of flower buds per plant increased 30% to 32% for `Grenadine' and `Nicole' and 53% for `Tolima' grown in fiber containers. Plants grown in Cu(OH)2-impregnated fiber containers had less root coverage at the container:growing medium interface and no observable root circling in contrast to visible root circling on plants grown in black plastic containers. Foliar nutrient analysis on `Grenadine' showed that K decreased and Fe and Cu increased when grown in Cu(OH)2-impregnated fiber containers. No visible nutrient abnormalities were seen in this study.
A study was conducted with Lagerstroemia indica x fauriei `Acom a' to evaluate methods for reducing rooting-out problems in a PIP production system. The products tested were Biobarrier™, a geotextile fabric impregnated with trifluralin; Root Control'” fabric bag material; and Spin Out™, a commercial formulation of copper hydroxide (7.1%) in latex paint. Biobarrier™ reduced plant height, shoot dry weight, percent root dry weight outside of the planted container and total biomass compared to the non-treated control. For the control, 7.1% of the total root dry weight was found between the holder pot and planted container compared to 0.2% for the Biobarrier™ treatment. When the holder pot and planted container or the planted container and Root Control™ fabric were both treated with Spin Out™, plant height and shoot dry weight were reduced. Spin Out™ reduced root circling on the sidewalls of the planted containers but not on the bottom of the containers. All treatments except the control reduced rooting-out to a degree that allowed for the manual harvesting of the planted container from the holder pot after seven months in the field.
Granular and liquid formulations of paclobutrazol were tested to evaluate the growth and flowering response of butterfly bush (Buddleia davidii Franch. 'Dubonnet'). At the rates tested (5, 10, 20, and 40 mg ai·pot–1), the granular formulation reduced the growth index, plant height, shoot dry weight, total plant biomass, number of panicles and panicle length to a greater degree than the liquid formulation applied as a drench. Both formulations reduced total plant biomass and increased the root:shoot ratio compared to the control. All rates of the granular formulation above 5 mg ai · pot–1 produced non-marketable plants. Since no phytotoxicity was observed with any treatment, the application of paclobutrazol to control the growth of butterfly-bush may be useful if the correct formulation and rate of application are chosen.
Membrane thermostability of `Needlepoint' Chinese holly (Ilex cornuta Lindl. & Paxt.), `Albo-marginata' English holly (Ilex aquifolium L.), and `Nellie R. Stevens', an Ilex aquifolium × Ilex cornuta hybrid, was determined by measuring electrolyte leakage in excised leaves and roots. The critical midpoint heat-killing temperature (T,) after a 30-min exposure was 54.4 ± 0.4C for `Nellie R. Stevens' leaves and was ≈ lC higher than that for Chinese (52.9 ± 0.3C) or English holly (52.9 ± 0.4C). The Tm for English holly roots (53.9 ±_ 1.5C) was higher than that for either `Nellie R. Stevens' (51.7 ± 0.3C) or Chinese holly (50.1 ± 0.3C). The results of this study suggest that English holly and `Nellie R. Stevens' leaves and roots can withstand direct heat injury equal to or greater than that of Chinese holly.