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Chris A. Martin, Dewayne L Ingram, and Terril A. Nell

Trees were grown for 2 years as a function of three container volumes (10, 27, and 57 liter) the first year and six shifting treatments (10 liter both years, 10 to 27 liter, 10 to 57 liter, 27 liter both years, 27 to 57 liter, or 57 liter both years) the second year when containers were spaced 120 cm on center, Height and caliper were greatest for magnolias grown in 27- or 57-liter containers both years. Caliper was greater for trees shifted from 10-liter containers to the larger container volumes compared to trees grown in 10-liter containers both years, Trees grown in 10-liter containers both years tended to have few roots growing in the outer 4 cm at the eastern, southern, and western exposures in the grow medium, During the second year, high air and growth medium temperatures may have been primary limiting factors to carbon assimilation during June and August. Using large container volumes to increase carbon assimilation and tree growth may be even more important when daily maximum air temperatures are lower during late spring or early fall compared to midsummer.

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Chris A. Martin, Dewayne L Ingram, and Terril A. Nell

Trees were grown for 2 years as a function of three container volumes (10, 27, and 57 liter) the first year and six shifting treatments (10 liter both years, 10 to 27 liter, 10 to 57 liter, 27 liter both years, 27 to 57 liter, or 57 liter both years) the second year when containers were spaced 120 cm on center, Height and caliper were greatest for magnolias grown in 27- or 57-liter containers both years. Caliper was greater for trees shifted from 10-liter containers to the larger container volumes compared to trees grown in 10-liter containers both years, Trees grown in 10-liter containers both years tended to have few roots growing in the outer 4 cm at the eastern, southern, and western exposures in the grow medium, During the second year, high air and growth medium temperatures may have been primary limiting factors to carbon assimilation during June and August. Using large container volumes to increase carbon assimilation and tree growth may be even more important when daily maximum air temperatures are lower during late spring or early fall compared to midsummer.

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Lori A. Black, Terril A. Nell, and James E. Barrett

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James E. Barrett, Carolyn A. Bartuska, and Terril A. Nell

Paclobutrazol drench treatments were evaluated for efficacy on Caladium ×hortulanum (Birdsey) cultivars Aaron, White Christmas, and Carolyn Wharton. Drenches at 2.0 mg/pot did not reduce height of `Aaron' and `White Christmas' plants when applied 1 week after planting, but 2.0 mg applied at 3 weeks after planting did result in shorter plants. The difference for time of application may be due to the amount of roots present to take up paclobutrazol when applied. In two factorial experiments, there were no interactions between cultivar and time of application or amount of chemical. Paclobutrazol at 0.5 mg/pot resulted in plants that were shorter than the controls. Higher amounts of paclobutrazol provided additional reductions in height, but there was variation between the experiments for degree of effect with amounts >1 mg. Generally, commercially acceptable height control was provided by paclobutrazol drench treatments at 0.5 and 1.0 mg/pot applied 3 weeks after planting. Chemical names used: (2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-1,2,4-triazol-1-yl-pentan-3-ol (paclobutrazol).

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James E. Barrett, Carolyn A. Bartuska, and Terril A. Nell

Four experiments using container-grown Dendranthema ×grandiflorum (Ramat.) Kitamura `Nob Hill' or `Tara' were conducted to determine effects of application site and spray volume on uniconazole efficacy. Uniconazole applied only to mature leaves was less effective in controlling stem elongation than were stem applications, whole-plant sprays, or medium drenches. Spray volume altered efficacy more for uniconazole than for daminozide. Also, the effect of uniconazole spray volume was greater when the medium was not covered than when covered to prevent spray solution entering medium. Results from these studies showed the efficacy of uniconazole increased with increased stem coverage and with amount of chemical reaching the medium, which was achieved with high spray volumes. Chemical names used: (E)-1-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl-1-penten-3-ol) (uniconazole); butanedioic acid mono (2,2-dimethylhydrazide) (daminozide).

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Ahmed A. Al-Badawy, James E. Barrett, and Terril A. Nell

Paclobutrazol was applied as soil drench to potted petunia, and the treated plants were shorter than untreated ones. Three types of compost were then made from the treated and untreated plants: the shoots, the medium (including roots), and both shoots and medium. They were mixed with Vergro Klay Mix at the ratios of 0%, 5%, 10%, 20%, and 40% (v/v). In a factorial experiment, plugs of Begonia semperflorens cv. Gin were planted in the media with compost. Plants grown in media containing paclobutrazol residue were shorter and had less dry weight compared to those grown in media containing no paclobutrazol residue. Compost ratios at 5% and 40% reduced plant height to 65% and 42% and shoot dry weight to 55% and 20% of the control plants, respectively. These results indicate that residues from plants treated with paclobutrazol may carry over in soil of landscape beds and affect the growth of subsequent crops grown in that soil.

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James E. Barrett, Carolyn A. Bartuska, and Terril A. Nell

Experiments with' White Christmas' and `Carolyn Wharton' caladiums (Caladium × hortulanum Birdsey), croton (Codiaeum variegatum), brassaia (Brassaia actinophylla Endl.), `Annette Hegg Dark Red' poinsettia (Euphorbia pulcherrima Wind.), and `Super Elfin Red' and `Show Stopper' impatiens [Impatiens wallerana (L.) Hook.f.] determined effectiveness of paclobutrazol in solid spike form as compared to media drench applications for height control. Paclobutrazol drenches and spikes were effective for all crops tested, with a similar concentration response for all, except that drenches had greater efficacy than spikes on caladium. A reduced effect was observed when spikes were placed on the medium surface of `Super Elfin Red' impatiens, while placement in the middle of the pot or around the side was equally effective. These results indicate that the spike formulation of paclobutrazol has potential to provide adequate size control for floriculture crops with the possible exception of rapidly developing crops, such as caladiums. Chemical name used: (2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-1,2,4-triazol-1-yl-) penten-3-ol (paclobutrazol).

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Ahmed A. Al-Badawy, James E. Barrett, and Terril A. Nell

To evaluate importance of paclobutrazol residues on surfaces, begonia (Begonia semperflorens) cv. Whisky and chrysanthemum (Dendranthema grandiflora) cv. Coral Davis plants were grown in flats sprayed with paclobutrazol at 0, 50, 100, 200 and 400 ppm.

For begonia, the plant heights at 2 and 4 weeks after treatments were decreased by 39 to 49% and by 55-69%, respectively. The overall change in height ranged from 2.1 to 4.9 cm compared to 15.3 cm for the control plants.

For chrysanthemum, a reduction in plant height was observed and the overall change in height ranged from 2.9 to 5.6 cm compared to 28.8 cm for the control plants.

Based on these results, there is a potential for paclobutrazol to affect non-target plants when subirrigation is used.

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José A. Monteiro, Terril A. Nell, and James E. Barrett

The effect of two temperature regimes (29 °C day/24 °C night and 24 °C day/18 °C night) and of a 4-hour night interruption, during production, was studied on postproduction flower longevity and bud drop of 'Meirutral' and 'Meidanclar' potted, miniature roses (Rosa L. sp.). High production temperatures increased postproduction flower longevity and decreased postproduction bud drop. In 'Meidanclar', the high production temperature increased incidence of malformed flowers. No effects of night interruption could be shown on either postproduction flower longevity or bud drop.

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José A. Monteiro, Terril A. Nell, and James E. Barrett

Five cultivars of potted miniature roses (`Candy Sunblaze', `Lady Sunblaze', `Orange Sunblaze', `Red Sunblaze' and `Royal Sunblaze') were grown until stage 1 (bud showing color with sepals starting to unfold). At this stage one half of the plants were moved to interior conditions (12 μmol s-1 m-2 from cool white fluorescent lights for 12 hr daily and 21 ± 1C) and the other half were maintained in the greenhouse at recommended production conditions. Stage 1 bud respiration, flower respiration at flowering and at 2, 4, 6 and 8 days after flowering were assessed for plants in the greenhouse and under interior conditions. Also, flower interior longevity was assessed for all the cultivars and the correlations between flower longevity and flower respiration at the different stages were analyzed. At flowering and under interior conditions `Red Sunblaze' lasted the longest (23 days) followed by `Orange Sunblaze' (18 days), `Lady Sunblaze' and `Candy Sunblaze' (16 days), and `Royal Sunblaze' (13 days) and flower respiration was 2.08, 2.74, 3.91, 3.59 and 3.94 mg CO2 g-1 hr-1, respectively. In miniature rose, flower longevity was negatively correlated with flower respiration rate (P = 0.01).