No abstract

Cutless (flurprimidol) effectively reduced shoot elongation of container-grown woody ornamentals, including abelia, cotoneaster, crape myrtle, Foster holly, Mystery gardenia, Manhattan euonymus, photinia and rhododendron. Optimum Cutless 50W (flurprimidol) spray rates were 500–600 ppm for most species except for Manhattan euonymus (1250 ppm), Mystery gardenia and Natchez crape myrtle (750 ppm). Optimum Cutless 0.33G (flurprimidol) granular rates were 0.6 kg/ha (0.5 lb/A) for Coral Beauty cotoneaster and Foster holly, and 1.7 kg/ha (1.5 lb/A) for Fraser photinia. Atrimmec (dikegulac) was effective in controlling growth of abelia at spray rates of 1480 ppm, Coral Beauty cotoneaster, and Manhattan euonymus at 1600 ppm, Foster holly, and Fraser photinia at 4440 ppm. Neither Off-Shoot-O nor Trim-Cut (mefluidide) had a significant effect on any of the species studied. None of the growth regulators had a significant effect on nandina.

Several species of large, established landscape shrubs were treated with different concentrations of Cutless (flurprimidol) or label concentrations of Atrimmec (dikegulac) or Trim-cut (mefluidide). Length of new shoots decreased with increasing rates of Cutless for ‘Convexa’ holly, ‘Hetzi’ juniper, Japanese cleyera, ‘Manhattan’ euonymus, thorny elaeagnus, and yaupon holly, but for most species the Cutless treatments were not as effective as Atrimmec. The 5000 ppm Cutless foliar spray was the most effective treatment for Manhattan euonymus but Atrimmec was more effective on thorny elaeagnus, ‘Convexa’ holly, yaupon holly, and Japanese cleyera. Trim-cut (1600 ppm) reduced growth of thorny elaeagnus and ‘Convexa’ holly, but not as much as Atrimmec (5000 ppm).

Wounding, indole butyric acid (IBA) and trimming of cuttings to a basal node were evaluated for their effects on rooting of Buxus sempervirens L. (American boxwood), B. sempervirens L. ‘Suffruticosa’ (English boxwood), B. microphylla var. koreana Nakai. (Korean boxwood), and B. microphylla var. japonica (Müll. Agr.) Rehd. and Wils. (Japanese boxwood) cuttings. Rooting of all cultivars was improved by a 5 second dip in a 0.4% aqueous solution of the potassium salt of IBA. Wounding the basal end of the cuttings only improved rooting for Korean and Japanese boxwoods. However, the combination of wounding and IBA dip gave the best results for all cultivars. Trimming the cuttings to a basal node was beneficial only to Korean boxwoods.

A study was conducted to compare the growth-retarding effects of paclobutrazol (Bonzi), uniconizole (XE-1019, Sumagic), and daminozide (B-Nine) on container-grown bedding plants. Seedlings of Begonia semperflorens ‘Olympia’, ‘Scarletta’, and ‘Vodka’, Catharanthus roseus ‘Little Bright Eye’, Impatiens sultani ‘Blitz Orange’, and Zinnia elegans ‘Yellow Marvel’ were treated with a paclobutrazol spray at 0.15, 0.3 or 0.45 mg ai/plant, or a drench of 0.15 mg ai/pot. Uniconizole was applied as a spray at 0.025, 0.05, or 0.075 mg ai/plant, or a drench of 0.025 mg ai/pot. The daminozide was applied only as a 5000 ppm spray. Paclobutrazol and uniconizole were very effective in controlling the height of begonia, catharanthus (vinca), and impatiens at relatively low rates compared to daminozide. The height of zinnia was controlled by daminozide, but not by the other compounds at the rates tested.