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Jeffrey G. Norcini and James H. Aldrich

The response of `Barbara Karst' bougainvillea to the chemical pinching agent Off-Shoot-O® (OSO; methyl esters of fatty acids), was evaluated. Liners were transplanted 4 Apr. 1994 into 3.8-liter containers of soilless medium. OSO at 0 (+pruning), 7.8, 15.6, 31.2, 62.5, 125, and 250 ml·liter–1 was applied over the top on 24 May to 20 replications per OSO concentration and 10 replications per control. On 25 May, OSO was reapplied to 10 replications per OSO concentration. Treatments were applied using a compressed-air backpack sprayer that delivered 82 + 3 and 93 ± 2 liter·ha–1 at 2.8 kg·cm–2 on 24 and 25 May, respectively. Crown phytotoxicity was recorded 1, 2, 7, and 13 days after the initial application on a scale of 0 = no injury to 10 = plant death. A growth index and number of stems <5, 5 to <10, 10 to <15, and >15 cm long were recorded 23 May and 7 July. The best overall response was to the 15.6 + 15.6 ml·liter–1 application, despite the slight but commercially acceptable foliar injury (mean rating = 2.3+0.2). This treatment was similar to the pruned control in growth and number of stems.

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Terri Woods Starman

Manually and chemically pinched plants of 18 cultivars of Impatiens hybrids (Kientzler New Guinea impatiens) were compared to control plants to determine the effect of shoot apex removal on flowering, plant size, and branching characteristics. Either pinching treatment delayed flowering by ≈3 days compared with nonpinched controls. Pinching had no effect on plant height or fresh or dry weight. Plant diameter and form changes due to pinching depended on cultivar. Total branch count was increased by chemical but not manual pinching although both pinching methods affected mode of branching. The 18 cultivars of Kientzler New Guinea impatiens were best grown as 0.4-liter potted plants without the aid of pinching.

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Amir Rezazadeh, Richard L. Harkess, and Guihong Bi

et al., 2013 ), thereby chemical pinching has been used to enhance lateral branching. Application of PGRs is generally less labor intensive than hand pinching; however, PGRs may cause phytotoxicity ( Meijón et al., 2009 ). Plant growth regulators with

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Bruce L. Dunn, Stephen Stanphill, and Carla Goad

This study aimed to identify the best method to improve poor branching of poinsettia ‘Orange Spice’. Treatments included pinched and unpinched alone and in combination with four different rates (3.9, 7.8, 11.7, and 23.4 mL⋅L−1) of Atrimmec. Pinching reduced plant height, as did unpinched + 11.7 mL⋅L−1 and unpinched + 11.7 mL⋅L−1 Atrimmec. Neither pinching nor Atrimmec had any effect on plant width, stem caliper, or shoot dry weight. Atrimmec did not increase the number of laterals in combination for pinched or unpinched treatments, but unpinched plants generally produced more laterals. Unpinched with any rate of Atrimmec resulted in tertiary shoots, which improved the visual appearance and quality.

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J.G. Norcini, J.M. McDowell, and J.H. Aldrich

The use of dikegulac foliar sprays in production of 4.5-liter hanging baskets (25.4-cm in diameter) of `Barbara Karst' bougainvillea [Bougainvillea ×buttiana (Bougainvillea glabra Choicy X Bougainvillea peruviana Humb. & Bonpl.) `Barbara Karst'] and `Rainbow Gold' bougainvillea (Bougainvillea `Rainbow Gold') was investigated under high temperatures (27.5-32C) and two production seasons (late spring to early summer and midsummer to early fall). During the late production season, liners pruned at transplanting (0 weeks) and treated with 1600 mg dikegulac/liter at 0 and 4 weeks resulted in plants with more flowers than that of controls (pruned only at 0 and 4 weeks), with `Barbara Karst' having a slightly compact, pendulous growth habit similar to that of controls. Dikegulac enhanced flowering compared with controls during midspring to early summer, but it did not result in plants with a slightly compact pendulous growth habit. These results suggest that a foliar spray of 1600 mg dikegulac/liter could substitute for the second pruning during hanging basket production of `Barbara Karst'. Chemical name used: sodium salt of 2,3:4,6-bis-O-(1-methylethylidene)-α-xylo-2-hexulofuranosonic acid (dikegulac-sodium).

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J.G. Norcini, J.H. Aldrich, and J.M. McDowell

Foliar spray application of dikegulac at 1600 mg·liter-1 during production of Bougainvillea glabra Choicy `Mauna Kea White', and Bougainvillea `Raspberry Ice', `Royal Purple', `Summer Snow', and `Temple Fire' in 4.5-liter hanging baskets (25.4 cm in diameter) was investigated in relation to flowering. The effect of foliar-applied dikegulac at 0, 400, 800, 1200, and 1600 mg·liter-1 on bracteole size of `Mauna Kea White' was also determined. Liners of `Temple Fire' pruned at transplanting (0 weeks) and sprayed with dikegulac at, 0 and 4 weeks had increased flowering and a slightly more compact, pendulous growth habit than plants that had only been pruned at 0 and 4 weeks. Dikegulac had little to no effect on flowering of the other cultivars. Under late-spring to early summer conditions (generally increasing temperatures), bracteole size of `Mauna Kea White' was reduced ≈25 % by 400 mg dikegulac/liter compared to nontreated plants; 800 to 1600 mg dikegulac/liter reduced bracteole size ≈37%. Under late-summer to mid-fall conditions when the weather was cooler and wetter, dikegulac had little to no effect on bracteole size; however, bracteoles of nontreated plants were ≈25% smaller than those of plants grown under the warmer and drier conditions of late spring to early summer. Chemical name used: sodium salt of 2,3:4,6-bis -O- (1-methylethylidene) -α-l-xylo- 2-hexulofuranosonic acid (dikegulac).

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Terri Woods Starman

Manually pinched plants of 18 cultivars of Impatiens hybrids (Keintzler New Guinea impatiens) were compared to control plants to determine the effect of apical meristem removal on flowering, growth and branching. Pinching delayed days to anthesis (first flower) of all cultivars, however, further delay in days to marketability (5 flowers open) was dependent upon cultivar. Plant area and fresh and dry weight were not affected by pinching plants of any cultivar. Cultivar influenced response to pinching treatments for plant height and plant width. Secondary branch number was increased by approximately 3 branches for all cultivars when plants were pinched. There were interactions between cultivar and treatment for primary, tertiary, and total branch number. Measured improvements in plant form determined two cultivars, Sylvine and Thecla, should be pinched. Chemically pinching these two cultivars with dikegulac at 780 mg·liter-1 was comparable to manually pinching plants.

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Fabienne Gauthier, Blanche Dansereau, and Marie-Josee Lambert

During Fall 1995–Winter 1996, rooted cuttings of eight Rhododendron Simsii cultivars—Dorothy Gish, Jacinth, Paloma, White Gish, Friedhelm Scherrer, Gloria, Helmut Vogel, and Inga were transplanted July 1995 into 10.5-cm pots. A treatment consisted of one, two or three cuttings per pot. Cuttings were pinched either mechanically using a hedge clipper (control) or chemically with Off-Shoot-O at rates of 63.5 or 111.1 mL·L–1 of water or with Atrimmec at 20 mL·L–1 of water. Pinching treatments were repeated three times during the experimental period. New secondary shoots developed more rapidly after a mechanical pinch than after a chemical pinch. Moreover, greater foliage damage was observed on plants pinched with Off-Shoot-O. Growth measurements (height and diameter of plants, top dry mass, number of days to reach anthesis and visual quality) will be presented.

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Diana R. Cochran and Amy Fulcher

phytotoxicity ( Meijón et al., 2009 ) and be perceived as digressing from sustainable production ( Lütken et al., 2012 ). Plant growth regulators have several modes of action, including branch inducing, chemical pinching (chemicals that suppress apical dominance

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Diana R. Cochran, Amy Fulcher, and Guihong Bi

( Hammond et al., 2007 ), increasing branch number ( Holland et al., 2007 ), and increasing flower number ( Abdelgadir et al., 2010 ). However, since the introduction of chemical pinching agents in the 1960s ( Cathey et al., 1966 ), there has been an ongoing