Effects of Pinching, Number of Cuttings per Pot, and Plant Growth Regulators on Height Control of Purple Firespike

Abstract

<jats:p>Purple firespike (<jats:italic>Odontonema callistachyum</jats:italic>), native to Central America, has potential for use as a new flowering potted plant. The effects of number of pinches (zero, one, or two) and number of cuttings (one, two, or three) per 6-inch pot were evaluated on the control of plant height. Plant height was suppressed as the pinch number increased. The greatest reduction was recorded with one cutting per pot and two pinches. The maximum number of branches per pot was recorded with two pinches and three cuttings per pot. In a second experiment, plant growth regulators (PGR) were also tested for efficacy of height control; 2 weeks after pinching, foliar sprays of paclobutrazol, flurprimidol, daminozide, chlormequat, and a tank-mix of daminozide + chlormequat or media drenches of paclobutrazol, uniconazole, or flurprimidol were applied. Plant height, leaf area, and leaf dry weight were recorded at 3, 6, and 9 weeks after PGR application. Maximum height control was obtained with uniconazole drench at 8 ppm, resulting in plants 22 cm tall, 61% shorter than the untreated control (56 cm); however, it resulted in severe leaf distortion. Plant height was 56% and 46% shorter than the control using drenches of paclobutrazol at 30 ppm and flurprimidol at 15 ppm, respectively. Daminozide spray at 2000 ppm and tank-mix of daminozide + chlormequat at 4500/1500 ppm suppressed stem elongation by 20.3% and 19%, respectively. Plants treated with paclobutrazol drench at 30 ppm reduced leaf area and leaf dry weight compared with other PGRs. Chlormequat spray at tested concentrations was ineffective for controlling firespike plant growth. The most attractive potted plants were produced using a drench application of paclobutrazol at 10 or 15 ppm.</jats:p>

Average Daily Temperature Effects on Paclobutrazol Efficacy of Four Floriculture Crops

“…These results were consistent with other research that demonstrated PGRs to be species-or even varietydependent (Barrett, 2001;Currey and Erwin, 2012;Hammond et al, 2007;Sprzaczka and Laskowska, 2013). In almost all cases, DW decreased as PBZ increased within an ADT, which is consistent with other recent research as well (Rezazadeh and Harkess, 2015). Table 3.…”

Effect of Plant Growth Regulators on Growth and Flowering of Potted Red Firespike

“…Paclobutrazol drenches ‡1.2 mg/pot and all rates of flurprimidol drenches were more effective in reducing plant dry weight than spray applications of all tested PGRs and the control (Table 1). Decreases in leaf area and dry weight after PGR applications have also been reported in cucumber [Cucumis sativus (Cho et al, 2002)] and purple firespike (Rezazadeh and Harkess, 2015).…”

“…Sanderson et al (1988) compared five application methods of paclobutrazol and reported a substrate drench was the most effective method for controlling plant height. In a study on purple firespike (Odontonema callistachyum), plant height was 56% and 46% shorter than the control using drenches of paclobutrazol and flurprimidol at 3.35 and 1.77 mg/pot, respectively (Rezazadeh and Harkess, 2015). Flurprimidol is effective as a foliar spray or substrate drench for height control (Currey and Lopez, 2011;Krug et al, 2005).…”

Substrate Drench Applications of Flurprimidol and Paclobutrazol Influence Growth of Swamp Sunflower

“…Another comparison by Vernieri et al (2003) found flurprimidol at 60 mgÁL -1 applied as a foliar spray on sunflower was less effective on height reduction than a low dose of paclobutrazol (2 mg/ pot) applied as a substrate drench. Application of flurprimidol in other species as a drench rather than spray has been shown to produce more ideal plant effects, including reduction in plant size, while not affecting flowering time or flower size (Krug et al, 2005a(Krug et al, , 2005bRezazadeh and Harkess, 2015;Whipker et al, 2006).…”