Lantana is popular for its growth and flowering throughout the heat of summer and, while it is a tender woody perennial, is most commonly used as an herbaceous annual (Armitage, 2001; Dole and Wilkins, 2005; Nau, 2011). Flower colors vary, ranging from yellow to deep red and purple, and foliage with green or variegated leaf margins. In addition, growth habits for different lantana cultivars vary from dwarf, highly compact cultivars for containers to large cultivars for use in landscapes. Container-produced lantana may require PGR applications to produce proportionately sized plants.
PGRs are useful in controlling growth of containerized ornamental crops produced in greenhouses (Dole and Wilkins, 2005; Gaston et al., 2001; Whipker et al., 2011). Commercial recommendations for controlling lantana are to apply foliar sprays containing chlormequat chloride every 2 weeks starting ≈1 week after pinching (Nau, 2011). Numerous studies report the effect of foliar sprays containing chlormequat chloride, chlormequat chloride and daminozide, ethephon, paclobutrazol, and uniconazole (Barrett and Schoellhorn, 2001; Kamoutsis and Matsoukis, 2003; Matsoukis et al., 2004; Matsoukis and Chronopoulou-Sereli, 2005; Ruter, 1996).
Applying PGRs with substrate drenches can provide longer growth control when compared with foliar sprays (Gent and McAvoy, 2000; Whipker et al., 2011). We have found few reports of using substrate drenches for controlling excessive growth of lantana in containers (Barrett and Schoellhorn, 2001; Ruter, 1996). Barrett and Schoellhorn (2001) reported that paclobutrazol and uniconazole effectively suppressed ‘Trailing Lavender’ lantana width. Similarly, Ruter (1996) reported that paclobutrazol drenches inhibited growth of ‘New Gold’ lantana. Although informative, these studies on two cultivars and a narrow range of concentrations of two active ingredients are the only reports on using PGR drenches for controlling lantana growth.
The limited information on using PGR drenches to control growth of lantana is promising. Therefore, a broader understanding of the interaction between cultivar, active ingredient, and concentration would improve the use of substrate drenches for growth control. Our objective was to quantify the efficacy of different PGR substrate drenches on growth of lantana cultivars varying in growth habit.
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