Lantana (Lantana camara) is a popular annual bedding plant among consumers because it is heat tolerant and attracts pollinators with its vibrant and often multi-colored flowers. Greenhouse growers commonly apply plant growth regulators (PGRs) to control lantana growth and produce a compact, well-branched, and flower. Introduction of new lantana cultivars instigates review of previously known PGR recommendations. As such, the objective of this study was to evaluate the effectiveness of multiple foliar spray applications of ethephon [(2-chloroethyl) phosphonic acid] to control growth and stimulate branching of lantana ‘Bandana Red’. Unrooted cuttings of lantana were received from a commercial propagator and stuck into 105-cell plug trays (30-mL individual cell) filled with a propagation mix. Cuttings were propagated for 35 d under 23 °C air temperature, 24 °C root-zone heating, and a daily light integral of 12 mol·m–2·s–1. Rooted liners were transplanted into individual containers (11.4-cm; 600 mL) filled with a commercial peat-based substrate. Beginning 7 d after transplant, eight single-plant replicants received 1 to 3 foliar spray applications on a weekly basis containing 0 (control; deionized water), 250, 500 or 750 mg·L–1 ethephon. Plants were grown in a glass-glazed greenhouse at 20 °C under ambient daylight supplemented with a photosynthetic photon flux density of ≈125 µmol·m–2·s–1 delivered from LED arrays from 0600 to 2200 HR (16-h photoperiod) to achieve a daily light integral of 12 mol·m–2·d–1. At 42 d after transplant, plants were destructively harvested, and data collected. In general, multiple foliar spray applications with increasing ethephon concentrations affected lantana plant height, diameter, branch number, and shoot dry weight to different magnitudes. For example, lantana plant height was suppressed by 21% to 39% (12.7 to 9.7 cm) from 250 to 750 mg·L–1 ethephon, respectively, compared to untreated plants and were more compact as applications increased. Plant diameter decreased by 13% to 19% (25.5 to 23.7cm) compared to untreated plants as concentration increased from 250 to 750 mg·L–1, respectively, and as spray applications increased. A similar trend was observed for branch number and shoot dry weight. Overall, multiple foliar spray applications of 250 to 750 mg·L–1 ethephon can control the growth of lantana ‘Bandana Red’; however, growers will need to conduct in-house trials to evaluate the level of control desired. Further studies investigating the effects of multiple foliar spray applications with increasing concentrations of ethephon on additional lantana cultivars are warranted.
