Cyclanilide Promotes Branching of Woody Ornamentals

Abstract

Woody ornamental shrub production often requires multiple prunings to promote branching and compaction. Pruning, a labor-intensive practice that results in a loss of plant biomass, often lengthens production time but is considered essential to develop attractive, marketable shrubs. The effects of cyclanilide (CYC), a relatively new bioregulator recently made available for testing, were evaluated as a means of lessening or eliminating the mechanical pruning of select woody ornamental shrubs. Single foliar sprays of 25 to 200 ppm CYC increased branching and enhanced overall quality of 12 of 19 tested species of woody landscape shrubs, however CYC-induced effects tended to be short-lived and treated plants often appeared similar to untreated plants by 120 days after treatment. Multiple foliar sprays of 100 to 300 ppm CYC, applied either weekly or biweekly, promoted branching and quality of 5 of 9 woody ornamental shrubs, and CYC effects generally persisted longer than those from single CYC applications. However, increased longevity of plant response was often associated with foliar injury, symptoms of which generally increased in severity with increasing CYC concentrations. Although injury was transient and no longer evident by approximately 120 days after treatment, symptoms were severe enough to discourage multiple foliar applications of CYC concentrations above 100 ppm to ensure plant marketability during the growing season of application. The interaction between pruning and CYC application was evaluated on several woody ornamental shrubs. CYC concentrations of 100 to 200 ppm applied to overwintered nursery crops increased shoot formation, however quality was usually not enhanced, suggesting woody shrubs that have become leggy and misshapen will probably require pruning before CYC application to fully enhance plant form and marketability. Results of another study in which 200 ppm CYC was applied to plants immediately after pruning or when new foliage elongated to either 1.3 – 2.5 cm (0.5 to 1.0 in) or 2.5 – 5.1 cm (1.0 – 2.0 in) suggested that shoot formation is most effectively enhanced when plant foliage is allowed to elongate 1.3 – 5.1 cm (0.5 – 2.0 in).