Abstract

A study was conducted to determine if there were synergistic effects from applying two plant growth regulators (PGRs), cyclanilide (CYC) and benzyladenine (BA), with cytokinin properties on Rhaphiolepis sp. (L.) Lindl. ‘Conor’ and ‘Snow White’ (Indian hawthorn), Rhododendron L. ‘North Lake Beauty’ (azalea), and Ilex crenata Thunb. ‘Sky Pencil’ (Japanese holly) during nursery production. Foliar applications of 100 or 200 ppm CYC promoted new shoot development in all species, whereas 2500 ppm BA either had no effect or suppressed shoot development, except in one of two experiments when shoot development was promoted in holly. With no species was there a synergistic effect on shoot development from combining the two PGRs, even when both PGRs individually promoted new shoot development in holly. Indian hawthorn and holly developed transient symptoms of toxicity in response to CYC, BA, and CYC + BA combinations that had dissipated by the end of the growing season and had no lasting effects on plant quality.