Benzyladenine Affects Branching and Rooting of Herbaceous Perennial Plugs

To increase branching early in plant development, benzyladenine (BA) was applied as a foliar spray to Agastache 'Purple Haze’, Gaura lindheimeri 'Siskiyou Pink', Lavandula x intermedia 'Provence', Leucanthemum x superbum 'Snowcap', and Salvia nemorosa 'May Night'. After rooting but prior to transplant, plugs were treated with BA at 0 mg·L^-1, 300 mg·L^-1 (applied once or twice), or 600 mg·L^-1. Shoot and root growth were evaluated at 0, 2 and 3 or 4 weeks after treatment (WAT), as well as after transplant and growing out (finished, 8 WAT). Results varied by crop, but all plugs showed a 20% to 100% increase in branching at 3 or 4 weeks after BA treatment. BA-treated Agastache plants showed a 40% increase in the number of branches but a 40% decrease in root dry weights compared to controls at 3 WAT. Finished Agastache plants (8 WAT) had 25% fewer branches and leaders at the two highest BA rates as compared to control plants. Treated Gaura had a 40% to 80% increase in the number of shoots and a 20% increase in lateral branches with no affect on root dry weight at 4 WAT. Finished Gaura plants treated with BA had 80% more shoots and branches as compared to controls. Treated Lavender had a 40% to 100% increase in shoots and a 20% increase in lateral branches (at the highest two rates only) at 4 WAT. Lavender plants treated with two applications of 300 mg·L^-1 BA had reduced root dry weights when compared with controls, but this rate also resulted in the highest number of shoots and branches on the finished plants (8 WAT). At 4 WAT, Leucanthemum plants treated with BA had double the number of basal branches and 25% to 40% reductions in root dry weight, but finished plants were not affected by BA. In Salvia plants treated with one or two applications of 300 mg·L^-1 BA,  basal branching increased 40%, with no effect on root weight at 4WAT, and no effect on finished plants. Root surface area and length were highly correlated with root dry weight. Treating plants with BA prior to transplant resulted in more branching in plugs. Some reduction in rooting was noted but did not affect the quality of finished plants. After transplant and growing out, branching was increased in two crops, unaffected in two crops and decreased in one crop.