Benzyladenine Increases Branching but Reduces Root Growth of Herbaceous Perennial Liners

Abstract

The objective of this study is to evaluate the branching effect of benzyladenine (BA) on herbaceous perennial plants during the production of rooted cuttings (liners) and to examine and quantify the root growth of these liners using multiple methods of root evaluation. Five crops were studied: Agastache Clayt. Ex Gronov. ‘Purple Haze’, Gaura lindheimeri Engelm. & A. Gray ‘Siskiyou Pink’, Lavandula ×intermedia Emeric ex Loisel. ‘Provence’, Leucanthemum ×superbum (Bergmans ex J.W. Ingram) Bergmans ex Kent. ‘Snowcap’, and Salvia ×sylvestris L. (pro sp.) ‘May Night’. After rooting but before transplant, BA was applied to rooted cuttings as four treatments: controls (0 mg·L−1), one application of 300 mg·L−1, two applications of 300 mg·L−1, or one application of 600 mg·L−1. Results varied by crop; all crops except Salvia had increased branching as measured as either increased lateral or basal branches and/or increased leaders at 3 to 4 weeks after initial treatment. Four crops showed reduced root growth, whereas Gaura was unaffected. Root dry weight was found to be highly correlated with root surface area and root volume. After transplant and growing out, branching of the finished plants was increased in Gaura and Lavandula, unaffected in Salvia and Leucanthemum, and decreased in Agastache. Treating rooted cuttings with BA before transplant increased branching but the effects were not long lasting, which suggests that additional applications at or after transplant may improve finished plant quality. Reductions in root growth noted in rooted cuttings did not affect the growth of finished plants. Chemical names: N-(phenylmethyl)-1H-purine-6-amine (benzyladenine, BA).