Cutting-propagated ‘Alice’ oakleaf hydrangea (Hydrangea quercifolia Bartr.) often produces a few vigorous branches with apical dominance, thus suppressing growth of other branches. As a result, the maturing canopy is sparse and develops asymmetrically, rendering plants unappealing to customers. For this reason, growers prune or apply plant growth regulators (PGRs) to encourage more branching, thereby producing a more desirable product. Propagation through tissue culture may provide another option to increase branching as an outcome of habituation. Habituation occurs when plant cultures continue to respond to a hormone that is no longer being supplied and, in turn, frequently leads to more branching. We evaluated oakleaf hydrangea growth as affected by propagation technique [tissue-cultured (TC) and cutting-propagated (CUT)] and PGR (cyclanilide and benzyladenine) application during container production. Nontreated TC plants had more branches longer than 15.2 cm (6 in) compared to nontreated CUT plants in 2008, although not in 2010. In both years, single applications of cyclanilide did not affect total branch number but two applications increased total branch number compared to nontreated plants, averaged over propagation technique. Plants treated with benzyladenine had similar or fewer total branches compared with nontreated, hand-pruned, and cyclanilide-treated plants (one or two treatments). Propagation technique did not consistently influence response to PGRs.
Growth regulators and carving on breakage of apical dominance in tannia [Xanthosoma sagittifolium (L.) Schott] rhizomes