Abstract

Stem cuttings of Lindera umbellata Thunb. (Chinese spicebush) were taken on three dates representing three growth stages (softwood, semi-hardwood, or hardwood). Semi-hardwood and hardwood cuttings were treated with 0, 2500 (0.25%), 5000 (0.5%), 7500 (0.75%), or 10,000 (1.0%) ppm of the free acid of indolebutyric acid (IBA) dissolved in 50% isopropyl alcohol, whereas softwood cuttings were treated with the same concentrations of the potassium (K) salt of IBA (K-IBA) dissolved in distilled water. All cuttings were placed in a raised greenhouse bench and rooted under intermittent mist. After 12 weeks, the cuttings were harvested and various data recorded. The majority of the hardwood cuttings died, with none of the survivors rooting. Softwood cuttings survived but with overall rooting of only 5%. Response of the semi-hardwood cuttings to IBA was quadratic with the greatest rooting (73%) observed for those cuttings treated with 7500 ppm IBA. However, root number and root length were not significantly affected by IBA treatment. Sixty of the rooted semi-hardwood cuttings were potted and later provided with overwinter protection in an unheated greenhouse but only three of these cuttings were alive by the following summer.