Effects of Collection Date, Wounding, and Auxin Treatment on Rooting of Amelanchier spicata Propagated By Stem Cuttings

Amelanchier spicata (dwarf serviceberry) is a shrub native to North America with ornamental and agricultural potential. Although other members of the genus may be propagated by stem cuttings, information on the propagation of this species is absent from the literature. Our objective was to evaluate the effects of collection date, wounding, and K-IBA treatment on adventitious rooting of softwood and semi-hardwood cuttings. Cuttings were collected from an indigenous population in Maine on June 18, July 1, July 15, and July 30, 2015. Half of the cuttings were wounded, and all were treated with a quick-dip of water or K-IBA at concentrations of 1000, 3000, and 5000 mg·L^-1. These treatments were selected because a preliminary experiment indicated that K-IBA was effective and concentrations above 5000 mg·L^-1 did not enhance rooting percentage or root quality. Following 61 days under intermittent mist, we recorded the percentage of cuttings producing roots and subjectively rated root systems based on overall quantity and quality of roots. Rooting percentages and root ratings diminished when annual growth transitioned to a semi-hardwood condition, and cuttings collected in late July did not produce roots consistently. Wounding significantly increased rooting percentage and root ratings among all cuttings treated with K-IBA. Among concentrations we evaluated, 5000 mg·L^-1 K-IBA promoted greatest root ratings for each collection time. Although rooting percentages were consistently high (80-100%) for wounded softwood cuttings, root ratings averaged only 2.1 out of five over the first three collection dates. Future work should investigate factors, such as juvenility and increased K-IBA concentration, which might increase the quality of adventitious root systems on stem cuttings of A. spicata.