Propagation of Several New England Shrubs by Softwood or Semi-hardwood Stem Cuttings

Many shrubs indigenous to New England remain absent from the horticulture industry despite traits that make them attractive for cultivation.  As part of a project to evaluate indigenous plants for horticultural potential, we evaluated adventitious root development on softwood stem cuttings of Myrica gale and semi-hardwood stem cuttings of Rhododendron canadense, Lonicera villosa, and Ilex mucronata treated with auxin in the form of K-IBA dissolved in water or IBA dissolved in 50% ethanol.  Cuttings of each taxon were evaluated for rooting percentage after a minimum of five weeks under mist.  Ninety-five percent of M. gale cuttings rooted when auxin was not applied, and auxin concentrations higher than 1000 ppm reduced root formation.  Rooting percentages ranged from 20-50% among cuttings treated with 3000-10,000 ppm IBA or K-IBA.  Nearly all cuttings of R. canadense rooted, whether auxin was applied or not.  Cuttings produced dense profusions of adventitious roots that were thinner and shorter than adventitious roots produced by many other taxa.  One hundred percent of L. villosa cuttings rooted without auxin treatment, as well as when IBA or K-IBA was applied at 1000, 3000, or 5000 ppm.  Cuttings of I. mucronata rooted poorly, although auxin concentrations of 1000-10,000 ppm produced rooting in 20-30% of cuttings, whereas no rooting occurred without exogenous auxin.  Our results demonstrate that L. villosa, R. canadense, and M. gale are readily propagated from stem cuttings, and that higher auxin concentrations or factors other than auxin need to be evaluated for commercial propagation of I. mucronata.