The 2009 ASHS Annual Conference

Native plant growers have been trying to introduce Shepherdia rotundifolia for use in low-water urban landscapes.  Limited seed availability, difficulty with seed germination, and sensitivity to over-watering are problems that obstruct plant growers from success.  The objective of this study was to evaluate strategies for propagation of S. rotundifolia from softwood cuttings.  The experiment was arranged in a randomized strip-plot design with three treatment factors:  inoculation at two levels (inoculated with native soil and non-inoculated), growing medium (calcined clay, peat-perlite [1 sphagnum peat : 1 perlite by vol.]), and an inorganic sand-gravel mix [2 sphagnum peat : 2 perlite : 1 calcined clay : 1 sand by vol.]), and rooting hormone (no hormone, 0.1%, and 0.3%- indole-3-butyric acid [IBA]).  In April 2008, stem bases of S. rotundifolia cuttings from plants growing in their natural habitats were wounded on two sides and moistened before dipping in growth hormone.  Cuttings were held on a propagation bench for 12 weeks under shade cloth and irrigated using intermittent mist.  Mean PAR level beneath the shade cloth was 203 µmol m^-2 s^-1.  The interaction between inoculation and growing media was statistically significant in mean root number (P < 0.0001) and mean total root length (P = 0.009).  Cuttings in calcined clay with no inoculation exhibited the greatest rooting percentage (72%), number of roots (mean 5 roots per cutting), and total root length (mean 9 mm per cutting).  The proportion of cuttings producing callus was greatest (72%) when treated with 0.1% IBA.  Our data suggest that vegetative propagation of S. rotundifolia from softwood cuttings is a viable alternative to seed propagation.  Rooting percent can be increased by using calcined clay as a rooting medium and treating wounded cuttings with 0.1% IBA.