Stem cuttings of rose-of-sharon (Hibiscus syriacus L. ‘Jeanne d'Arc’), barberry (Berberis thunbergii DC. ‘Crimson Pygmy’), juniper (Juniperus horizontalis Moench. ‘Plumosa Compacta’), and arborvitae (Thuja occidentalis L. ‘Woodwardii’) were rooted in substrates consisting of 0%, 25%, 50%, 75%, or 100% (by vol) perlite or expanded polystyrene beads with peat. Percentage of rose-of-sharon cuttings rooted and root ratings were lower with polystyrene than with perlite. Statistically, more barberry cuttings rooted with polystyrene (78.8%) than with perlite (78.3%), but the difference in rooting between polystyrene and perlite was not horticulturally significant. More juniper and arborvitae cuttings rooted with 50% perlite than with other perlite concentrations. Percentage of rooted juniper cuttings decreased but percentage of rooted arborvitae cuttings increased as polystyrene concentration in the substrate increased. More roots and longer roots formed on juniper cuttings with perlite than with the same concentration of polystyrene in the substrate. In contrast, arborvitae cuttings had more roots with 25% perlite than with 25% polystyrene, but arborvitae cuttings in 50%, 75%, or 100% polystyrene had more roots than cuttings in the same concentration of perlite. Results indicate expanded polystyrene is a reasonable substitute for perlite in rooting substrate for barberry, juniper, and arborvitae if appropriate ratios of polystyrene to peat are used.
Approved for publication by the Director, Oklahoma Agricultural Experiment Station. This research was supported under project H-2324. The authors appreciate the support of Greenleaf Nursery Co., Park Hill, OK. Technical assistance of Mary Pritchett and Peggy Reed is greatly appreciated. We thank Dr. P.L. Claypool, Department of Statistics, Oklahoma State University for statistical advice.
3Propagation/Research Coordinator, Greenleaf Nursery Company, Park Hill, OK 74451.