Winter Stem Cutting Propagation of ‘Dwarf Burford’ Holly without Use of a Conventional Auxin Treatment

Abstract

‘Dwarf Burford’ holly (Ilex cornuta ‘Dwarf Burford’) is a significant nursery crop and is widely used in landscapes in U.S. Department of Agriculture hardiness zones 7 to 9. Stem cuttings can be rooted at multiple times during the year, provided cutting wood is sufficiently mature, with auxin treatments traditionally used to encourage rooting. This study was conducted to determine if auxin treatment could be eliminated, thus reducing labor and chemical requirements in the cutting propagation process. In three experiments, terminal stem cuttings of ‘Dwarf Burford’ holly were taken in winter, prepared with and without use of a basal quick-dip in an auxin solution, and rooted in a warm, high-humidity environment. Rooting percentages for nontreated cuttings and cuttings treated with 2500 ppm indole-3-butyric acid (IBA) + 1250 ppm 1-naphthaleneacetic acid (NAA) were similar, while treatment of cuttings with 5000 ppm IBA + 2500 ppm NAA resulted in a decrease in rooting percentage. The number of primary roots and total root length were similar among the three treatments, except in one experiment where total root length was greater with auxin-treated cuttings than with nontreated cuttings. Initial shoot growth responses were variable among the three experiments. The treatment of cuttings with auxin was not required for successful rooting and can be eliminated from the process for winter stem cutting propagation of ‘Dwarf Burford’ holly.