Branch-rooting the weeping willow: Salix babylonica growth rates
Peter R Greene
Weeping Willow (Salix babylonica) growth rates are quantified in terms of tree height, trunk diameter at base, leaf stem length, and root system expansion. Experimentally, these rates are found to be the same for the parent and replanted cutting – in other words, “like father, like son”. Leaf stem growth is stimulated by gravity induced tensile stress, whereas root system growth is stimulated by compressive stress ahead of the root tip. These results may be applicable to the concept of mechanosensing. The aim of this study is regenerating the Salix babylonicae (Weeping Willow Trees) rapidly from branch cuttings. The results indicate that the success rate for replanting the entire willow tree is 75% [68% CI: 54% to 96% (N=4)]. The leaf stem and root system growth rates differ by a factor of 50 or more, but are observed to be the same, 16 ft/yr (5.0 m/yr) and 3.0 in/yr (6 - 7 cm/yr) respectively, both for the branch cutting, and the tree. The conclusion is that the the success rate of propagating branch cuttings, i.e. “branch rooting”, is 25% [68% CI: 15% to 40% (N=8)], similar values are reported by others. This may require branch diameters from 0.6 cm to 1.6 cm.