Development of a vegetative propagation protocol for Asclepias tuberosa

Abstract

This article describes the first published report of a commercially viable vegetative propagation protocol for butterfly milkweed (Asclepias tuberosa L. [Apocynaceae]). Milkweed (Asclepias L.) species are regarded as a superior North American native pollinator taxa. Restoration of species into disturbed sites and increasing its use in managed landscape environments are a means of sustaining and promoting many threatened and endangered pollinators that rely on Asclepias spp. for nectar in the adult stage and for forage in the juvenile stage of development. Unlike restoration efforts that predominantly rely on seed-produced plants, commercial ornamental production relies heavily on vegetative propagation. However, vegetative propagation of Asclepias spp. on a commercial scale has been limited due to the lack of published propagation protocol(s). This study employed vegetative cuttings of Asclepias tuberosa taken at 2 maturities and treated with potassium salt of indole-3-butyric acid (K-IBA) or 1-naphthaleneacetic acid (NAA) at varying concentrations to determine if a commercially viable protocol could be developed. Comparing cuttings taken from container-grown mature stock plants and juvenile seedlings, propagules originating from mature plants resulted in higher survival, likely because of enhanced carbohydrate reserves and photosynthetic capacity. Exogenous auxin (K-IBA or NAA) treatments had no effect on cutting survival or root number and length. The only growth parameter influenced by a specific hormone and concentration was cutting height, which was greater when K-IBA at 1000 or 3000 ppm concentrations were employed, compared to the control with no hormone applied. Ultimately, vegetative propagation can be achieved with commercially acceptable success using no exogenous hormone application.