Germination and propagation of Astragalus michauxii, a rare southeastern US endemic legume

Abstract

The US Department of Defense is taking proactive steps to conserve rare species that occur primarily on lands under its stewardship, including Astragalus michauxii (Kuntze) F.J. Herm. (Sandhills milkvetch; Fabaceae). We completed a series of evaluations to determine effective means of germinating and propagating A. michauxii. We collected A. michauxii seed from Fort Bragg, an Army Installation located in the Sandhills ecoregion of North Carolina. While previous work described a germination protocol and suggested the presence of chemical dormancy, we determined that A. michauxii possesses only physical dormancy, which can be successfully broken by mechanical scarification yielding a > 94% germination rate. We also developed an effective method for large-scale propagation of A. michauxii by directly sowing seed into media, rather than transplanting seedlings from Petri plates. This method resulted in an emergence rate comparable to the observed germination rate and a 69% survivorship of seedlings ex situ. Our simplified germination and propagation protocols can effectively be used to provide individual plants for use in reintroduction and restoration.