This is largely restricted to southern Appalachian regions, especially in mesic ravines. It is probably widespread in most of Appalachian Ky. but there are remarkably few recent colls. The only records from the Bluegrass region are old colls. (KY-Agr.) from ANDE and FAYE that seem to be valid. The disjunct record from EDMO (McKinney et al. 1990) needs to be confirmed. Astilbe biternata is often confused with Aruncus dioicus (Rosaceae). Both are tall herbs of mesic woods with compound leaves and paniculate inflorescence of small white unisexual flowers). A. biternata is usually dioecious--versus strictly so in Aruncus. Habitats are similar habitat, though Aruncus is somewhat less restricted to mesic sites. A. biternata can be distinguished as follows (FNA 8, W): terminal leaflets 3-lobed (versus 0-2 lobed), glandular (versus nonglandular) hairs on stems and lower leaf surfaces, flowering slightly later, with 10 stamens (versus 15-20), and usually 2-carpellate fruits (versus 3-4).