From Elements of Botany:
"Zanthorhjza apiifolia, commonly called Yellow-root. This fine shrub is a native of North-Carolina, and other southern parts of the United States. The root and the wood furnish a fine, but not lasting, yellow dye. They are also very bitter, and nearly allied to the Columbo, but less pure."
This plant is now known as Xanthorhiza simplicissima.