The genus Dirca (Thymelaeaceae) comprises three North American species of deciduous understory shrubs. Dirca palustris (eastern leatherwood) occurs in patchy populations in eastern North America. Nevling (1962) reported that D. palustris ranges from New Brunswick west to Minnesota and Oklahoma, and south to Florida. Guided by herbarium records, we recently confirmed the existence of a large population of D. palustris in northern North Dakota, and the persistence of the species in Nova Scotia, as reported by Gray (1873) and more recently by Soper and Heimburger (1994). Throughout its broad range, D. palustris generally occurs infrequently but can be locally abundant (Nevling 1962). It is found in populations of variable densities from few to hundreds of individuals per hectare in rich mesic forests (Schulz et al. 2004), and the species often is associated with north- or east-facing stream banks and slopes (Kurz 1997; Nevling 1962). The two other species in the genus are D. occidentalis, endemic near the San Francisco Bay, and D. mexicana, narrowly endemic to the Sierra Madre Oriental in Tamaulipas, Mexico.