Previous spelling as "trifolium" is generally considered incorrect (W). This monotypic genus is widespread in northeastern and Appalachian regions ( W). In Ky. it is generally restricted to mesic woods on lower slopes and terraces with medium acid, sandy soils. The coll. from CAMP (EKY) has dubious data, just "Newport... May 1970".Although the plant locally forms large populations (probably with through clonal divisions), it has a highly fragmented distribution in the state, suggesting great sensitivity to past disturbance (such as rooting by hogs). N. trifolius differs from P. quinquefolius in several fundamental characters (Philbrick 1983; Cr, W and cited literature). It has short rhizomes that are attached to globose roots (versus no rhizomes and fusiform roots); leaves are smaller, ca. 4-8 x 0.5-2.5 cm (versus 6-15 x 3.5-7 cm) and less divided, with 3 or rarely 5 leaflets (versus 5 or rarey 3), petiolules 0-3 mm (versus 7-25 mm) amd apex obtuse to acute (versus acuminae); inflorescence are ndding in bud (versus erect); flowers are androdioecious (versus monoecious), with white or pinkish petals (versus light green); ripe berries are yellow-green (versus bright red); 2n = 24 (as in most native Araliaceae) versus 48.