Foliar leachates and extracts from partially decomposed leaves of nine of the most abundant herbaceous and shrubby understory associates in the Lower Coastal Plain flatwoods were tested for their allelopathic effects on germination, radicle extension, and shoot growth of slash pine (Pinus elliottii) and loblolly pine (P. taeda). Foliar leachates from dogfennel (Eupatorium capillifolium) significantly reduced germination of both slash and loblolly pines. Extracts from ruptured leaf cells of dogfennel and fetterbush (Lyonia lucida) strongly inhibited germination and radicle extension in both pine species. Mild inhibition of germination was observed in extracts of four other species tested. Growth of 1-year-old slash pine was reduced on prepared sites if the seedlings were planted within 0.5 m of residual fetterbush debris. Forest Sci. 28:509-515.