Growth boxes were used in a greenhouse to evaluate aboveground and belowground growth, and biomass allocation in seedlings of Acacia farnesiana and Celtis laevigata in infertile and fertile soils. Acacia farnesiana is a N-fixing, heliophyte, which is a dominant in mesic, early successional communities in some areas of the southern United States and northern Mexico. Celtis laevigata is a sciophyte, which assumes dominance as many of these communities mature. Length of stem, length of root, number of leaves, and basal diameter of seedlings of A. farnesiana were significantly greater than those of C. laevigata, regardless of nutrient level. Both species showed increased length of stem, length of root, and number of leaves when nutrients were added; however, the amount of increase in length of root depended on species. Shoot, root, and total dry mass of seedlings of A. farnesiana was significantly greater than in C. laevigata. Addition of nutrients increased dry masses of both species. Additions of nutrients had no effect on root:shoot allocation of either species; however, root:shoot ratios were greater in C. laevigata than for A. farnesiana. Data suggest that for the late-successional species C. laevigata to establish in the successional sequence, some factor other than nutrients, such as light levels, must inhibit the continued establishment of seedlings of A. farnesiana.