The effect of tall fescue turf on growth, flowering, modulation, and nitrogen fixing potential of Lupinus albifrons Benth. was examined for greenhouse and field grown plants. No allelopathic effect was observed for lupine plants treated with tall fescue leachates. The nitrogen-fixing potential measured by nodule dry weight and acetylene reduction rates was not significantly affected by either tall fescue turf or low nitrogen fertilization. Both the greenhouse and field studies showed that the growth, sexual reproductive allocation, and number of inflorescences were significantly reduced when lupine plants were grown with tall fescue. The root length densities of tall fescue turf and lupine monoculture were measured. The tall fescue turf had 20 times higher root length density (20 cm cm-3 soil) than the lupine plants monoculture. This suggests that intense competition at the root zone may be a dominant factor which limits the growth of the lupine plants. The reproductive characters of the lupine plants was improved by phosphorus fertilization. Transplanting of older lupine plants into the turf substantially alleviated the tall fescue turf competitive effect.