LACK of seedling vigor is a serious limitation to obtaining adequate Lstands of birdsfoot trefoil (Lotus corniculatus L.). Slow seedling growth makes establishment difficult because competition from weeds or companion crop plants often eliminates the young legume seedlings soon after they emerge. Gist and Mott (4) found that birdsfoot trefoil grows much more slowly than alfalfa and red clover under identical light intensities. Seedlings not eliminated are greatly reduced in size and are susceptible to injury during the winter. Mowing alone has not been adequate for weed control in birdsfoot trefoil plantings when weed grasses are present in the sward. Repeated mowings will control broadleaved weeds, but the growth of the seedling trefoil may be retarded by such treatment. In addition, mowing releases weed grasses from broadleaved weed competition and allows the grasses to compete critically with the legume seedlings. All weed growth must be controlled if most satisfactory trefoil establishment is to be achieved. The aim of this study was to compare several mowing and grasscontrolling herbicide combinations for weed control in birdsfoot trefoil during the year of planting. Also, a handweeding study to evaluate the effects of separate weed components on trefoil development, and a test of the effect of sodium 2,2-dichloropropionate (dalapon) on the nodulation of trefoil are reported.