Birdsfoot trefoil is a perennial weed, which has a low mat-forming growth habit. The leaves of birdsfoot trefoil alternate on the stems, forming in a trifoliolate pattern, but containing two leaflets at the base of the leaf. The leaves are oblanceolate in shape and usually have smooth edges. The stems of birdsfoot trefoil are square at the top and round at the base. Birdsfoot trefoil has a taproot and develops rhizomes and stolons. The flower of birdsfoot trefoil is yellow and forms in the typical legume shape. The plant flowers in late spring and blooms throughout the summer. The seed pod is cylindrical and shaped like a birds foot. Birdsfoot trefoil usually spreads by seed that germinates in the spring, but can also spread by rhizomes and stolons to form dense patches. The top of the plant browns with frost in the fall and will die back to ground level. Birdsfoot trefoil is often confused with large hop clover. Birdsfoot trefoil is found from Newfoundland and Minnesota south to Virginia, west through Nebraska and Kansas.
Birdsfoot trefoil is often used to stabilize soil or as a forage crop, but it escapes onto roadsides, turf areas and waste sites. It tolerates a wide range of soil types and moisture conditions. It tolerates drought very well. It can be an indicator of low fertility. Cultural control is best achieved by having a well-fertilized actively growing turf. This would include not allowing the turf to become drought stressed.
For optimum control of birdsfoot trefoil, make your post-emergence herbicide application in the spring when plants are young and actively growing. Very densely matted plants may require a repeat application.