Because it is a warm-season legume, birdsfoot trefoil makes an ideal companion species for Kentucky bluegrass in permanent pastures. Bluegrass, a cool-season grass, grows most vigorously in spring and fall, while trefoil grows best in late spring and summer. This fact must be kept in mind if trefoil is to persist in bluegrass sod. Heavy grazing of the bluegrass is required in early spring in order to prevent the later-emerging trefoil plants from being shaded out. Shading is more damaging to trefoil than to other legumes.
Trefoil is adaptable to a wide range of soils that vary in acidity, fertility and drainage.
But it still needs adequate liming and fertilizing for maximum production. As already mentioned, birdsfoot trefoil is difficult to establish. This is because the seedlings lack vigor and, therefore, do not compete against a companion crop, weeds or grasses as well as other forage legumes. Adequate lime and fertilizer. Proper seedbed preparation.