This is the most common Hop Clover in Illinois. The flowers are bright lemon yellow and reasonably attractive. The other Hop Clovers that occur in Illinois, Trifolium aureum (Yellow Hop Clover) and Trifolium dubium (Small Hop Clover), are similar in appearance, except that the middle leaflets of their trifoliate leaves have petioles that are no longer than the lateral leaflets (they're often sessile, or nearly so). In Low Hop Clover, the petioles of the middle leaflets are conspicuously longer than the others. The common name of these species refers to the persistent flowers, which bend downward with maturity and become light brown or nearly white, causing the flowerheads to resemble the fruiting heads of Humulus spp. (Hops). Another species, Medicago lupulina (Black Medic), has similar flowers and foliage, although its coiled black seedpods are quite different in appearance. If the seedpods are unavailable for examination, it is still possible to distinguish Low Hop Clover from Black Medic by comparing the standards (upper petals) of their flowers. In Low Hop Clover, the outside of the standard (facing upward) has conspicuous grooves along its length, and it is held parallel to the length of the keel (the lower petals). In Black Medic, the standard lacks conspicuous grooves and it is held perpendicular to the length of the keel when the flower is fully open.