This ubiquitous European import grows almost anywhere the grass isn’t mowed too frequently. It keeps blooming throughout the season: this flower was going strong in early November in Beechview. It came to America as a pasture crop, and soon found that it really liked our open spaces.

Gray describes the genus and the species:

TRIFOLIUM [Tourn.] L. CLOVER. TREFOIL
Calyx persistent, 5-cleft, the teeth usually bristle-form. Corolla mostly withering or persistent; the claws of all the petals, or of all except the oblong or ovate standard, more or less united below with the stamen-tube; keel short and obtuse. Tenth stamen more or less separate. Pods small and membranous, often included in the calyx, 1-6-seeded, indehiscent, or opening by one of the sutures. Tufted or diffuse herbs. Leaves mostly palmately (sometimes pinnately) 3-foliolate; leaflets usually toothed. Stipules united with the petiole. Flowers in heads or spikes. (Name from tres, three, and folium, a leaf.)

T. PRATENSE L. (RED C.) Perennial; stems ascending, somewhat hairy; leaflets oval or obovate, often notched at the end and marked on the upper side with a pale spot; stipules broad, bristle-pointed; heads ovoid, sessile or not rarely pedunculate; corolla magenta to whitish; calyx soft-hairy. Fields and meadows; extensively cultivated. (Introd. from Eu.)