Red clover is an extensively grown perennial, alone or in combination with grasses for hay and pasture in the northeastern, north-central, and southeastern United States. In the Pacific Northwest it is grown under irrigation  or in areas with good drainage and soil moisture. It is an introduced species. Native to north Atlantic and central Europe, the Mediterranean region, Balkans, Asia Minor, Iran, India, Himalayas, Russia from Arctic south to east Siberia.  It spread to England ca 1650 and was carried to America by British colonists (Taylor and Smith, 1981).

Leaves are palmately trifoliolate; leaflets not serrated; inverted V-shaped "water mark" usually present; large stipules; stems leaves and petioles pubescent.
Flower heads consist of up to 125 flowers; rose purple or deep purplish-red; heads nested in 2-3 leaves.
HERE is an excellent page from Purdue University - everything you need to know about red clover.