Clover broomrape was found in a red clover field in Clackamas County, Oregon in 1998, and has now spread to numerous red clover fields. As of August 2000, the Oregon Department of Agriculture had surveyed 4,280 of the 12,000 acres of red clover production in the state, and had identified 13 fields containing clover broomrape. Clover broomrape threatens the nation's largest red clover seed production industry and may potentially have other hosts that are economically important in Oregon agriculture. The stems are unbranched and yellow to straw-colored.
Leaves are small triangular flaps arranged alternately on the stem.
The roots are short, dark brown, and attached to a host plant. Clover broomrape flowers are borne on the top half of the stem and are off-white to yellow with a purple striping or tint. The flowering period of clover broomrape is very short. Flowering can begin as early as one week after plant emergence, with viable seeds produced within one month of emergence. The seeds are miniscule and plentiful, with production of about 500,000 dust-like seeds per plant.