Based on an herbarium survey, clover broomrape (Orobanche minor J. E. Smith) was found to have an 116 yr history in the United States. It has been collected 98 times in a total of 32 counties in 12 states and the District of Columbia, and it appears to have become established in seaports and along railroads. It most commonly parasitizes red and white clover, but also burley tobacco, carrots, and several species of ornamental shrubs and herbs. Distribution of clover broomrape indicates either a pattern of repeated introductions from foreign sources, or a persistence in areas where the parasite has become established. While not presently a significant threat, the potential for damage to crops of economic importance cannot be ruled out. The flowers are autogamous.
