Common names: Hemp broomrape, branched broomrape
Family: Orobanchaceae (Broom-Rape Family)
Habit: Annual, biennial, or perennial herb, depending mainly on host; stems 10-40 cm tall, swollen at base, attached to host roots, simple or branched, glandular puberulent; leaves reduced to scales, 3-10 mm, ovate to ovate-lanceolate, acute; inflorescence 2-25 cm, lax to moderately dense, glandular pubescent; bracts 6-10 mm, ovate-lanceolate; bracteoles linear-lanceolate, about equalling calyx; pedicels 0-8 mm; entire plant lacking chlorophyll, yellow or yellowish violet; calyx 6-8 mm; corolla 10-22 mm; glandular-pubescent, suberect and inflated at base, white or yellow to violet or bluish, usually pale; filaments inserted 3-6 mm above base of corolla; stigma white, cream or pale blue; capsule 6-10 mm containing numerous dust-like seeds. Plants highly variable where native; less so in introduced populations. A single plant carries ten to several hundred flowers and hence may produce up to a quarter million seeds. The plant is pale, completely lacking any chlorophyll. The base of the stem, below ground, is normally swollen and tuberous.
Problems: Hemp broomrape is a worldwide noxious parasite of many crops and associated weeds. Heavy infestations can severely damage crops. Biology & Spread: Reproduces by seed. Seed disperses with human activities, farm machinery, water, and wind.
History: Orobanche ramosa is native to the Mediterranean area of southern Europe but has been spread to a number of other parts of the world. U.S. habitat includes ornamental and vegetable crop fields, especially tomato fields.
Distribution: Introduced to U.S. Introduced from Europe. Present distribution includes southern Europe (occasionally introduced farther north) to Russia and Siberia. It is also present in northern and southern Africa and the Middle East. In the Americas, O. ramosa has been introduced and is established in the U. S., Mexico, and Cuba. It was reported at one time infesting hemp and tobacco in Kentucky. U.S. Present: CA, IL, KY, NC, NJ, TX
Management: Hand pulling plants, plowing under trap crops before seed production, or burying seed with one deep inversion plowing can help control infestations.