Crassocephalum is a genus of flowering plants in the daisy family Asteraceae (order Asterales), native to tropical Africa and widely naturalised across tropical and subtropical regions worldwide. The genus comprises soft, thistle-like annual or perennial herbs that are distinguished from most other composites by their complete lack of ray florets — all flower heads consist solely of disc florets. A characteristic calyculus of short bracts, roughly one-quarter to one-fifth the length of the inner phyllaries, is present on each head. Despite their thistle-like appearance, all parts of the plants are soft and entirely non-spiny.
The genus is closely allied to Senecio, from which it is separated principally by the absence of ray florets. Common names applied to members of the genus include ragleaf, thickhead, and bologi. Several species are cultivated as leaf vegetables, with fleshy and mucilaginous leaves and stems consumed cooked or raw, a practice especially widespread in West Africa. Various parts of the plants have a long history of medicinal use across tropical Africa.
The most widely known member is Crassocephalum crepidioides (Benth.) S.Moore, an erect annual succulent herb that can reach 180 cm in height. It is grown as a food plant across tropical Africa and has spread as a naturalised or invasive weed into other tropical and subtropical regions, including New Caledonia. Like other members of the genus, it contains pyrrolizidine alkaloids — including the hepatotoxic compound jacobine — and the safety of internal consumption warrants caution.
Distribution
Crassocephalum is primarily native to tropical Africa, where several species are cultivated and used as leaf vegetables and medicinal plants. The most widespread species, C. crepidioides, has naturalised across tropical and subtropical regions globally and is considered invasive in New Caledonia.
Ecology
Members of the genus grow as annual or perennial herbs in tropical and subtropical environments. Crassocephalum crepidioides behaves as an opportunistic weed in disturbed habitats outside its native range and has become invasive in parts of the Pacific, including New Caledonia.
Cultural Uses
Several species of Crassocephalum are raised as leaf vegetables, particularly in West Africa, where the fleshy, mucilaginous leaves and stems are eaten as a green vegetable — a practice associated especially with C. crepidioides (known locally as ebolo or bologi). Various parts of the plant have also been used in traditional medicine across tropical Africa. The presence of pyrrolizidine alkaloids, including jacobine, means that the safety of internal medicinal use requires further research.
