Allamanda, also known as Yellow Bell or Golden Trumpet, is a genus of tropical shrubs or vines with hairy seeds, native to South and Central America. Their year-round production of large, bright flowers have made the Allamanda popular ornamentals. Allamanda belongs to the dogbane family (Apocynaceae).Usually woody, evergreen shrubs with vigorous growth, Allamanda may reach a free-standing height of 2 metres or more. The leathery leaves are lancelike, pointed, and may either be opposite or in whorls of three or four. The yellow, trumpet-shaped flowers are 5-7.5 cm in diameter; cultivated forms have been selected for larger flowers which may also be white, purple, pink or orange in colour. Their scent may be described as delicate and fruity.
In the wild, Allamanda grow along riverbanks and other open, sunny areas with adequate rainfall and perpetually moist substrate. The plants do not tolerate shade, nor do they tolerate salty or alkaline soils; they are highly sensitive to frost. Allamanda are otherwise undemanding and with appropriate conditions will grow rapidly, from 1-3 metres annually. The seed capsules are oval and prickly; cultivated forms rarely produce seeds, but Allamanda are easily propagated from cuttings. Discarded cuttings are quick to take root.
Allamanda have become naturalized throughout the tropics; they may be seen in roadside ditches, abandoned yards and dumps. As a controlling measure, cutting is ineffecive with Allamanda and will lead to vigorous coppicing. Owing to its fast growth, Allamanda has been introduced widely where it is used as a groundcover or for hedges and screens. In some areas Allamanda are an invasive species, notably Allamanda cathartica in Queensland, Australia.
Allamanda cathartica from Costa Rica
Allamanda cathartica from Costa Rica
Allamanda cathartica is also notable for its medicinal properties: all parts of the plant contain allamandin, a toxic iridoid lactone. The leaves, roots and flowers may be used in the preparation of a powerful cathartic (hence the name); the milky sap is also known to possess antibacterial and possibly anticancer properties. Gardeners exposed to the sap will develop rashes, itch, and blisters.
