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 color. Their scent may be described as delicate and fruity. 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.