The Cactoideae are the largest subfamily of the cactus family, Cactaceae. The plants are highly variable in habit, treelike, shrubby, caespitose, climbing, or epiphytic, from 1 cm to 20 m high. Reproductive zones are usually undifferentiated, sometimes differentiated, or specific cephalium produced. Leaves are absent or rarely vestigial. Glochids are absent. Spines are usually present or rarely absent. Flowers are sessile, diurnal, or nocturnal, 1 - 30 cm in diameter, white, yellow, orange, red, purple, pink, or brown. Blue-coloured flowers are absent. Fruits are usually fresh and berry-like, and the seeds are small, 0.1 - 2.0 mm in size.