Cauliflower is one of several vegetables in the species Brassica oleracea in the genus Brassica, which is in the family Brassicaceae. It is an annual plant that reproduces by seed. Typically, only the head is eaten – the edible white flesh sometimes called “curd” (similar appearance to cheese curd). The cauliflower head is composed of a white inflorescence meristem. Cauliflower heads resemble those in broccoli, which differs in having flower buds as the edible portion. Brassica oleracea also includes broccoli, brussels sprouts, cabbage, collard greens, and kale, collectively called “cole” crops, though they are of different cultivar groups.
White cauliflower is the most common color of cauliflower having a contrasting white head (also called “curd”) surrounded by green leaves.
Orange cauliflower (B. oleracea L. var. botrytis) contains beta-carotene as the orange pigment, a provitamin A compound. This orange trait originated from a natural mutant found in a cauliflower field in Canada. Cultivars include ‘Cheddar’ and ‘Orange Bouquet’.
Green cauliflower, of the B. oleracea botrytis group, is sometimes called broccoflower. It is available in the normal curd (head) shape and with a fractal spiral curd called Romanesco broccoli. Both have been commercially available in the U.S. and Europe since the early 1990s. Green-headed varieties include ‘Alverda’, ‘Green Goddess’ and ‘Vorda’. Romanesco varieties include ‘Minaret’ and ‘Veronica’.
The purple color in this cauliflower is caused by the presence anthocyanins, water-soluble pigments that are found in many other plants and plant-based products, such as red cabbage and red wine. Varieties include ‘Graffiti’ and ‘Purple Cape’.
In Great Britain and southern Italy, a broccoli with tiny flower buds is sold as a vegetable under the name “purple cauliflower”; it is not the same as standard cauliflower with a purple head.