Capers are the unopened flower buds of a straggling spiny shrub, Capparis spinosa, in the family Capparaceae. This plant has been known for millennia and is cultivated in the Mediterranean region. Capers grow wild in the Mediterranean region as well as in North Africa and from Turkey west to the Gobi Desert. The buds are pickled in vinegar and used as a condiment; they are also often included in sauces (e.g., tartar sauce) and as a seasoning with raw meat (e.g., steak tartare). The plant has thick leaves, each with a pair of spines at its base. The white or pinkish flowers are 4 to 6 cm across.
(Vaughan and Geissler 1997)