Oxalis tetraphylla

Native from Mexico to Central America, this clump-forming perennial has an underground bulb and a fleshy root that stores reserves. Its leaves usually have four leaflets, rather than the three common in many other wood sorrels, and often bear a purple or dark band. The pink, funnel-shaped flowers have pale greenish throats and are grouped on stalks above the leaves. They close at night and reopen in daylight. The leaves and flowers have a sharp, lemony flavour, but their oxalates can be harmful if large quantities are eaten. The plant can spread vegetatively through small bulbs and slender underground stems. Photographed in Quindío, Colombia.