A small, creeping herb with clover-like leaves that have a sharp, sour, lemon-like flavour due to oxalic acid. They can be used sparingly in salads, sauces and as a garnish. It is smaller than the native sorrel (Oxalis magellanica). The small, yellow flowers appear in summer. It grows in damp, shaded forest throughout New Zealand. The leaves are divided into three heart-shaped leaflets, similar to clover. They are bright green and sometimes have purple markings underneath. The sour flavour comes from oxalic acid, which is also found in spinach and rhubarb. The leaves should be eaten in moderation, as large amounts of oxalic acid can interfere with calcium absorption. The flowers are small and yellow, with five petals. They appear in summer and are followed by small, capsule-like fruits that contain the seeds. The seeds are dispersed by ants, which are attracted to a fatty structure on the seed coat. Native wood sorrel is a plant of the damp forest understorey. It grows in shaded, moist sites, often on the banks of streams or in the shelter of larger plants. It forms small colonies, never becoming aggressive or weedy. To find native wood sorrel is to walk the damp forest floor. Look for the small, clover-like leaves, the yellow flowers. Taste a leaf and feel the sour tang. It is a small plant, but it has a big flavour. A few leaves can add a lemon-like brightness to a salad or a sauce. It is the wood sorrel of the forest, the sour of the shade.