Oxalis triangularis is belong to Oxalidaceae family and oxalis genus. Species name is Oxalis triangularis subsp. papilionaceae and cultivar name is atropurpurea. Also Oxalis papilionaceae and Oxalis regnellii are used as synonims. Wood    Sorrel is native to South America; Argentina, Bolivia, Brazil, Paraguay and Peru. It grows naturally amongst rocks near streams.

Oxalis triangularis atropurpurea is an edible, perennial, acaulescent plant, arising from rhizomes, growing to 20 cm tall. The purple leaves, up to 20 cm long, have triangular leaflets that close at night.

Flowers are hermaphrodite pollinated by insects. Sepal apices with a pair of orange tubercles. Petals 15–22 mm, white to pinkish or pale purple. It flowers from April to May occasionally to September. Fruits (capsules) of Wood    Sorrel are  ovoid in shape, 12–18 mm long. Rhizomes are short, branching up to 5 cm long and 15 mm wide. Old ones contain many bulblets at the base.

Oxalis triangularis atropurpurea is grown from seeds or dividing rhizomes or bulbs (including offsets). Division of the bulbils preferred. Like other bulbs, the oxalis go through dormancy periods on a regular basis; at the end of such period, the bulbs can be unearthed, side bulbs cut and replanted in appropriate soil, where they will grow into new plants.

Wood    Sorrel grows in well-drained soil. Suitable both for acid, neutral and basic soils. It adapts in both dry and moist soil. Pot cultivated plants need average potting soil with good drainage preferably in light shade. They require bright or direct sunlight supplemented with a cool indoor temperature of about 15 ºC. They can tolerate higher indoor temperatures but will go into dormancy if temperatures go above 30 ºC for prolonged periods of time. During the active growing season, water  should regularly be given but allow the surface soil to dry out between waterings.

Pruning of the leaves should be done in early summer or during the dormancy period. The plant can tolerates strong winds but not maritime exposure. Fungal leaf spots, powdery mildew, rust, and seed smut are the most common problems, but also watch for spider mites and leaf miners.

Use in Landscape: Wood    Sorrel, is typically grown as a houseplant but can be grown outside if the temperature will not go under -10 ºC. preferably in light shade.

Edible Uses: Leaves of Oxalis triangularis atropurpurea have a pleasant acid flavour and may be eaten raw or cooked. They are a pleasant and decorative addition to the salad bowl. The root is juicy with a pleasant sweet mild flavour and can be eaten raw or cooked. The leaves contain oxalic acid, which gives them their sharp flavour, should not be eaten in large amounts since oxalic acid can bind up the body’s supply of calcium leading to nutritional deficiency. The quantity of oxalic acid will be reduced if the leaves are cooked. People with a tendency to rheumatism, arthritis, gout, kidney stones or hyperacidity should take especial caution if including this plant in their diet since it can aggravate their condition.