Oxalis tetraphylla is a bulb

Bulb

A bulb is a short stem with fleshy leaves or leaf bases. The leaves often function as food storage organs during dormancy.A bulb's leaf bases, known as scales, generally do not support leaves, but contain food reserves to enable the plant to survive adverse conditions. At the center of the bulb is...

ous plant from Mexico. A common name is "Iron Cross

Iron Cross

The Iron Cross is a cross symbol typically in black with a white or silver outline that originated after 1219 when the Kingdom of Jerusalem granted the Teutonic Order the right to combine the Teutonic Black Cross placed above a silver Cross of Jerusalem....

", after a famous cultivar

Cultivar

A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...

; it is also known as "lucky clover", and in a wild or feral

Feral

A feral organism is one that has changed from being domesticated to being wild or untamed. In the case of plants it is a movement from cultivated to uncultivated or controlled to volunteer. The introduction of feral animals or plants to their non-native regions, like any introduced species, may...

 state as Four-leaf Sorrel

Sorrel

Common sorrel or garden sorrel , often simply called sorrel, is a perennial herb that is cultivated as a garden herb or leaf vegetable...

or, least ambiguously, Four-leaved Pink-sorrel.

It has leaves divided into four and has been called "lucky leaf" and even "four-leaf clover", but it is not a true clover

Clover

Clover , or trefoil, is a genus of about 300 species of plants in the leguminous pea family Fabaceae. The genus has a cosmopolitan distribution; the highest diversity is found in the temperate Northern Hemisphere, but many species also occur in South America and Africa, including at high altitudes...

. Related to the Common Wood-sorrel (O. acetosella), it is commonly used as an ornamental plant

Ornamental plant

Ornamental plants are plants that are grown for decorative purposes in gardens and landscape design projects, as house plants, for cut flowers and specimen display...

. It is also edible, the flowers and leaves having a sharp lemon

Lemon

The lemon is both a small evergreen tree native to Asia, and the tree's ellipsoidal yellow fruit. The fruit is used for culinary and non-culinary purposes throughout the world – primarily for its juice, though the pulp and rind are also used, mainly in cooking and baking...

 flavor. However, since the oxalic acid

Oxalic acid

Oxalic acid is an organic compound with the formula H2C2O4. This colourless solid is a dicarboxylic acid. In terms of acid strength, it is about 3,000 times stronger than acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate , is a chelating agent for metal cations...

 in the plant can interfere with the absorption of certain nutrients in the body, especially calcium

Calcium

Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

, too much can be harmful.

If planted in early spring it will grow and flower throughout spring and summer. Some bulbs can survive a cold winter but in areas with frost they should be kept in a cool dry place over winter and replanted in the spring. The bulbs will multiply by autumn.