Oxalis acetosella
 Oxalis corniculata

Oxalis

(Oxalidáceae) wood sorrel

The 8 genera of the family of the wood sorrels, including approx. 900 sorts, grow in the tropics; they are especially high in biodiversity on the southern hemisphere from where they spread to the adjacent southern and northern regions with temperate climate. They include herbs, half-shrubs, or rarely even trees with bulbs, rootstocks (a subterranean shoot) or nodules. Mostly, the plants are marked by finger-like pinnate leaves which can often carry out movements due to stimuli. Furthermore, the plants have glandular hair and lysigenous gaps for secretion. The blooms with five petals are mostly combined in inflorescences which comprise a leaf axil. Sometimes they are one single bloom. The stamens can be found in a group of ten, mostly in 2 circles, and are assembled in a ring-like way at the stem. The longer stamens often carry appendixes which look like little teeth. The ovary is grown together out of 3 or 5 carpels. It has a head-shaped stigma and includes according to the drawers 2 to numerous seed pods. The fruits are mostly capsules which burst open their drawers, often with additional devices for hurling out the seeds. Sometimes there are also fleshy berries in that family.

The genus "averrhoa" is cultivated as a useful plant in the entire tropics. These are small trees with pinnate leaves. This genus is also known for moving the leaves during sleep. The compound leaves react to stimuli by touches. In that situation the compound leaves are folded up in a downward direction.

"Averrhoa carambola" is a very sour-tasting, aromatic fruit, with a 5-pointed shape, which can be used to make compote or fruit juice.

"Averrhoa bilimbi" has cucumber-like fruits which are as long as a finger. They taste sour and can be used as compote or vegetables.

The genus "biophytum" includes some 70 sorts of low, partly stringy plants and is found in the entire tropics apart from Polynesia.
These plants usually have yellow blooms and are assembled in inflorescences which look like heads or umbels. Biophytum sensitivum is up to 10cm in height. It can easily become a dangerous weed and is also found in green houses. This plant reacts strongly to stimuli due to shock and sore.

 The main genus of the family is "oxalis", wood sorrel, which has some 800 sorts. The genus owes its name to the embedded calciumoxalate-crystals (oxalic acid).

The plants of this genus really grow everywhere on our planet. Especially rich in genera are the Andes, the tropical regions of Brazil, Mexico and South Africa.

In this group are both annual plants and perennial shrubs. The oxalis plants are not of any economic significance. In former times, oxalis acetosella was used in the Black Forest to produce out of a weight of 75 kg leaves and amount of 500 g oxalic acid for technical purposes.

The cloverleaf is also born as the heraldic emblem on the Irish coat of arms. It used to be eaten as salad or side dish due to its somewhat sour taste. People living in the Andes eat the root tubercules and the oxalis tuberosa's stems which are above ground. These large tubercules which are rich in starch are a called "oca" and still represent a very important basic food of the population there. We mistakenly call oxalis deppei "four-leaved clover" as it actually has four leaves like ours. This sort, originating from Mexico, was imported in 1822 and belongs to the sorts which are not hardy. Those bulbs that have been propagated by means of a complicated procedure are designed for being sold in October. 95% of these ornamental plants sold are put up to sale during the weeks before Christmas and the days before New Year.