Oxalis.org / Worldwide Oxalis


	Oxalis is the largest genus in the wood sorrel family, Oxalidaceae. The name is derived from the Greek word, OXYS, or sour and refers to the acidic taste of the foliage. The 800 or so species are cosmopolitan in its distribution and is most abundant in the Southern Hemisphere. Species diversity is particularly rich in South America, Mexico and South Africa. Oxalis consists of annual or perennial plants, mostly herbaceous and shrubby types. The Herbaceous Oxalis has fleshy, scaley and rhizomatous bulbous forms or tuberous root structures. The leaves of most Oxalis usually has three leaflets and are shamrock-like in appearance. But some Oxalis can have anywhere from 1 to 20 unequal, equal, multiple shaped and sized leaflets depending on the species.
The leaves and flowers of some Oxalis are light sensitive at night and tend to close up or fold over. Leaf movements are well known in Oxalidaceae Genus members and also appear to respond to environmental conditions such wind, rain, light intensity and temperature. All Oxalis flowers have five sepals and can come in most colors including white, lavender, pink, purple ,yellow, orange, red and any different combinations there of. Oxalis even have blue flowers in some Mexican species (Denton). Oxalis is remarkable botanically for having different style and stamen positioning, known as heterostyly. Some flowers are long styled, mid styled and short styled. Charles Darwin called attention to this feature in his volume on "the different forms of flowers in plants of the same species". The Oxalis use the different positioning of the styles and stamens to ensure proper fertilization. Some Oxalis flowers never open but pollen can germinate inside the flower and travel down the styles to fertilize its ovules. This is known as cleistogamy. Oxalis are known generally as being weedy, and for good reason. I believe all species of Oxalis could be considered weedy if given the ideal conditions to do so. When the Oxalis' flower is properly fertilized, it forms a fleshy 5-edged seed pod (the fruits) which shoots out numerous seeds at great distances from the mother plant. This propensity, together with its habit of multiplying by forming bulbils either below ground or above ground as detachable bulbs off its stems makes certain that the species carries on from season to season. Some Oxalis spread new bulbs by "runners" which are essentially bulb formation at the end of a root which is connected to the mother bulb and is deposited far away from it. There are two types of Oxalis bulbs. There is the scaly type which is common in American bulbous Oxalis and is known as "Ionoxalis" and the tunicated bulbs which are found in South Africa. The tunicated South African bulbs are divided into six sub types. Dr. Denton in her monograph, notes that the presence of two morphologically distinct bulbs show that the bulbs habit has originated from an unrelated species of the genus. This is certainly open for interpretation and discussion. The tropical and subtropical Oxalis are rarely hardy and its bulbs will not survive harsh winters if left exposed to it. Most though can be easily grown in a sunny cold frame or greenhouse and only require attention from frost. The edible tubers of Oxalis Tuberosa (Oca) have long been cultivated for food in Columbia and elsewhere in the Andes Mountains of South America. The edible leaves of Scurvy-Grass Sorrel, Oxalis Enneaphylla were eaten by sailors off the coast of Argentina and on the Falkland Islands, as a source of Vitamin C to avoid scurvy. Other Oxalidaceae are sources of food, especially in India and China as they produce gooseberry like edible fruit such as Bilimbi and Carambola. A characteristic of many members of this genus is that they contain Oxalic Acid, giving the leaves and flowers a sour taste, some say refreshing to chew in small amounts. However, in large amounts, these species are toxic and interfere with proper digestion. There are reports of sheep poisoning after they ate Oxalis Pes-Caprae in Australia. In the past, it was a practice to extract crystals of calcium oxalate for use in treating diseases and as a salt called "sal acetosella" or "sorrel salt" (aka "salt of lemon") The Oxalic Acid deposits are formed on the sepals, bulb scales, leaves and even the tips of the petals. The presence of Oxalates and tannins apparently protect the plant and its parts from depredation by insects and animals. But mice do like the inner starchy portions of the bulb which tend to have a low concentration of oxalates and tannins. Much of this website deals with the cultivation, propagation and preservation of Oxalis grown as an ornamental plant. Though there are many sites that describe how to get rid of these horrid weeds, such as Oxalis Corniculata, many of the ornamental plants pictured on this site are not necessarily weedy and fun to cultivate. The idea is to educate and expand interest in Oxalis so that more people become students of the hobby and find out, like I did how enjoyable these little plants can be to grow.

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