''Oxalis'' ( (British English) or (American English)) is a large

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

s in the wood-sorrel family,

Oxalidaceae The Oxalidaceae, or wood sorrel family, are a small family of five genera of herbaceous plants, shrubs and small trees, with the great majority of the 570 species in the genus ''Oxalis'' (wood sorrels). Members of this family typically have divid ...

, comprising over 550 species. The genus occurs throughout most of the world, except for the polar areas; species diversity is particularly rich in tropical

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

, and

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

. Many of the species are known as wood-sorrels (also as wood sorrels or woodsorrels) as they have an acidic taste reminiscent of the sorrel proper (''

Rumex acetosa Sorrel (''Rumex acetosa''), also called common sorrel or garden sorrel, is a perennial herbaceous plant in the family Polygonaceae. Other names for sorrel include spinach dock and narrow-leaved dock ("dock" being a common name for the genus ''Ru ...

''), which is not closely related. Some species are called yellow sorrels or pink sorrels after the colour of their flowers instead. Other species are colloquially known as false

shamrock A shamrock is a type of clover, used as a symbol of Ireland. The name ''shamrock'' comes from Irish (), which is the diminutive of the Irish word and simply means "young clover". At most times'', Shamrock'' refers to either the species ...

s, and some called sourgrasses. For the genus as a whole, the term oxalises is also used.

Description

The plants are annual or

perennial In horticulture, the term perennial ('' per-'' + '' -ennial'', "through the year") is used to differentiate a plant from shorter-lived annuals and biennials. It has thus been defined as a plant that lives more than 2 years. The term is also ...

. The leaves are divided into three to ten or more obovate and top-notched leaflets, arranged palmately with all the leaflets of roughly equal size. The majority of species have three leaflets, superficially similar to those of some

clover Clovers, also called trefoils, are plants of the genus ''Trifolium'' (), consisting of about 300 species of flowering plants in the legume family Fabaceae originating in Europe. The genus has a cosmopolitan distribution with the highest diversit ...

s. Some species exhibit rapid changes in leaf angle in response to temporarily high light intensity to decrease photoinhibition. The flowers have five petals, which are usually fused at the base, and ten

stamen The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...

s. The petal colour varies from white to pink, red or yellow;

anthocyanin Anthocyanins (), also called anthocyans, are solubility, water-soluble vacuole, vacuolar pigments that, depending on their pH, may appear red, purple, blue, or black. In 1835, the German pharmacist Ludwig Clamor Marquart named a chemical compou ...

s and

xanthophyll Xanthophylls (originally phylloxanthins) are yellow pigments that occur widely in nature and form one of two major divisions of the carotenoid group; the other division is formed by the carotenes. The name is from Greek: (), meaning "yellow", an ...

s may be present or absent but are generally not both present together in significant quantities, meaning that few wood-sorrels have bright orange flowers. The fruit is a small capsule containing several seeds. The roots are often tuberous and succulent, and several species also reproduce vegetatively by production of bulbils, which detach to produce new plants.

Ecology

Several ''Oxalis'' species dominate the plant life in local woodland ecosystems, be it Coast Range ecoregion of the

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

Pacific Northwest The Pacific Northwest (PNW; ) is a geographic region in Western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though no official boundary exists, the most common ...

, or the

Sydney Turpentine-Ironbark Forest Sydney is the capital city of the state of New South Wales and the most populous city in Australia. Located on Australia's east coast, the metropolis surrounds Sydney Harbour and extends about 80 km (50 mi) from the Pacific Ocean in ...

in southeastern Australia where least yellow sorrel ('' O. exilis'') is common. In the United Kingdom and neighboring Europe, common wood sorrel ('' O. acetosella'') is the typical woodland member of this genus, forming large swaths in the typical mixed deciduous forests dominated by downy birch ('' Betula pubescens'') and sessile oak (''

Quercus petraea ''Quercus petraea'', commonly known as the sessile oak, Welsh oak, Cornish oak, Irish oak or durmast oak, is a species of oak tree native to most of Europe and into Anatolia and Iran. The sessile oak is the national tree of Ireland, and an un ...

''), by sycamore maple (''

Acer pseudoplatanus ''Acer pseudoplatanus'', known as the sycamore in the British Isles and as the sycamore maple in the United States, is a species of maple native to Central Europe and Western Asia. It is a large deciduous, broad-leaved tree, tolerant of wind an ...

''), common bracken (''Pteridium aquilinum''), pedunculate oak ('' Q. robur'') and

blackberries BlackBerry is a discontinued brand of handheld devices and related mobile services, originally developed and maintained by the Canadian company Research In Motion (RIM, later known as BlackBerry Limited) until 2016. The first BlackBerry device ...

(''Rubus fruticosus'' agg.), or by common ash (''

Fraxinus excelsior ''Fraxinus excelsior'', known as the ash, or European ash or common ash to distinguish it from other types of ash, is a flowering plant species in the olive family Oleaceae. It is native throughout mainland Europe east to the Caucasus and Alb ...

''),

dog's mercury ''Mercurialis perennis'', commonly known as dog's mercury, is a poisonous woodland plant found in much of Europe as well as in Algeria, Iran, Turkey, and the Caucasus, but almost absent from Ireland, Orkney and Shetland.Sorbus aucuparia ''Sorbus aucuparia'', commonly called rowan (, also ) and mountain-ash, is a species of deciduous tree or shrub in the rose family. The tree has a slender trunk with smooth bark, a loose and roundish crown, and its leaves are pinnate in pairs o ...

''); it is also common in woods of common juniper (''

Juniperus communis ''Juniperus communis'', the common juniper, is a species of small tree or shrub in the cypress family Cupressaceae. An evergreen conifer, it has the largest geographical range of any woody plant, with a circumpolar distribution throughout the coo ...

'' ssp. ''communis''). Some species – notably Bermuda-buttercup (''O. pes-caprae'') and creeping woodsorrel (''O. corniculata'') – are pernicious, invasive weeds when escaping from cultivation outside their native ranges; the ability of most wood-sorrels to store reserve energy in their tubers makes them quite resistant to most weed control techniques. A 2019 study suggested that species from this

have a symbiotic relationship with nitrogen fixing ''Bacillus'' endophytes, storing them in plant tissues and seeds, which could explain its ability to spread rapidly even in poor soils. Tuberous woodsorrels provide food for certain small

herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...

s, such as the Montezuma quail (''Cyrtonyx montezumae''). The foliage is eaten by some

Lepidoptera Lepidoptera ( ) or lepidopterans is an order (biology), order of winged insects which includes butterflies and moths. About 180,000 species of the Lepidoptera have been described, representing 10% of the total described species of living organ ...

, such as the

Polyommatini Polyommatini is a tribe of lycaenid butterflies in the subfamily of Polyommatinae. These were extensively studied by Russian novelist and lepidopterist Vladimir Nabokov. Genera Genera in this tribe include: * '' Actizera'' * ''Acytolepis'' * ...

pale grass blue (''Pseudozizeeria maha''), which feeds on creeping wood sorrel and others, and dark grass blue (''Zizeeria lysimon''). ''Oxalis'' species are susceptible to the rust fungus ('' Puccinia oxalidis'').

Uses

As food

Several species of ''Oxalis'' are edible wild plants that have been consumed by humans around the world for millennia. In Dr. James Duke's ''Handbook of Edible Weeds'', he notes that the Native American

Kiowa Kiowa ( ) or Cáuigú () people are a Native Americans in the United States, Native American tribe and an Indigenous people of the Great Plains of the United States. They migrated southward from western Montana into the Rocky Mountains in Colora ...

people chewed wood sorrel to alleviate thirst on long trips, the

Potawatomi The Potawatomi (), also spelled Pottawatomi and Pottawatomie (among many variations), are a Native American tribe of the Great Plains, upper Mississippi River, and western Great Lakes region. They traditionally speak the Potawatomi language, ...

cooked it with sugar to make a dessert, the Algonquin considered it an

aphrodisiac An aphrodisiac is a substance that increases libido, sexual desire, sexual attraction, sexual pleasure, or sexual behavior. These substances range from a variety of plants, spices, and foods to synthetic chemicals. Natural aphrodisiacs, such as ...

, the Cherokee ate wood sorrel to alleviate mouth sores and a sore throat, and the

Iroquois The Iroquois ( ), also known as the Five Nations, and later as the Six Nations from 1722 onwards; alternatively referred to by the Endonym and exonym, endonym Haudenosaunee ( ; ) are an Iroquoian languages, Iroquoian-speaking Confederation#Ind ...

ate wood sorrel to help with cramps, fever and nausea. The fleshy, juicy edible

tuber Tubers are a type of enlarged structure that plants use as storage organs for nutrients, derived from stems or roots. Tubers help plants perennate (survive winter or dry months), provide energy and nutrients, and are a means of asexual reproduc ...

s of the oca (''O. tuberosa'') have long been cultivated for food in

Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...

and elsewhere in the northern

Andes mountains The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long and wide (widest between 18°S ...

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

. It is grown and sold in

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

as "New Zealand yam" (although not a true yam), and varieties are now available in yellow, orange, apricot, and pink, as well as the traditional red-orange. The leaves of scurvy-grass sorrel (''O. enneaphylla'') were eaten by

sailor A sailor, seaman, mariner, or seafarer is a person who works aboard a watercraft as part of its crew, and may work in any one of a number of different fields that are related to the operation and maintenance of a ship. While the term ''sailor'' ...

s travelling around

Patagonia Patagonia () is a geographical region that includes parts of Argentina and Chile at the southern end of South America. The region includes the southern section of the Andes mountain chain with lakes, fjords, temperate rainforests, and glaciers ...

as a source of

vitamin C Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits, berries and vegetables. It is also a generic prescription medication and in some countries is sold as a non-prescription di ...

to avoid

scurvy Scurvy is a deficiency disease (state of malnutrition) resulting from a lack of vitamin C (ascorbic acid). Early symptoms of deficiency include weakness, fatigue, and sore arms and legs. Without treatment, anemia, decreased red blood cells, gum d ...

. In

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

, creeping wood sorrel (''O. corniculata'') is eaten only seasonally, starting in December–January. The Bodos of north east India sometimes prepare a sour fish curry with its leaves. The leaves of common wood-sorrel ('' O. acetosella'') may be used to make a lemony-tasting tea when dried.

Other uses

In the past, it was a practice to extract crystals of

calcium oxalate Calcium oxalate (in archaic terminology, oxalate of lime) is a calcium salt of oxalic acid with the chemical formula or . It forms hydrates , where ''n'' varies from 1 to 3. Anhydrous and all hydrated forms are colorless or white. The monohydr ...

for use in treating diseases and as a

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

called ''sal acetosella'' or "sorrel salt" (also known as "salt of lemon"). Growing oca tuber

root cap The root cap is a type of tissue at the tip of a plant root. It is also called calyptra. Root caps contain statocytes which are involved in gravity perception in plants. If the cap is carefully removed the root will grow randomly. The root cap ...

s are covered in a

fluorescent Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with color ...

slush rich in harmaline and harmine which apparently suppresses pests. Creeping wood sorrel and perhaps other species are apparently hyperaccumulators of

copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...

. The

Ming Dynasty The Ming dynasty, officially the Great Ming, was an Dynasties of China, imperial dynasty of China that ruled from 1368 to 1644, following the collapse of the Mongol Empire, Mongol-led Yuan dynasty. The Ming was the last imperial dynasty of ...

text ''Precious Secrets of the Realm of the King of Xin'' from 1421 describes how ''O. corniculata'' can be used to locate copper deposits as well as for geobotanical prospecting. It thus ought to have some potential for

phytoremediation Phytoremediation technologies use living plants to clean up soil, air and water contaminated with hazardous contaminants. It is defined as "the use of green plants and the associated microorganisms, along with proper soil amendments and agronom ...

of contaminated soils.

As ornamental plants

Several species are grown as pot plants or as

ornamental plant Ornamental plants or ''garden plants'' are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Many flowering plants and garden varieties tend to be specially bred cultivars th ...

s in

garden A garden is a planned space, usually outdoors, set aside for the cultivation, display, and enjoyment of plants and other forms of nature. The single feature identifying even the wildest wild garden is ''control''. The garden can incorporate bot ...

s, for example, ''O. versicolor''. ''Oxalis'' flowers range in colour from whites to yellow, peaches, pink, or multi-coloured flowers. Some varieties have double flowers, for example the double form of ''O. compressus''. Some varieties are grown for their foliage, such as the dark purple-leaved ''O. triangularis''. Species with four regular leaflets, in particular '' O. tetraphylla'' (four-leaved pink-sorrel), are sometimes misleadingly sold as "four-leaf

", taking advantage of the mystical status of

four-leaf clover The four-leaf clover is a rare mutation of the common three-leaf clover that has four Leaflet (botany), leaflets instead of three. According to traditional sayings, such clovers bring good luck, a belief that dates back to at least the 17th cent ...

Selected species

* ''

Oxalis acetosella ''Oxalis acetosella'', the wood-sorrel or common wood-sorrel, is a herbaceous rhizome, rhizomatous flowering plant in the family Oxalidaceae. The Botanical name, specific epithet ''acetosella'' refers to its sour taste. The common name wood-sorr ...

'' – common wood-sorrel * '' Oxalis adenophylla'' – Chilean oxalis, silver shamrock * '' Oxalis albicans'' – hairy woodsorrel, white oxalis, radishroot woodsorrel, radishroot yellow-sorrel, California yellow-sorrel * '' Oxalis alpina'' – alpine sorrel * '' Oxalis ambigua'' * '' Oxalis articulata'' Savign. – pink-sorrel * '' Oxalis ausensis'' * '' Oxalis barrelieri'' – lavender sorrel * '' Oxalis bowiei'' – Bowie's wood-sorrel, Cape shamrock * '' Oxalis brasiliensis'' – Brazilian woodsorrel * '' Oxalis caerulea'' – blue woodsorrel * '' Oxalis caprina'' * '' Oxalis corniculata'' – creeping wood sorrel, procumbent yellow-sorrel, sleeping beauty, ''chichoda bhaji'' (India) * '' Oxalis debilis'' Kunth * '' Oxalis decaphylla'' – ten-leaved pink-sorrel, tenleaf wood sorrel * '' Oxalis dehradunensis'' * '' Oxalis depressa'' * '' Oxalis dichondrifolia'' – peonyleaf wood sorrel * '' Oxalis dillenii'' Jacquin – southern yellow woodsorrel, Dillen's woodsorrel, Sussex yellow-sorrel * '' Oxalis drummondii'' – Drummond's woodsorrel, chevron oxalis * '' Oxalis ecuadorensis'' * '' Oxalis enneaphylla'' – scurvy-grass sorrel * ''

Oxalis exilis ''Oxalis exilis'', the least yellow sorrel or shady woodsorrel, is a small herbaceous plant Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and n ...

'' – least yellow-sorrel * '' Oxalis frutescens'' – shrubby wood-sorrel * '' Oxalis gigantea'' * '' Oxalis glabra'' – finger-leaf * '' Oxalis grandis'' – great yellow-sorrel, large yellow woodsorrel * '' Oxalis griffithii'' Edgew. & Hook.f. * '' Oxalis hedysaroides'' – fire fern * '' Oxalis hirta'' – hairy sorrel * '' Oxalis illinoensis'' – Illinois wood-sorrel * '' Oxalis inaequalis'' * '' Oxalis incarnata'' L. – pale pink-sorrel * '' Oxalis lasiandra'' – Mexican shamrock * ''

Oxalis latifolia ''Oxalis latifolia'' is a species of flowering plant in the Oxalidaceae, woodsorrel family known by the common names garden pink-sorrel and broadleaf woodsorrel. It is native to Mexico and parts of Central and South America. However, it has propag ...

'' Kunth – garden pink-sorrel * '' Oxalis luederitzii'' * '' Oxalis luteola'' Jacq. * '' Oxalis magellanica'' G.Forst. * '' Oxalis magnifica'' Kunth – snowdrop wood-sorrel * '' Oxalis massoniana'' * '' Oxalis megalorrhiza'' – fleshy yellow-sorrel * '' Oxalis melanosticta'' * '' Oxalis micrantha'' – dwarf woodsorrel * ''

Oxalis montana ''Oxalis montana'' is a species of flowering plant in the family Oxalidaceae known by the common names mountain woodsorrel, wood shamrock, sours and white woodsorrel. It may also be called common woodsorrel, though this name also applies to its c ...

'' – mountain woodsorrel, white woodsorrel * '' Oxalis nelsonii'' – Nelson's sorrel * '' Oxalis norlindiana'' * '' Oxalis obliquifolia'' * '' Oxalis oregana'' – redwood sorrel, Oregon sorrel * '' Oxalis ortgiesii'' Regel – fishtail oxalis * '' Oxalis pennelliana'' * '' Oxalis pes-caprae'' – Bermuda-buttercup, African wood-sorrel, Bermuda sorrel, buttercup oxalis, Cape sorrel, English weed, soursob, " goat's-foot", " sourgrass", soursop (not to be confused with the fruit of that name) * '' Oxalis priceae'' – tufted yellow-sorrel * '' Oxalis pulchella'' * '' Oxalis purpurea'' L. – purple wood-sorrel * '' Oxalis rosea'' Feuillée ex Jacq. – annual pink-sorrel * '' Oxalis rubra'' A.St.-Hil. – red wood-sorrel * '' Oxalis rufescens'' * '' Oxalis rugeliana'' – coamo * '' Oxalis rusciformis'' * '' Oxalis schaeferi'' * '' Oxalis spiralis'' – spiral sorrel, volcanic sorrel, velvet oxalis * '' Oxalis stricta'' – common yellow woodsorrel, common yellow oxalis, upright yellow-sorrel, lemon clover, " pickle plant", " sourgrass, "yellow woodsorrel" * '' Oxalis suksdorfii'' – western yellow woodsorrel, western yellow oxalis * '' Oxalis tenuifolia'' – thinleaf sorrel * '' Oxalis tetraphylla'' – four-leaved pink-sorrel, four-leaf sorrel,

Iron Cross The Iron Cross (, , abbreviated EK) was a military decoration in the Kingdom of Prussia, the German Empire (1871–1918), and Nazi Germany (1933–1945). The design, a black cross pattée with a white or silver outline, was derived from the in ...

oxalis, " lucky clover" * '' Oxalis triangularis'' – threeleaf purple shamrock * '' Oxalis trilliifolia'' – great oxalis, threeleaf woodsorrel * '' Oxalis tuberosa'' – oca, oka, New Zealand yam * '' Oxalis valdiviensis'' – Chilean yellow-sorrel * '' Oxalis virginea'' – virgin wood-sorrel * '' Oxalis versicolor'' – candycane sorrel * '' Oxalis violacea'' – violet wood-sorrel * '' Oxalis vulcanicola'' – volcanic sorrel or velvet oxalis (MHNT) Oxalis articulata - Habit.jpg, '' Oxalis articulata'' Savign. subsp. ''rubra'' (A.St.-Hil.) Oxalis corymbosa 2.jpg, '' Oxalis debilis'' Kunth (syn. ''O. corymbosa'') Oxalis dehradunensis (Dun Ambushi) in Hyderabad, AP W IMG 9725.jpg, '' Oxalis dehradunensis'' Raizada, 1976 Oxalis gigantea 1.jpg, '' Oxalis gigantea'' Barneoud, 1846 Oxalis luteola 1.jpg, '' Oxalis luteola'' Oxalis magnifica 2.jpg, '' Oxalis magnifica'' R.Knuth, 1919 Oxalis priceae.jpg, '' Oxalis priceae''

Small Small means of insignificant size Size in general is the Magnitude (mathematics), magnitude or dimensions of a thing. More specifically, ''geometrical size'' (or ''spatial size'') can refer to three geometrical measures: length, area, or ...

Oxalis purpurea (Habitus) 2.jpg, '' Oxalis purpurea'' L., 1753