Oxalis acetosella
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Oxalis acetosella, the wood-sorrel or common wood-sorrel, is a herbaceous rhizomatous flowering plant in the family Oxalidaceae. The specific epithet acetosella refers to its sour taste. The common name wood-sorrel is often used for other plants in the genus Oxalis.
In much of its range, most of Europe and parts of Asia, it is the only member of its genus and hence simply known as wood-sorrel.<ref name="BSBI">Template:Cite web</ref><ref name="Streeter">Template:Cite book</ref> While 'common wood-sorrel' may be used to differentiate it from most other species, this name is also used for the North American Oxalis montana.
Description
The plant grows up to Template:Convert tall.<ref name="tfb">Template:Cite book</ref> It has trifoliate compound leaves, the leaflets heart-shaped and folded through the middle, that occur in groups of three on the long petioles, and are finely pubescent. The flowers are produced singly on thin, wiry stems from spring to midsummer; they are small, open-faced, with five petals 8–15 mm long, which are white with pink or reddish venation.<ref name="Streeter"/> The flowers rarely appear reddish or mauve.<ref name="Clapham">Clapham, A.R., Tutin, T.G. and Warburg E.F. 1968. Excursion Flora of the British Isles. Cambridge University Press. Template:ISBN</ref>Template:Rp During the night or when it rains, the flowers close and the leaves fold.
Similar species
Anemonoides nemorosa (wood anemone) is similar. Both have white flowers, are small, and are found in woody shady places. Anemonoides nemorosa however has palmately lobed leaves and does not have true petals but large sepals which are petal-like.<ref name="Parnell">Parnell, J. and Curtis, T. 2012. Webb's An Irish Flora. Cork University Press. Template:ISBN</ref>
Distribution and habitat
It grows in woods and shady places across most of Europe and northern and central Asia.<ref name="POWO">Template:Cite web</ref> It is commonly found throughout Great Britain and Ireland, except for The Fens where it is rare.<ref name="BSBI"/><ref>Scannell, M.J.P. and Synnott, D.M. 1972 Census Catalogue of the Flora of Ireland Dublin Paperback. Stationery Office. ASIN: B0006CRR94 pp 127</ref> It occurs on a wide range of moist soils, both lime-rich and acidic, in Britain from sea level up to 1,160 m in central Scotland (and higher in southern Europe and Asia); it is also tolerant of deep shade, including even dense young conifer plantations.<ref name="BSBI"/> It formerly also occurred in Algeria in North Africa, but is now extinct there.<ref name="POWO"/>
Uses
As with other species of wood-sorrel, the leaves are sometimes eaten by humans, but are high in oxalic acid.<ref name="tfb" /> An oxalate called "sal acetosella" was formerly extracted from the plant by boiling it.
In culture
The common wood-sorrel is sometimes referred to as a shamrock and may be given as a gift on Saint Patrick's Day. This may have began in 1830, when an English botanist James Bicheno claimed wood sorrel to be true shamrock, due to its prettier trifoliate clover-like leaf, its early flowering in March, and because it can be eaten.<ref>Template:Cite book</ref> Despite this, it is more generally accepted that the plant described as "true" shamrock is a species of clover, usually lesser clover (Trifolium dubium).
Wood-sorrel is also known as Alleluia because it blossoms between Easter and Pentecost, when the Psalms which end with Hallelujah are sung.Template:Citation needed