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Scientific name: Oxalis violacea
Common name: 
Violet wood sorrel

(Information for this species page was compiled in part by Nicole Leninger for Biology 220M at Penn State New Kensington in Spring 2002)

Violet wood sorrel flowerViolet wood sorrel is a small, perennial wildflower found in open woodlands, moist prairies, thickets and waste areas from New England west to South Dakota, and south to Florida, Georgia, Louisiana, and Texas. Other names for this plant include “sheep sorrel,” “sour clover,” “trinity grass,” and “Indian lemonade.” These common names reflect a number of important morphological, physiological and ecological aspects of the plant: it can come to be quite abundant in sheep pastures (because sheep, like most herbivores, avoid eating it), it has a tri-parted leaflet (hence the “trinity”) that resembles the leaflets of clover, and it has sour tasting, acidic leaves (that can be used to brew a lemonade-like beverage). The scientific name of the genus (Oxalis) reflects the abundance of oxalic acid in the plant’s leaflets and stalks. Crystalline deposits of oxalic acid can even be found in the plant’s apical notch. The high concentrations of this sour tasting and mucous membrane irritating chemical explains the reluctance of most herbivores to consume this plant.

Habitat and Range
Violet wood sorrel grows best in sites with moderate to high levels of sunlight. Deeply shaded woods, then, are not ideal habitats for this species. The presence of violet wood sorrel is, in fact, a good indication that somewhere in a site’s history an open woodland or savanna-like habitat was once established.

In Massachusetts, violet wood sorrel is a “threatened” species and is found only in very limited sites and areas of the state. Its occurrence, though, in forty of the forty-eight contiguous states reflects its generally widespread distribution and robustness. Fire encourages flowering in colonies of violet wood sorrel. This positive response to fire probably is reflective of the species’ evolutionary history and association with prairie ecosystems.

Violet wood sorrel grows from rose-colored, subterranean bulbs. Its three-lobed, heart-shaped (“clover-like”) leaflets rise on short stalks to just above the soil surface. Taller (four to eight inches) flower stalks rise up over the leaflets. The flowers are small (half an inch or less wide), three petaled, and colored dark pink to purple.

Violet wood sorrel flowers in the spring and early summer. The petals open in the morning (between 8:00 and 9:30 am) but will remain tightly closed if the day is cloudy or rainy. Petals close in the late afternoon or early evening (between 4:00 and 6:00 pm). In one study it was determined that about half of the flowers of a violet wood sorrel patch live for only one day. The flowers are pollinated by a great variety of bees and other hymenopterans, lepidopterans and dipterans. Pollinators are attracted to the flowers by sweet secretions of the nectaries that are located at the bases of the staminal filaments.

Human Use
Human uses of violet wood sorrel have centered on the application of its acid-rich tissues and fluids to treat medical conditions.  Extracts of the plant tissues and solutions made by brewing and soaking the leaves and stalks in water have been used to treat mouth ulcerations, stomach disorders, and urinary tract problems. These preparations have also been used as appetite stimulators, diuretics, fever reducers, and as treatments for scurvy.

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