Violet wood sorrel is a low, perennial herb with many flowers. Flowers in umbellike groups on long stalks, much higher than the leaves, 5-petaled, light magenta or lavender, rarely white (but never truly violet, despite the name), showy. Blooms April–July, also September–November. Leaves trifoliate (like clover), the leaflets heart-shaped, able to close along the central vein, often with purplish markings. Fruit a fairly long, upright capsule, surrounded by the calyx.
Similar species: Missouri has 4 native and 1 introduced Oxalis species. This is the only one that has magenta or lavender flowers, has leaves that arise only from the base of the plant, and grows from a bulb. The other species all have yellow flowers, leaves along the stem, and no bulbs.
Height: to about 6 inches.
Habitat and Conservation
Occurs in rocky or open woods, fields, prairies, and glades, and along rights-of-way, usually in acid soils.
The sour foliage adds a zesty flavor to salads, but this plant’s oxalic acid (named for the genus) limits the amount you should eat at any one time. Wood sorrel is thus both edible and toxic! Other plants famous for this chemical are spinach, sorrel, and rhubarb. Oxalic acid is the main active ingredient in the cleanser Bar Keepers Friend.
A South American plant in the same genus, O. triangularis, is often called "false shamrock." You can find it at florists and in garden centers, and is available with vibrant green or deep purple leaves. It is a well-known house and garden plant and is especially popular at St. Patrick's Day. Being a type of wood sorrel, it is unrelated to "true" shamrocks, which are believed to be some kind of clover (in the bean or pea family). It grows from corms and can sometimes be persistent as a weed in gardens.
Several insects visit the flowers for nectar or pollen, and a number of birds and mice eat the seeds. It is likely that herbivorous mammals, such as rabbits, eat the foliage, too, but they, like us, would be limited in the amount they can eat before getting sick.