Each week The Columbia Star features an explanation and picture of a mystery plant given by Dr. John Nelson, the curator of the USC Herbarium. To learn more about the Herbarium, call him at 777-8196. His department also offers free plant identification. www.herbarium.org

The week’s mystery plant, now in full bloom, might stir up memories of St. Patrick’s Day.

Its leaves are compound, each one bearing three deep–green, valentine–shaped leaflets, and, thus, it appears to be a sort of shamrock. The problem is that Saint Patrick’s shamrock may be a species of clover, in the bean family, which also has a similar leaf.

Answer to last week’s mystery plantShumard oak, Swamp red oak, Quercus shumardi It may be impossible to absolutely determine which plant represents the traditional shamrock of Irish legend. Once again, the problem stems from the use of common names, rather than scientific names. Clovers all belong to the genus Trifolium.

This plant is certainly not a species of Trifolium nor is it a member of the bean family at all. As similar as its leaves are to those of clover, its flowers are much different.

Borne in clusters atop softly downy stalks, these flamboyant, star– like blossoms bear five bright pink, sometimes white, petals, usually striped. Ten stamens will be present inside a flower, forming two whorls with five short and five long.

After the flowers fade, greenish capsules will develop, containing a number of tiny, reddish seeds. Some of its common relatives have yellow flowers. Another closely related species has speckled leaflets and grows in rich woods. All totaled, there are 800 species of its genus.

This plant grows throughout the Southeast. It is a native of South America but has escaped its garden confines, frequently showing up in lawns and along sidewalks forming patches or clumps.

Its weedy tendencies make it a nuisance to some. The scaly, bulbous roots must be dug up immediately in order to get rid of the plant. Once it really gets warm, the top parts of the plant will disappear.

This plant has a distinctly sour taste. In fact, an old name for this plant and its relatives is sorrel, which comes from an archaic word meaning sour. The taste is derived from a fairly high concentration of oxalic acid, which can be somewhat poisonous in large amounts.

Some species are eaten as a salad green and is rumored to make a fine sandwich slathered with mayo and between two pieces of white bread.