Photo by John Nelson 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 Nelson at 777-8196. His department also offers free plant identification. www.herbarium.org

Whatever humor this little plant might have must be truly tasteless. Well, its fruits are tasteless, anyway.

The fruits are gorgeous, brilliant red, and dead ringers for the cultivated strawberry. Although when bitten, there is only a watery flavor, and not much else. Sort of like damp cardboard.

Answer to last week’s mystery plantWindowbox wood-sorrel, Red wood–sorrel, Oxalis rubra The true strawberries belong to a plant genus called Fragaria, which has several species in Europe and North America. In fact, there are a couple of native wild strawberries in the eastern US.

All of the true strawberries are characterized by flowers with five sepals and five petals, many slender stamens, and a large number of tiny, separate pistils. They are set apart by white petals, and a fruit which is juicy and very sweet.

This week’s mystery plant, although not a true strawberry, has very similar flowers, but the petals are bright yellow. Its fruit is somewhat dry and mealy, and has practically no taste at all.

This curious plant, being closely related to the true strawberries, shares an important fruit characteristic with them. They all produce what botanists call an aggregate fruit.

In this case, the interior of the flower (the receptacle) swells dramatically after pollination. Each pistil on the surface of the receptacle develops a single tiny, dark, enclosed seed, or achene.

Many dozens of these tiny achenes will dot the exterior of a mature strawberry. Technically , a single flower produces several dozen tiny, dry fruits, all studding the exterior of the swollen receptacle.

This species is common through all of the eastern US and occurs on the Pacific Coast as well. It mostly skips the interior between Texas and Arizona.

It is not a native species, but comes from Asia and is known from Japan through India and the Himalayas. In fact, it has become a fairly common introduction in many parts of the globe including Europe, Africa, and the New World.

Now naturalized, it is commonly seen in gardens as something of a weed. It seems to prefer moist soil, and it can endure considerable shade. Many people tolerate it in their gardens as a benign little pest as the flowers and fruits are attractive and birds probably eat the fruits.