Photo by John Nelson This is a plant to dye for.

The process of dyeing, or otherwise coloring fabrics and textiles, has long been an important economic preoccupation, and many different, and unrelated plant (and animal!) species have been used around the world as sources of various dyes. Perhaps the most historically important was the indigo of commerce, derived from a plant named Indigofera tinctoria a very handsome plant bearing pink flowers and from which the rich, blue dye indigo was obtained.

This native of Asia (or perhaps Africa) figured heavily into the economy of colonial America. In the New World, indigo was first grown as a commercial crop in South Carolina in 1742, and the industry eventually spread to Georgia and North Carolina. Following that, indigo declined as an American industry and finally collapsed after the Civil War. Indigo dye, as a natural plant product, was later replaced by synthetic chemical sources, which were cheaper and much less labor-intensive to produce.

The mystery plant, though, is a member of a different genus, or group of species, all North American, some of which were in fact used as a substitute source for the true indigo. The genus name comes from a Greek word which means "to dye," which makes sense. A number of these American species are rather difficult to tell apart, and there remains considerable confusion as to the true identity of some of them.

Photo by John Nelson You can see this plant blooming in sunny places in the spring, often on sandy roadsides or open woodlands from Virginia south through the panhandle of Florida. It is a tough-stemmed herb, sometimes reaching 3' tall or more. Its stems are commonly greenish or even chalky grey. The smooth, slick leaves are divided into threes. The stalked flowers are always grouped in elongated racemes, usually stretching far above the leaves. Five milky white petals are present, the largest and upper-most petal often with a central splotch of purple.

The flower itself is a dead-ringer for a bean or pea blossom. Indeed, the curious roadside wonder is in the bean family and thus related to sweet-pea and kudzu and more distantly to mimosa and red-bud tyrees. After its petals fade and fall, a plump, stalked, thin-walled pod is formed, drying black and containing a considerable number of seeds. Plants are generally easy to sprout from seed and the are sometimes available from nurseries or growers. This perennial species is very easy to grow in the home garden, and once it gets established will come back regularly with a terrific spring show.

Answer to last week's mystery plant

Pomegranate, Punica granatum

Dr. John Nelson is 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