Native to Paraguay, Colombia, Venezuela, and Brazil. For growers of this herb, life is sweet indeed: Extracts from the leaves contain a noncaloric compound called stevioside, a substance that is 100 to 300 times sweeter than sugar. Because stevia does not cause tooth decay and has a negligible effect on blood sugar, it has become a popular sweetener.
Stevia is a shrubby plant to 112 ft. tall and about 1 ft. wide, with toothed, oblong to lance-shaped, papery-textured leaves to about 2 in. long. Clusters of small white flowers with purple throats appear in summer atop wandlike stems.
Start with plants purchased at a garden center or from a mail-order nursery. Choose a site with full sun and moist, fertile, well-drained soil. Stevia does equally well in the ground or in pots, but it will not tolerate frost. Propagate by cuttings taken in summer. Wait until late fall to harvest leaves, as cool temperatures and short days intensify the sweetness. Cut stems near the base of the plant and place them on a net or screen to dry. When stems and leaves have dried completely, strip and crush the leaves. Foliage retains its bright green color even when dry.