Stevia

Stevia is usually raised as transplants, sown shallowly six to eight weeks before the last frost and germinated at 68–75°F over one to three weeks; seedlings are pricked out into cell flats and moved outdoors after frost danger has passed, spaced about 12 inches apart. Pinching back the growing tips during the first month or two encourages a bushier plant.

Growing on: The plant wants full sun to partial shade and an evenly moist, well-drained loamy or sandy soil; nitrogen-rich fertilizer should be avoided since it produces large leaves with little sweetness, while a balanced feed every four to six weeks and a mulch layer to hold moisture and cool the roots suit it better. It does not tolerate temperatures below 45°F, so in cooler climates it is grown as an annual or as a container plant brought indoors before frost, and it can also be propagated from stem cuttings taken from an established plant.

Stevia has no serious insect or disease problems, though aphids and spider mites are worth watching for. Overwatering can lead to root rot, and because its stems are delicate they break easily, so care is needed when weeding nearby.

Leaves are ready to pick roughly 90 days after planting, with the highest sweetness reached just as the plant begins to flower; pruning off the flower buds as they appear helps preserve that flavor. Harvesting in the morning, when sugar content is highest, and cutting the stems about six inches above the ground lets the plant regrow.

Storage: Cut stems are hung or spread to dry in a well-ventilated spot out of direct sunlight, then the dried leaves are kept in an airtight container in a cool, dry place; dried leaves are typically sweeter than fresh ones and can be ground into a powder.

Culinary: Stevia is grown for its intensely sweet, calorie-free leaves, which can be eaten fresh off the plant, steeped as tea, or dried and ground into a powder for sweetening beverages, baked goods, sauces, and salads.

Traditional: The Guaraní people of Paraguay, who called the plant caá-êhê or ka'a he'ê, used its leaves to sweeten teas and foods and chewed them as a sweet snack, a use recorded over centuries; leaves were also used traditionally in South America in preparations associated with diabetes, obesity, and hypertension.

Stevia rebaudiana is native to the warm, humid uplands of Paraguay and adjoining parts of Brazil, where the Guaraní people gathered and used the plant long before it drew outside notice. Swiss botanist Moisés Santiago Bertoni first described it scientifically in Paraguay in 1899, and it was formally named Stevia rebaudiana in 1905, honoring the Paraguayan chemist Ovidio Rebaudi, who had isolated its sweet compounds. Commercial cultivation later spread well beyond its native range, taking hold in Japan from the 1970s and extending today to Kenya, China, the United States, and other countries.