Stevia

Family: Asteraceae (Aster family)
Genus: Stevia
Species: rebaudiana Bertoni

Looking to grow something fresh and fun to sweeten your prospects for the New Year? Stevia rebaudiana comes to mind. Just don’t call it a food plant and don’t try to sell it fresh, dried, or powdered for use as a sweetener. Stevia—sometimes called “candyleaf”—is considered by the U.S. Food and Drug Administration to be an unapproved food additive. It is approved (at this writing) by the FDA only as a dietary supplement. Why this is so is a long and complicated tale, one that won’t be told here. This column is about plants and not food. But the sweetener-or-supplement debate and attendant discussions about safety are just two of the factors that kept stevia under the radar and thus generally unavailable to home gardeners. Until recently few people in this country were even aware that stevia existed. As a consequence, and because its appearance is hardly eye-catching, it wasn’t given any shelf space along the houseplant aisle. There was little if any demand for seeds, much less starts. In fact, when I was first asked to feature this plant in 1999, it was very difficult to find any information at all about it—where to get seeds, how to get them to grow, how to care for the plant if they did.

Now that’s all changed. In 1999 I sent out an appeal for information about stevia. I’ve repeated my pleas through the years. At first, I heard nothing. Then, a few trickles of information found their way to my inbox. In the past year, it’s turned into a flood, including lists of commercial sources for both seeds and starts. I’ve heard most recently from the senior staff horticulturalist of a major purveyor of seeds and plants. Now I’m comfortable reporting that you’re likely to see stevia listed in at least one of your 2006 catalogs from both large- and small-scale seed companies. So to the Master Gardener who first asked me to find out about Stevia rebaudiana: Thanks for your patience!

Stevia is native to warm, dry places on our continent, ranging from what’s now the southwestern United States to Brazil and beyond. Stevia rebaudiana in particular is found most commonly in Paraguay, where it’s been used as a sweetener and herbal medicine by native peoples for centuries. Its unique properties were attractive to traders and botanists alike, and it was soon taken for study and cultivation to the university in Spain closest to Valencia. Today it’s a very popular sugar substitute in places as widespread as Brazil and Japan.

Stevia is 20 to 30 times sweeter than refined sugar, and this sweetness requires no processing or distillation. Drop a single fresh leaf into one cup of tea and you’ve added the equivalent of two lumps, not one. Two tablespoons of crushed, dried leaves can be as sweet as an entire cup of sugar. Because it’s now very popular, you’re likely to find powdered stevia on the shelves of most “natural” food stores and even some large “regular” groceries.

All this sweetness comes from the leaves of a rather homely little plant that at maturity can be up to 18 inches tall and as wide. It’s a perennial shrublet that won’t tolerate temperatures below 50° F. Grow it as a houseplant or treat it as an annual that’s set out only from June to September in our region. Bear in mind that temperatures can affect the sweetness, with heat having the edge. So the stevia you grow in Whatcom County will not be as sweet as stevia grown in Paraguay.

Stevia is easy to grow from seed, or you can use commercial starts or cuttings you’ve taken yourself. Your small plants will start slow, so give them time—along with good rich soil, full sun, warm air, and just enough water to keep the growing medium evenly moist. They’ll be quick to drown if you overwater and equally quick to die if you let the soil dry out completely. Remove the small white flowers that appear in summer and feed your plant with a water-soluble, high-nitrogen formulation—according to label instructions—to encourage leaf production. Your stevia will be vulnerable to aphids, mealy bugs, and spider mites, so keep an eye peeled and the insecticidal soap handy.

Use stevia leaves fresh or dry them for storage by settling them in single layers between paper towels set in a warm place for a week or so. Then use a spice grinder or mortar and pestle to reduce them to powder. It’s not much trouble and it won’t take much effort, so you won’t be burning many calories. Never fear. Use stevia in your tea and judge for yourself whether you’re able to pass up an equivalent amount of that full-bore sweetener we call “sugar.”

Photo: A picture of my stevia plant in St Louis. (July 2005) Source: Wikipedia