Submitted to the Contra Costa Times on February 1, 2006

Q. A friend gave me a plant called Stevia whose leaves are very sweet.  She uses them in lemonade and teas.  What is Stevia?

A. The herb, Stevia rebaudiana Bertoni is a perennial shrub of the aster family (Asteraceae). In its natural form Stevia is 10 – 15 times sweeter than sugar without the calories of sugar.  Extracts of its natural compounds are estimated to be 150 to 400 times sweeter than table sugar.   A native of Paraguay, it has been used for centuries by the indigenous natives as a traditional sweetener for their bitter teas.   It is widely used in many countries as the ideal replacement for sugar or synthetic sweeteners. Grown for its foliage, it also produces small white tubular flowers and blooms repeatedly.  Stems are long, flattened and twisted with small grey green rounded leaves. 

Stevia is difficult to grow from seed so it is best to start with plants obtained from a nursery or herbalist. Plants can sometimes be found in farmers markets.   The young plants are low temperature sensitive and you should wait until all danger of frost is past and soil temperatures are well into the 50s and 60s before you transplant them. They do best in loamy, mildly acidic well-drained soil in full sun, requiring at a minimum 3-4 hours of sunlight per day.  Since the feeder roots tend to be quite near the surface, care should be taken not to overwater them. However, don’t let them dry out completely.  During the summer months, frequent light watering is recommended.  Mulching around the plants will also keep the shallow roots from drying out.   The plants, which grow to about 30 inches tall and about 18 inches wide, should be planted about 18 inches apart.  Pinching off the flowers of the plant will make it become bushier with larger, sweeter leaves which some people harvest to use as a sugar substitute. Although it is considered a perennial, the best approach is to treat it as an annual herb like basil.  Fertilizer requirements are moderate.  Avoid high nitrogen chemical fertilizers.  Tilled into the soil before planting, slow release organic fertilizer or aged manure provides ideal nutrition since nitrogen is released slowly.  

Stevia also makes an ideal houseplant.  In the fall, you can cut back the garden plants hard, leaving a few leaves, and transplant into a pot that is at least 14” across with well-drained soil.  Grow them in a sunny window and maintain even soil moisture.  Or you can make your own cuttings from outdoor plants during the summer.  Three-inch tip cuttings dipped in rooting hormone will root in sand if misted frequently.  Some gardeners have had success by standing a cutting in a glass of water until the roots appear and then transplanting to a pot.

Attractive to bees, butterflies and birds, and resistant to most insects, Stevia is one of those ingenious herbs that makes herb gardening so rewarding.  .