Stevia rebaudiana is a flowering herb native to the warm, semi-tropical regions of South America, specifically Paraguay and Brazil. For centuries, the Indigenous Guaraní people have used its leaves, which they call ka’a he’ẽ or “sweet herb,” to sweeten drinks and for medicinal purposes. Today, Stevia is known worldwide for the steviol glycosides within its leaves, primarily stevioside and rebaudioside A. These compounds provide a potent, calorie-free sweetness that can be 200 to 300 times stronger than table sugar, making it a popular choice for consumers and gardeners alike.
The Stevia Life Cycle: Perennial or Annual?
Stevia is botanically classified as a tender perennial sub-shrub, meaning it is naturally capable of living for more than two years. In its native habitat, which falls within USDA hardiness zones 9 through 11, the plant’s roots can survive the mild winter and send up new growth each spring. These warm, humid environments allow the plant to behave as a true perennial, forming a small, bushy shrub.
The plant’s perennial nature is severely limited by its extreme sensitivity to cold temperatures. Stevia cannot withstand frost, and its foliage will die back completely following the first hard freeze in temperate climates. Gardeners in regions colder than Zone 9, which includes most of North America and Europe, must therefore treat the plant as a frost-sensitive annual. Outside of tropical areas, Stevia is universally cultivated as an annual crop.
Optimal Growing Conditions and Climate Needs
To achieve its maximum potential for sweet leaf production, Stevia requires a consistently warm and sunny environment. The plant thrives best when placed in full sun, needing at least six hours of direct sunlight per day to encourage robust growth. However, in regions experiencing scorching summer heat, providing slight afternoon shade can help prevent the plant from wilting.
Stevia demands well-draining soil, as its roots are highly susceptible to rot if they become waterlogged. A light, fertile substrate, such as a sandy loam enriched with organic matter, provides the ideal structure. The soil should maintain a slightly acidic to neutral pH level, optimally falling within the range of 6.5 to 7.5.
Consistent watering is necessary to keep the soil evenly moist, particularly during the hot summer months. The plant’s growth is optimal in temperatures between 22 and 27 degrees Celsius; temperatures below 15 degrees Celsius significantly stunt its development. To ensure a long, productive growing season, avoid cold drafts and plant outdoors only after all danger of frost has passed.
Starting and Maintaining Stevia Plants
For the home gardener, starting Stevia from stem cuttings is generally the most reliable and efficient propagation method. Cuttings root quickly and reliably, typically establishing a root system within three to four weeks. This technique ensures that the new plants are genetically identical clones of the parent, preserving the desired sweetness profile.
Starting Stevia from seed is possible but often proves difficult due to low germination rates and the fact that many seeds are infertile. Regardless of the starting method, plants benefit from having their tips pinched back regularly. Pinching the tips encourages the plant to branch out, creating a bushier form that maximizes the yield of sweet leaves before the plant flowers.
For those gardening in cold climates, Stevia can be dug up before the first frost and potted to be overwintered indoors. The plant should be cut back to about six inches and kept in a sunny, cool location, treating it as a temporary houseplant until spring.