Stevia, known scientifically as Stevia rebaudiana, is a natural sweetener derived from a plant native to South America. Its leaves contain compounds, called steviol glycosides, that are significantly sweeter than sugar but have no calories. This makes stevia a popular choice for those seeking to reduce sugar intake. Understanding plant hardiness zones helps gardeners determine where and how this tender perennial can thrive.
Stevia’s Ideal Temperature Zones
Stevia is a tropical perennial, meaning it can live for multiple years in climates that do not experience freezing temperatures. It flourishes as a perennial in USDA Plant Hardiness Zones 8 through 11.
Stevia is not frost-hardy; temperatures consistently below 45°F (7°C) can cause significant stress or even kill the plant. While Zone 8 may require some protection, particularly during colder spells, Zones 9 and warmer generally provide ideal conditions for perennial stevia cultivation.
Cultivating Stevia in Cooler Regions
In regions colder than USDA Zone 8, stevia is cultivated as an annual. Seeds can be started indoors 6 to 8 weeks before the last expected frost, though germination is often slow. Many gardeners prefer purchasing young plants or propagating from cuttings for better success.
To extend the life of stevia in cooler climates, plants can be grown in containers and moved indoors before the first autumn frost. Before bringing plants inside, trim them back to about 6 inches in height. Indoors, stevia plants require a warm, sunny location, ideally with temperatures above 70°F (21°C). Supplemental light, such as from fluorescent grow lights, can prevent plants from becoming leggy.
When overwintering indoors, reduce watering to prevent root rot, as the plant’s growth slows. Stevia can also be overwintered by digging up the entire plant, trimming it back, and storing its roots in a cool, dark place, such as in sand or perlite. Come spring, once all danger of frost has passed and outdoor temperatures are consistently above 50°F (10°C), the plants or rooted cuttings can be transitioned back outdoors.
Essential Growing Conditions for Stevia
Stevia requires specific environmental conditions to thrive, regardless of its hardiness zone. Full sun exposure is preferred for stevia, promoting robust growth and leaf production. In extremely hot climates, however, some afternoon shade can prevent scorching. Stevia plants need at least 6 to 8 hours of direct sunlight daily for optimal health.
Stevia performs best in well-draining, loamy soil rich in organic matter. While its native soils are often acidic, stevia tolerates a wide pH range, ideally between 6.0 and 7.5. Consistent moisture is important, especially during its active growing season. The soil should remain evenly moist, but never waterlogged, as excessive wetness can lead to root rot. Raised beds or containers with good drainage holes are recommended for proper water management.