How to Grow Stevia

Growing guide

Overview

Stevia is a tender perennial herb grown for leaves that are naturally 200-300 times sweeter than sugar by weight. Gardeners grow it as a low-calorie sweetener source and as a productive container herb. It thrives in full sun, well-drained loamy or sandy soil, and consistent moderate moisture.

Soil & planting prep

Choose a loamy or sandy, well-drained site. Space transplants 12-18 inches apart and set them at the same depth they were growing in their pots. Stevia grows best in slightly acidic to neutral soil, around pH 6.0-7.0, but drainage is more important than perfect fertility.

When to plant

Start stevia seeds indoors 8 weeks before your average last spring frost date. Do not move plants outside until all frost danger has passed and nighttime lows stay reliably above about 50°F, since stevia is not frost-tolerant and is not a fall-planted crop. In USDA zones 8a-11b, plant in early spring after the last frost.

How to plant

1. Start seeds indoors 8 weeks before the last frost using a moist, well-draining seed-starting mix. Sow seeds on the surface and press them in lightly; do not cover them because stevia seeds need light to germinate.
2. Keep the tray around 68-75°F and the mix evenly moist but not soggy. Germination is often slow or spotty, so sow extra seeds or start from transplants if available.
3. Harden off seedlings for 7-10 days once outdoor temperatures stay above 50°F and all frost danger has passed.
4. Choose a full-sun location with loamy or sandy, well-drained soil. Space transplants 12-18 inches apart and plant them at the same depth as their container root ball.
5. Water transplants in thoroughly after planting and apply a light mulch to help retain soil moisture, keeping the mulch pulled back from the stems.

5 common mistakes to avoid

• Starting with old or buried stevia seed and then giving up after poor germination, because stevia seed is naturally slow and low-viability; buy transplants or sow fresh seed on the soil surface where it receives light.
• Putting plants outside before the last frost or while nights are still cool, because stevia is frost-tender and cold-stressed; wait until all frost danger has passed and nighttime lows stay above about 50°F.
• Letting flower buds develop and open before harvest, because leaf sweetness peaks before flowering and declines after; pinch buds or cut stems as soon as flower heads appear.
• Keeping the soil constantly wet or planting in heavy clay, because stevia roots rot in poorly drained soil; use loamy or sandy well-drained soil and water only when the top inch of soil feels dry.
• Leaving outdoor plants in the ground over winter in zones colder than 8a, because stevia will not survive hard frost; grow it in a 3-gallon pot and move it indoors before cold weather arrives.

Harvesting & storage

Begin harvesting once plants are bushy and well-established, typically 60-80 days after transplanting. Cut stems before flower buds open, when leaf sweetness is at its peak. Use leaves fresh, or dry stems in a warm, airy spot, then strip and crush the dried leaves and store them in an airtight container away from light.

Companion planting

Stevia grows well alongside basil, oregano, and other warm-season herbs that need full sun and well-drained soil. Keep it away from aggressive spreaders like mint, which can crowd it out.

Growing in containers

Stevia is well suited to containers. Use a 3-gallon pot with drainage holes and a well-drained potting mix; in zones colder than 8a, this makes it easy to move the plant indoors before fall frost to overwinter.

Pro tips

Start from transplants (seeds have low germination). Grow in a pot and overwinter indoors in frost-prone zones. Harvest leaves before the plant flowers — sweetness peaks pre-flower. Dry leaves and crush for sweetener.