Stevia is the sweet-leaf plant: its leaves are intensely sweet, and a few dried and crumbled into tea or baking can replace sugar. In Zone 9 it is a tender perennial — it may survive a mild winter, but a hard freeze can finish it, so many gardeners grow it as a warm-season annual and replant each spring, or keep a pot to bring under cover.
Stevia is a slow starter but a generous plant once it is going. One or two plants, picked regularly through summer and autumn, will give you enough dried leaf for a household's tea for the year.
Zone 9 at a glance
USDA Zone 9 covers the warmest parts of the southern United States, including much of Florida, southern Texas, southern Louisiana, southern Arizona and coastal California. Winters are mild, with average winter lows of 20 to 30°F, and the growing season runs nearly all year.
The average last spring frost in Zone 9 is Jan 30–Feb 15, and the average first autumn frost is Dec 1–15. These are USDA zone averages drawn from NOAA frost records, not exact dates for any one garden — always check your local extension service and the forecast before planting tender crops outside.
| Detail | Zone 9 guidance |
|---|---|
| Average winter low | 20 to 30°F |
| Average last spring frost | Jan 30–Feb 15 (average/range) |
| Average first autumn frost | Dec 1–15 (average/range) |
| Days to germination | 7–14 days |
| Days to maturity | 90–120 days |
| Sowing | start indoors |
| Sun | full sun |
| Soil pH | 6.0–7.0 |
| Spacing | 18–24 inches |
| Water needs | moderate |
| Cold tolerance | tender |
When to plant stevia in Zone 9
Plant stevia in Zone 9 after the average last frost — from March through May, once nights are reliably warm — so plants have the whole hot season to grow. Plants mature in 90–120 days to a first harvest, and seed germinates in 7–14 days, though seed is slow and variable, so most gardeners start from nursery plants or cuttings. The average last spring frost is Jan 30–Feb 15 and the average first autumn frost is Dec 1–15 — USDA zone averages, not exact dates, so check your local extension service and the forecast before planting tender crops outside. Stevia is tender: the first frost will damage it, so the outdoor season runs roughly from March to December. Start seed indoors eight to ten weeks before the last frost for the earliest plants.
Work back from the frost dates rather than from a calendar date: the planting calendar hub gives the Zone 9 picture month by month. The month guides for March in Zone 9 and April in Zone 9 show what else is happening at planting time.
Starting stevia in Zone 9
Start stevia seed indoors in pots of seed-starting mix — sow on the surface or barely covered, since the seed needs light to germinate. Keep the soil warm and moist for the 7–14 days it can take to sprout, and give seedlings strong light. Germination can be patchy, so sow more seed than you need. Cuttings are more reliable: a stem cutting roots in water or moist compost in a few weeks. Harden plants off for a week to ten days before they go outside, and transplant only after the average last frost, when nights are reliably mild. Space plants 18–24 inches apart. Stevia grows into a bushy plant a couple of feet tall, so give it room.
Soil, spacing, sun and water
Stevia needs full sun and rich, well-drained soil with a pH of 6.0–7.0. Dig in well-rotted compost before planting — stevia is a hungry plant and pale leaves usually mean it needs feeding. Space plants 18–24 inches apart so air can move between them. Water needs are moderate: keep the soil evenly moist, especially in summer heat, and water at the base in the morning. Mulch helps keep the soil evenly moist. Stevia grows well in a large pot on a sunny patio, which also lets you move it under cover if a cold snap is forecast.
Companion planting
Good companions for stevia include tomatoes, peppers, marigolds and cabbage, and it fits well at the edge of a warm-season bed. Lemongrass is another tender warm-season plant that shares the sunny Zone 9 bed, and our guide to when to plant lemongrass in Zone 9 shows how its timing lines up with stevia. Rotate annual crops each year, and keep stevia where it gets full sun and good air movement. The companion planting finder can suggest combinations for your whole bed.
Pests and problems
The common pests to watch for with stevia are aphids, slugs and thrips. Aphids cluster on young tips — wash them off with a strong jet of water. Slugs nibble young plants, especially after rain; hand-pick them after dark and keep mulch pulled back from the stems. Thrips can distort leaves in hot weather; healthy, well-spaced plants cope better. In Zone 9, cold is a bigger threat than any pest — a frost will end the outdoor season, so keep a potted plant to bring indoors.
Harvest and storage
Harvest stevia 90–120 days after sowing, picking leaves as needed once plants are bushy — and take a main harvest just before the plant flowers, when the leaves are sweetest. Cut whole stems, hang them upside down in a shady, airy place to dry, then strip and store the leaves in a jar. Dried stevia leaf can be crumbled into tea or ground into a powder. Pick little and often through summer to keep plants bushy, and if frost is forecast, cut everything you can and dry it indoors rather than losing it to one cold night.
Frequently asked questions
When should I plant stevia in Zone 9?
Plant after the average last frost, from March through May. Seeds germinate in 7–14 days and plants mature in 90–120 days. It is tender, so the outdoor season runs roughly March to December.
Should I grow stevia from seed or cuttings?
Cuttings or nursery plants are more reliable — seed germination can be patchy and variable. Sow more seed than you need if you do start from seed.
When are stevia leaves sweetest?
Just before the plant flowers. Take a main harvest at that point, and pick regularly through summer to keep plants bushy.
Will stevia survive winter in Zone 9?
Sometimes — it may survive a mild winter, but a hard freeze can kill it. Grow it as a warm-season annual, or keep a potted plant to bring under cover.