Stevia is the sweet-leaf herb — its leaves are many times sweeter than sugar, and the harvest is timed to catch that sweetness at its peak. The leaves are sweetest just before the plant flowers, in late summer, when the plant has had a full season of sun to build up its sweet compounds. Cut the whole plant at that moment, dry the leaves, and you will have a natural sweetener for the year. Pick too late, after flowering, and the leaves turn bitter.
Stevia takes 90–120 days to mature, according to the Garden Grove crop data. It is a tender herb in the Asteraceae family with moderate water needs. For the full growing picture, see our growing guide for stevia, and use the Harvest Date Calculator to work out your picking window from your sowing date. Browse the full guides hub and the tools hub for more harvest timing advice, and check your local extension service for dates suited to your climate.
Stevia at a glance
| Growing factor | What stevia needs |
|---|---|
| Days to maturity | 90–120 |
| Category | herb |
| Family | Asteraceae |
| Cold tolerance | tender |
| Water needs | moderate |
Signs stevia is ready to pick
Stevia leaves are ready for the main harvest in late summer, when the plant is about eighteen to twenty-four inches tall and bushy, with plenty of soft, bright-green leaves. The key sign is the flower buds: harvest when the buds are forming at the tips but have not yet opened, because that is when the leaves are at their sweetest. Taste a leaf — it should be intensely sweet with no bitter aftertaste.
Once the small white flowers open, the sweetness drops and a bitter note appears, so the harvest window is short — about a week or two. If the leaves are small, pale or yellowed, the plant may need more sun or water, or it may simply need more time. A healthy stevia plant in full sun with moderate water needs produces large, sweet leaves all summer.
How to pick stevia
Harvest stevia by cutting the whole plant, or the top two-thirds of it, with clean scissors or secateurs, cutting just above a leaf node so the plant can regrow. Take the stems in the morning after the dew has dried, when the leaves are dry and the sweet compounds are most concentrated. Handle the stems gently — the leaves bruise easily and bruised leaves dry badly.
Take the entire harvest at once for drying, rather than picking a few leaves at a time, because the main harvest is a drying harvest. If you only need a few fresh leaves for tea, snip the tips of a few stems and the plant will keep growing. For the full growing picture, see our growing guide for stevia.
The best time of day to harvest
Harvest stevia in the morning, after the dew has dried but before the sun gets hot. That is when the leaves are dry, crisp and most aromatic, because the essential oils are at their most concentrated after a cool night. Leaves picked in the afternoon heat are often limp and less flavourful, and wet leaves picked while the dew is still on them dry slowly and can go mouldy in storage.
Choose a dry day for harvesting if you can, and avoid picking after rain, when the foliage is wet and heavy. If you must pick on a damp day, spread the cuttings out in a single layer in a ventilated spot for an hour before you bundle or bag them. And get the harvest out of the sun straight away — a basket of cut herbs left in the sun for an hour will wilt and lose much of its aroma. Morning picking is a small habit that makes a real difference to flavour and keeping quality.
How often to pick
Stevia is a pick-little-and-often crop, and regular picking is part of good plant care, not just a way to get a harvest. Once the plant is established, you can take a small picking every week or two through the growing season, always leaving enough growth for the plant to recover. Each cut encourages the plant to branch and push out fresh, tender growth, so a plant that is picked regularly stays bushy and productive far longer than one that is left alone.
Do not wait for a single big harvest unless the plant is one you cut whole for drying — for most herbs, steady, small pickings give you better flavour and a healthier plant. Take a few sprigs from several plants rather than a large handful from one, and always leave at least two-thirds of the plant intact. If you go away for a few weeks, ask someone to pick the herbs, or cut the plant back before you leave so it regrows while you are gone.
What happens if stevia is left too long
Stevia left unpicked past flowering loses its sweetness and gains a bitter, liquorice-like aftertaste that makes the leaves unpleasant to use. The plant puts its energy into seed, the leaves become small and coarse, and the overall quality drops sharply. An unharvested plant in a cold climate will simply die with the first frost, and the whole season's sweetness will be lost.
If your stevia has flowered, harvest it anyway and taste the dried leaves — they may still be usable in small amounts, mixed with a little sugar or honey to balance the bitterness. Better still, cut the plant back hard after flowering and it will often push out a flush of fresh, sweet leaves before the frost. The lesson is to watch the flower buds closely in late summer, because the sweetest window lasts only a week or two.
How to store stevia
Drying is the point of the stevia harvest. Strip the leaves off the stems and spread them in a single layer on a tray in a warm, dark, well-ventilated spot for one to two weeks, until they are crisp and crumble easily. Alternatively, hang small bunches upside down. Use the Herb Drying Calculator for timing. Do not dry stevia in sunlight, which weakens the sweetness.
When fully dry, crush the leaves into a fine powder with a mortar or a spice grinder, and store the powder in a sealed jar in a dark cupboard. Dried stevia powder keeps for a year or more. Use it sparingly — a pinch sweetens a cup of tea, and too much tastes bitter. Fresh stevia leaves keep for about a week in the fridge in a bag, but the dried powder is far more useful.
Succession and continuous harvest tips
Stevia is a tender perennial with moderate water needs, grown as an annual in cold climates and harvested before the first frost. In warm climates it can live for several years, but it is usually treated as an annual because the first-year leaves are the sweetest. Sow or plant new stevia each spring, after the last frost, in full sun and well-drained soil.
The harvest rhythm is simple: pick a few fresh leaves through summer, then take the main harvest in late summer just before flowering, and cut the plant back to encourage a second flush if the weather stays warm. In cold climates, take a final harvest before the first frost and check your local extension service for your frost dates. Bring a potted plant indoors for winter if you want fresh leaves year-round.
If you are also growing other herbs and vegetables, our guides to harvesting catnip and harvesting basil follow the same picking principles, and check your local extension service for advice suited to your area.
Frequently asked questions
When is stevia ready to harvest?
In late summer, when the plant is bushy and flower buds are forming but not yet open, typically 90–120 days after planting. That is when leaves are sweetest.
How do I harvest stevia?
Cut the top two-thirds of the plant just above a leaf node, in the morning after the dew has dried, and dry the leaves for powder.
Should I dry or use stevia fresh?
Dry it — dried stevia leaves crushed to powder keep for a year or more and are far more useful than fresh leaves.
Why do my stevia leaves taste bitter?
They were probably picked after flowering, when sweetness drops and bitterness appears. Harvest just before the flowers open.
Can stevia survive winter?
Only in warm climates. It is tender, so in cold areas grow it as an annual and take a final harvest before the first frost.