How to grow Stevia in Australia

Where to plant

Stevia needs full sun and a light, fertile, well-drained soil that stays moist. Its fine, shallow roots dislike both drying out and sitting in wet soil, so drainage matters. It does not survive frost, and in most areas it slows and dies back over winter.

Because it is frost tender, many gardeners grow it in a pot that can be moved under cover for winter.

• South East Queensland, the Northern Rivers, Sydney and Perth: plant from September to November. It may die back in winter and reshoot in spring.
• Melbourne and Adelaide: plant in October and November after frost. Mulch the crown over winter or keep it in a pot under cover.
• Canberra and Hobart: grow it as an annual or in a pot, planted in November or December after the last frost, and bring it under cover before autumn frost.
• North Queensland and Darwin: grow it through the dry season, planting from April to August (to July in Darwin), and harvest before the wet, when the stems tend to rot.

How to plant

1. Start with a nursery seedling or a cutting. Stevia seed germinates poorly, so plants and cuttings are far more reliable.
2. If sowing seed, surface sow on seed-raising mix, barely cover it and keep it warm and moist.
3. Plant in full sun about 30 cm apart, in soil improved with compost.
4. Water in and keep the soil lightly moist while it establishes.

Watering and feeding

Water moderately and steadily so the soil stays lightly moist but never soggy. Established plants tolerate short dry spells, but leaf production slows.

Feed lightly with a liquid fertiliser once the plant is growing. Go easy on nitrogen, which is reported to give leafy but less sweet growth.

Pruning and care through the year

• Pinch out the growing tips regularly to make the plant bushy.
• Remove flower buds as they form. Leaves are sweetest before flowering, and trimming the flowers improves leaf flavour.
• In autumn, cut the plant back and mulch the crown, or move a potted plant somewhere sheltered and frost free. It is semi-deciduous and usually reshoots in spring.
• Replace plants every few years, as they lose vigour.

Harvesting

Pick leaves once the plant is a good size, from about three months after planting. The sweetest leaves come late in the season, just before flowering. Before the first frost, cut the whole plant back and dry the leaves for winter.

To dry, hang stems in a warm, dark, airy place or spread the leaves on a tray, then crumble them and store them in a sealed jar. Fresh leaves keep about a week in the fridge.

Growing in pots

Stevia grows well in a pot at least 20 cm wide with a free-draining potting mix. Keep the mix lightly moist and move the pot under cover before frost.

Using it

Use a fresh leaf or two to sweeten tea, or steep fresh or dried leaves in hot water to make a sweet syrup. Dried, powdered leaves can sweeten drinks and stewed fruit. Use sparingly: the leaves are very sweet and have a slight liquorice aftertaste.

Propagation

Take tip cuttings through summer. Remove the lower leaves and set the cuttings in a free-draining potting mix, kept lightly moist and out of hot sun, until they root. Cuttings keep the sweetness of the parent plant, which varies between seedlings.