How to Grow Turmeric in Australia

Turmeric (Curcuma longa) is a leafy tropical perennial in the ginger family, Zingiberaceae, grown for its orange rhizomes (swollen underground stems) and white flower spikes. It thrives in warm, wet Queensland summers and grows as far south as Sydney, dying back each winter and shooting again in spring. The mistake most gardeners make is planting into cold soil, where the pieces rot before they sprout.

Three mistakes that matter

1. Planting into cold soil. A rhizome sitting in cold, damp soil does not shoot, and it often rots instead. Wait for the soil warmth given in When to plant, or start the pieces early in warm pots, as Pre-sprouting describes.
2. Letting the soil stay wet. Turmeric cannot stand waterlogging, least of all in winter, when the rhizome sits dormant (resting, with no leaves). Plant in free-draining soil or a raised bed, and stop watering once the tops die down.
3. Digging too soon. In warm zones rhizomes take 9 to 10 months to mature, so a clump lifted while its leaves are still green gives a small harvest. Wait for the signs described in Harvesting Rhizomes.

When to plant

Plant once the soil holds at least 20°C, the warmth turmeric needs to produce shoots, which in most gardens means spring. Plant once a year: an established clump shoots again by itself as the soil warms.

A late planting still grows, but the shorter season gives smaller rhizomes. At the cool edge of any window, start the pieces in pots on a seedling heat mat and plant out after the last frost.

Site, soil and setup

Rotate the bed, and grow a legume such as beans between turmeric crops. Where root-knot nematode is present, beans host it too, so leave the bed bare and weed free for a season instead. Black turmeric (Curcuma caesia) is a separate species from north-east India, not a colour form of turmeric, and it differs in the ways below. Ginger and galangal, its relatives, are separate crops and are not covered here.

Container growing

Pots suit every zone, and they are the surest way to grow turmeric where frost comes, because the plant can move under cover for winter. Use a pot of at least 40 L, about 40 cm across, filled with a quality potting mix. Both turmeric and black turmeric grow well in pots, and black turmeric, which likes more shade, suits a shaded patio.

• Watering: keep the mix evenly moist while the plant is in leaf, and check pots daily in hot weather, as watering pots in summer explains.
• Feeding: fish and seaweed blend at 25 mL per 9 L, fortnightly from the first shoots until the leaves yellow.
• Position: warm and sheltered, with morning sun and afternoon shade in hot districts.
• Winter: once the tops die down, keep the mix almost dry, and move the pot into a greenhouse or bright shed before frost.

Planting Rhizomes

Turmeric is grown from pieces of rhizome, not seed, planted in spring or started early in warm pots. Due to quarantine restrictions and our shipping policy, we cannot send turmeric or black turmeric rhizomes to the Northern Territory, Tasmania or Western Australia.

Pre-sprouting

• Choose firm, plump pieces about 6 to 8 cm long, each with at least two buds.
• Where a piece has been cut, let the cut end dry for a few days first, which reduces rot.
• Half-bury the pieces, buds up, in a shallow tray or small pots of damp potting mix.
• Keep them at about 21°C on the heat mat, and the mix barely moist.
• Plant out once shoots show and the soil holds the warmth When to plant gives.

Planting in the ground

Whether a piece arrives as a rhizome or a crown, plant it the same way.

• Set each piece 5 to 7 cm deep, with the buds facing up.
• Space turmeric 15 to 30 cm apart, in rows 30 to 45 cm apart, and black turmeric 30 to 45 cm apart.
• Water once, then keep the soil just moist, not wet, until shoots emerge.
• Shoots usually appear in 2 to 3 weeks in summer warmth, and often take longer in cooler spring soil.
• Put a label beside each planting, because nothing shows above ground for weeks.

Planting out sprouted pieces

• Harden off (accustom young plants to outdoor sun and wind) for about a week.
• In frost areas, wait until the last frost has passed.
• Plant with the rhizome 5 to 7 cm down and the shoots above the soil.
• Water in with seaweed solution at half strength, 15 mL per 9 L.

Care by growth stage

Warmth, steady moisture and a dry winter rest decide the harvest. Weeks count from planting and run shorter where autumn cold ends the season early, so go by the stage the plant shows.

Where winters are frost free, leave clumps in the ground; they shoot again in spring. Where frost comes, cut the dead tops to the ground, then lift the rhizomes or move pots under cover. Lifted pieces often dry out before spring, so in cold districts a potted clump kept almost dry under cover is the surer replanting stock.

Companion planting

Turmeric grows well beside low crops and light shade, and badly after crops that share its soil pests.

Grows well with

• Coriander, a short crop that fits along the edges of the bed.
• Onion, which sits low along the sides of a row without shading it.
• Corn, whose light shade suits turmeric in hot summers.

Keep apart

• Ginger in the same bed or the bed before, since it shares rhizome rot and root-knot nematode.
• Tomato and carrot in the bed before, where root-knot nematode is present, since both host it.

Harvesting Rhizomes

Harvest once the lower leaves turn yellow and the stems dry and fall over, about 9 to 10 months after planting in warm zones. Where autumn cold ends the season sooner, lift at die-back and expect smaller rhizomes.

• For a few pieces at a time, dig at the side of the clump and leave the rest growing.
• To take the whole clump, lift it with a fork, working well out from the stems.
• Dig 20 to 30 cm down to bring up the whole root ball.
• Rub off loose soil by hand, then break the clump into pieces.
• Cut off the stems with secateurs, 1 to 2 cm above the rhizome.
• Store the pieces kept for replanting in a cool, dry, frost-free place until spring.

Wrap fresh, unpeeled rhizomes loosely and keep them in the vegetable crisper, where they usually last a few weeks. For longer keeping, peel and freeze them, then grate them straight from frozen. Wear gloves, because the juice stains skin, clothes and cutting boards.

The leaves are useful too: wrap fish in them for cooking.

Common problems

Leaves yellow and collapse in autumn. This is usually the normal winter rest; harvest, or leave the clump as Care by growth stage describes. Soft rhizomes or galled roots point instead to the problems in Pests and diseases.

No shoots weeks after planting. Cool soil slows sprouting, so a firm piece is still alive while a soft one has rotted; see Three mistakes that matter.

Brown, scorched leaves. Hot afternoon sun or dry soil stresses the broad leaves; give the afternoon shade and extra water in heat that Care by growth stage describes.

Small rhizomes. Heavy shade, a short warm season or a crowded clump reduces the harvest; divide old clumps, as Tips describes.

No flowers. Flower spikes form on clumps left undisturbed for a year, so a clump lifted every season seldom flowers.

Potted plant does not return in spring. A dormant rhizome in cold, wet mix rots, so keep winter pots almost dry, as Container growing describes.

Pests and diseases

Turmeric is usually free of serious pests, and rot in wet soil is the bigger risk.

Rhizome rot (Pythium spp.). These water moulds are common in soil and thrive in wet conditions, rotting the rhizome, roots and stem base. Plants yellow in patches, and the stems pull away easily. Pull and bin affected plants, and plant only in free-draining soil.

Root-knot nematode (Meloidogyne spp.). These microscopic soil worms are very common in Queensland soils, and ginger is among their usual hosts. On turmeric they gall the roots and shrink the rhizomes, leaving plants stunted and unthrifty. Rotate beds, and dig in compost, which feeds the nematodes' natural enemies. Read more

Giant grasshopper (Valanga irregularis). This large native grasshopper, found from about Sydney north, chews the leaf edges and shoot tips of many herbaceous plants. Its nymphs feed from September to March, through turmeric's growing season. Pick them off by hand in the early morning, when they bask on top of the foliage. Read more

Prevention first

• Plant only firm, healthy pieces, with no soft or dark patches.
• Grow in free-draining soil or a raised bed, as Site, soil and setup describes.
• Rotate beds as Companion planting describes, and dig in compost before each planting.
• Water the soil rather than the leaves, and keep winter beds dry.

Tips

1. Leave one clump undisturbed for a year to see its white flower spikes. Cut them early in the morning and stand them in water straight away for the vase.
2. Divide each clump every 3 to 4 years and replant fresh pieces, so the bed does not crowd itself.
3. Pick leaves only sparingly while the plant grows, since it needs them to build the rhizomes.