How to grow Sweet Potato in Australia
Sweet potato (Ipomoea batatas), also called kumara, is a sprawling, heat-loving vine grown from rooted shoots called slips. It needs four to five warm months to form its sweet tubers, so it is easy in Queensland and the tropics and possible in the south with a long, warm summer. The young leaves and shoots are edible too.
📖 Our full guide: How to Grow Sweet Potatoes in Australia: Slips and Planting
At a glance
When to sow by region
| Region | When to sow | Regional note |
|---|---|---|
| South East Queensland | September to February | |
| Northern Rivers NSW | September to February | |
| Sydney & Coastal NSW | October to December | A genuine Sydney win on the frost-free coast: plant slips Oct to Dec once soil passes 17°C, harvest 15 to 17 weeks later. West: plant after last frost. |
| Melbourne & Victoria | October to December | Plant slips from October to December once the soil reaches 20°C; earlier plantings have the best chance. The vines need 5 to 6 frost free months and the May frosts kill them, so this crop is risky but possible. |
| Adelaide & SA | October to December | Plant slips Oct to Dec once soil passes 18C. Harvest before winter; cold wet soil rots tubers. A long hot summer suits them. |
| Perth & WA | September to December | Plant slips Sep to Dec once soil passes 20C; later slips cannot bulk a tuber before the autumn cool. Source WA grown slips; quarantine blocks east coast plants. |
| Tasmania | Not suited | Unsuitable. Slips need five warm months and Tasmanian summers are too cool for tubers to bulk up. |
| Canberra & ACT | November and December | Very marginal. Plant slips Nov to Dec in the warmest bed; harvest before the April frost. Expect small yields. |
| North Queensland | September to February | Late dry/wet season. Sweet potato is tropical staple. Plant Sep to Feb; harvest dry season. Grows year-round. |
| Darwin & Top End | September to February | Late dry/wet season. Sweet potato is tropical staple. Plant Sep to Feb; harvest dry season. Grows year-round. |
Not to be confused with: Potato, which is a completely different plant in the tomato family. Sweet potato belongs to the morning glory family, and its leaves are edible while potato leaves are poisonous.
Where to plant
Sweet potatoes need full sun and loose, crumbly, well-drained soil improved with compost. Heavy clay gives misshapen tubers, so plant on raised mounds or ridges. Do not over-feed: rich soil and nitrogen give a huge mat of vine and few tubers.
The vines spread several metres and make a good living groundcover in a spare bed or around fruit trees. They need warm soil, about 17 to 20°C, at planting and four to five frost-free months to form tubers.
- South East Queensland, the Northern Rivers, North Queensland and Darwin: plant slips from September to February. In the tropics they grow all year.
- Sydney: plant from October to December once the soil is above about 17°C on the frost-free coast, and after the last frost in the west. Harvest about 15 to 17 weeks later.
- Adelaide: plant from October to December once the soil passes about 18°C, and harvest before cold, wet soil rots the tubers.
- Perth: plant from September to December once the soil passes about 20°C. Use slips from WA growers, as quarantine rules restrict bringing sweet potato in from the eastern states.
- Melbourne: possible but risky. Plant from October to December once the soil reaches about 20°C, in the warmest spot, and harvest before the May frosts.
- Canberra: very marginal; plant in November and December in the warmest bed and expect small yields. Hobart: not suited.
How to grow slips and plant them
- Buy certified slips from a supplier, or make your own: stand half a sweet potato in a jar of water or bury it in moist sand in a warm, sunny spot. In a few weeks it sprouts shoots.
- Snap off the shoots when they are about 15 to 20 cm long and stand them in shallow water until roots form.
- Make raised mounds or ridges of loose, composted soil.
- Plant the slips at an angle, burying about half their length, 40 to 60 cm apart.
- Water every day for the first week, then regularly while the vines establish.
Watering and feeding
Water regularly while the vines are establishing and spreading. Once they cover the ground and tubers are forming, water less: steady, moderate moisture gives the best tubers, while heavy watering late in the season can crack them, and soggy soil rots them.
Feed sparingly. Compost at planting is usually enough. A fertiliser low in nitrogen and higher in potassium suits them if the soil is poor.
Pruning and care through the year
- Where vines root into the soil along their length, lift them occasionally so energy goes into the main tubers rather than many small ones.
- Keep weeds down until the vines cover the ground; after that they smother most weeds.
- Pick young shoot tips and leaves as a green vegetable while the plants grow.
Harvesting
Sweet potatoes are usually ready about 16 to 18 weeks after planting in warm areas, longer in cool ones. Leaves often start yellowing when they are ready. Feel around the base of the plant for thickened roots and dig carefully with a hand fork from the edge of the bed, as the skin is easily damaged. Medium tubers, around 20 cm long, are the best eating; very large ones can turn woody.
In warm areas you can dig a few at a time as needed. In cooler areas, lift the whole crop before the soil gets cold and wet. Brush off the soil rather than washing, let them dry for a few days somewhere warm and airy, then store them wrapped in paper in a cool, dry, dark place, not the fridge. They keep for several months.
Growing in pots
Sweet potatoes can grow in a large pot or grow bag at least 40 cm wide and deep, filled with a light potting mix. Expect a smaller crop; let the vines trail over the edge and water regularly.
Using it
Roast, bake, mash or steam the tubers, or use them in curries, soups and salads. The young leaves and shoot tips are cooked like spinach and are good in stir-fries, curries and soups.
Keeping your own planting stock
Keep a few healthy, medium tubers from your harvest somewhere warm and dry over winter, then sprout them in late winter to make next season's slips. In frost-free areas, cuttings from the growing vines also root easily. Only use tubers free of weevil damage.
Varieties
- Beauregard (Orange)
- Murasaki (Purple Skin/White Flesh)
- Hawaiian Sunshine (Purple Flesh)
Companion planting
Sweet potatoes make a good living mulch in a summer bed or under taller crops.
Good companions
Pests and diseases
Sweet potato weevil is the most serious pest in warm areas. Rotation and clean planting stock are the best defence.
Pests to watch for
- Sweet potato weevil Small ant-like weevils on the vines, and tunnels with dark, bitter-smelling flesh inside the tubers. Rotate beds, use clean slips, harvest promptly and remove old vines.
- Nematodes Cracked, lumpy or knobbly tubers and poor growth in sandy soil.
Diseases to watch for
- Fusarium wilt Vines yellow and wilt, with brown streaks inside the stems.
- Scurf Brown or black blotches on the tuber skin. It is cosmetic only, but use clean planting stock.
Common questions
How do I grow sweet potato slips?
Stand half a sweet potato in a jar of water, or bury it in moist sand, somewhere warm and sunny. In a few weeks shoots grow. Snap them off at about 15 to 20 cm long and stand them in water until roots form, then plant them.
When should I plant sweet potatoes?
In spring and early summer once the soil is warm: September to February in Queensland and the tropics, October to December in Sydney, Adelaide and Melbourne, and September to December in Perth. Pick your region at the top of the page for the months.
How do I know when sweet potatoes are ready?
Usually about 16 to 18 weeks after planting, often when the leaves start to yellow. Feel around the base of the plant for thick roots and dig carefully from the edge of the bed.
Why do I have lots of vine but no sweet potatoes?
Too much nitrogen or rich soil gives leafy vines with few tubers. Feed sparingly, plant in loose soil, and give the plants enough warm months. Lifting vines that root along their length also helps.
Can you eat sweet potato leaves?
Yes. The young leaves and shoot tips are a good cooked green, used like spinach in stir-fries, curries and soups.
Can I grow sweet potatoes in Melbourne?
It is possible but risky. Plant slips from October to December once the soil is warm, in the warmest, sunniest spot, and harvest before the May frosts. Expect smaller yields than in Queensland.
How do I store sweet potatoes?
Brush off the soil rather than washing, dry them for a few days somewhere warm, then wrap them in paper and keep them in a cool, dry, dark cupboard. Do not refrigerate them. They keep for several months.
Sources we checked: Sustainable Gardening Australia: Sweet potato; Gardening Australia: Sweet potatoes.