Sweet potato is a warm-season vine grown from rooted shoots called slips, planted once frost has passed and the soil is warm. In the tropics and warm subtropics it can go in for much of the year, while cooler regions have a shorter window. Expect roughly four months or more from planting to harvest.

It is one of the easier crops for a hot, sunny bed, provided you give the vines room and avoid wet, heavy soil.

How do you grow slips from a tuber?

Slips are the leafy shoots that grow from a tuber. The Brisbane City Council regrowing guide describes the simple method.

1. Stand a sweet potato in a jar of water with at least half of it submerged.
2. Leave it in a warm, bright spot for a few weeks until shoots form.
3. When the shoots are 10 to 15 cm long, twist them off the tuber.
4. Stand the slips in water until roots form, then plant them out.

Use a tuber from a healthy crop. Planting material is also one route by which pests such as weevil can arrive, so discard any tuber with tunnels, pitting or rot rather than propagating from it.

When should you plant, by climate zone?

Timing is driven by frost and soil warmth, not a fixed date. The Sustainable Gardening Australia sweet potato guide gives the following guidance, and Brisbane’s council gives a September to March season for the south-east.

Frost kills the foliage, so local frost patterns matter more than the calendar. Cool-climate crops take longer and may give smaller tubers. That is climate-dependent, so treat any one-season result as a guide only.

How much space do the vines need?

Sweet potato sprawls. Plan for it from the start.

• Plant slips into a low mound or raised bed. Brisbane City Council notes mounds improve drainage in subtropical conditions.
• Space slips 30 cm apart at the closest (Brisbane City Council) up to 40 to 60 cm (Sustainable Gardening Australia). Wider spacing suits a bed where vines will roam freely. Rows about 80 to 90 cm apart leave room to walk.
• In warm areas the vine can overwhelm neighbours, so give it its own bed or a large tub.
• If you grow other warm-season crops nearby, such as the ones in our guide to capsicum and chilli plants, keep a clear margin so runners do not smother them.

Training vines along a path edge or a low trellis is optional. If you cut vines back, leave plenty of healthy leaf so the plant can keep feeding the tubers.

How should you water and feed?

Water slips daily for the first week, then reduce as they establish. Keep the soil loose, moist and crumbly, with regular watering that stops short of waterlogging. Mulch helps hold moisture.

Prepare the soil with compost or well-rotted manure, but go easy on fertiliser. Sustainable Gardening Australia warns that heavy top-dressing encourages leafy growth over tubers. Rich, soft growth is a common reason for a lush vine with a poor crop, though other factors, such as short season or heavy soil, can also be involved.

When is it ready to harvest, and how do you cure it?

Brisbane City Council gives a harvest of usually four to six months after planting and notes crops can be ready in 16 to 18 weeks. Sustainable Gardening Australia gives a similar 16 to 18 weeks in warm climates and longer in cooler ones.

Signs it is time:

• Leaves yellow and begin to die back.
• A test dig shows tubers of a useful size. Sustainable Gardening Australia suggests tubers around 20 cm long, since very large ones can turn woody.

Dig carefully, starting well out from the plant, because the skin bruises easily. In pots, tip the container out and sift the soil.

Curing is a standard step before storage. The Washington State University Extension guide recommends about a week at roughly 27 to 32 degrees Celsius with high humidity and good ventilation, or two to three weeks if it is cooler. Avoid overheating and avoid moisture sitting on the skins, which causes mould. This is a US source, so use it for principles, and adjust to your own warm spot, such as a covered porch in a warm month.

After curing, store the tubers somewhere cool but not cold. WSU gives about 13 to 16 degrees Celsius, noting chilling injury below about 10 degrees and sprouting above about 16. A cool cupboard or unheated room works better than the fridge. Brush off dry soil rather than washing, and wrap tubers in paper. Sustainable Gardening Australia says they can keep for up to five months.

What are the common problems?

• Weevil damage. The sweetpotato weevil is a small, ant-like beetle about 5 to 7 mm long with a slender snout, a dark metallic blue or black head and rear, and a red middle and legs. The Pacific Pests and Pathogens fact sheet lists signs: small holes at the crown, tunnels and rot in stems, and shallow pits or tunnels in tubers. Tunnelled tubers can taste unpleasant. If you suspect it, check your state agriculture department for current advice.
• Hygiene that helps. Do not plant sweet potato in the same spot two years running. Hill soil over cracks in the bed, mulch to reduce cracking, harvest on time, and destroy leftover tubers and vine stems after harvest. The fact sheet calls clean-up of crop residues the most important step.
• Lush vines, few tubers. Heavy feeding is one documented cause (see above); drainage is another thing to check. Reduce feeding and check drainage.
• Rot. Waterlogged soil rots tubers. Use mounds and avoid overwatering.
• Leaf nibbling. Grasshoppers sometimes chew leaves. Sustainable Gardening Australia notes this is usually harmless.

Common mistakes to avoid

• Planting before the soil has warmed, or in the weeks before a frost.
• Digging too early, or leaving tubers in wet soil for months.
• Skipping the curing step, then storing tubers that rot or taste bland.
• Growing sweet potato in the same patch every year.

Keep simple records in your first season: planting date, first test dig and the weight of what you lift. Maturity times in the sources are ranges, so your own notes are the best guide for the next planting. Where the climate is marginal, a sunny, sheltered, free-draining mound is the single most useful thing you can offer.

If you also grow a warm-season rhizome crop, our guide to ginger in Australian gardens covers a different crop with similar needs for warmth and mulch. For sequencing across the season, the month-by-month subtropical planting calendar shows where sweet potato fits.