How to grow sweet potatoes at home with little fuss

A crop that does most of the work while you get on with something else

Sweet potatoes are about as forgiving as a food crop gets, because they'll cope with ordinary soil, they shade out their own weeds once the vines take off, and they don't sulk the way a tomato does the moment conditions get less than perfect. What they do need is warmth and a long run at it, and that's the part worth understanding before you start, because getting the timing wrong is the only real way to fail at this one.

The timing, and the frost

Sweet potato is a warm season crop and it's frost tender, which matters around here because we do get frosts. The slips go out once the soil has genuinely warmed up and the risk of frost has passed, so spring into early summer, and they want somewhere between 4 and 5 months in the ground after that. Work backwards from your first frost and you'll see why putting them out early does you no favours at all.

Striking your own slips

You grow sweet potatoes from shoots, called slips, rather than from seed or from a piece of tuber the way you would with a spud. Take a firm tuber, sit it half submerged in a jar of water on a warm windowsill, and leave it alone. Over a couple of weeks it'll push out leafy shoots, and once those are 10cm to 15cm long you twist them off and stand them in water until they've grown roots of their own, at which point they're ready to plant.

It's worth knowing that supermarket tubers are often treated to stop them sprouting, so if nothing happens after a few weeks that's usually why rather than anything you've done.

Where to put them

Full sun and soil that drains freely is the whole requirement. Sandy or fairly ordinary ground suits them better than rich ground does, and a raised bed or a large pot works well if the yard is small, as long as you give the vines somewhere to run. Work some compost through beforehand so the soil is open rather than heavy, because a tuber swelling in compacted ground comes out small and knobbly.

Do not feed them the way you feed everything else

This is the one that catches people. A high nitrogen feed on sweet potatoes gives you a magnificent sprawl of leaves and almost nothing underneath, because the plant puts the growth where you've told it to. Go easy, use something gentle if you use anything at all, and let the poorer soil do its job.

Planting out and then leaving them to it

Put the rooted slips in about 30cm apart, water them in deeply, and mulch around them. From there it's an occasional deep water through dry stretches and not much else. The vines will sprawl a long way and that's them working, since the ground cover holds moisture in and keeps weeds down, so only trim them back if they're heading somewhere you need.

Lifting them

Around 4 or 5 months in, the leaves start yellowing off and that's your signal. Dig around the edge of the plant with a garden fork rather than a spade, because a spade will slice straight through a tuber you can't see, and lift the whole thing gently. Then leave them somewhere warm and shaded for a week to cure, which is what turns them properly sweet and lets them keep for months afterwards.

Keep a couple back

Set aside two of the best tubers and you never need to buy a starting tuber again, because next season's slips come off those. That's the bit that makes this crop worth the one season of figuring it out.

Shop related products

• Brunnings Garden Compost with Seaweed 25L. Work it through beforehand so the soil stays open.
• Martins Organic Sugar Cane Bale 11kg. Mulch around the slips once they go in.
• Brunnings Easy Wetta Potting Mix 70L. For anybody growing them in a big pot instead of a bed.
• Neutrog Seamungus Liquid 1L. A gentle feed, which is the only sort this crop wants.

Did you know we stock garden forks in the shop, which is what you want for lifting tubers without cutting them in half. Garden hand tools aren't listed on the website, so give us a ring on (08) 8536 4333 and we'll tell you what's in.

The garden centre carries the compost, the mulch and the feed for a bed like this, so have a look through the garden range or come in and we'll talk it over.

Read next

• How much sun does a vegetable garden actually need?
• How to keep a garden alive through a heatwave
• 7 habits that make a vegetable garden work

Anything that grows itself while I'm busy elsewhere is my sort of crop, and I make no apology for that.

Cheers,
Candeece