How to grow sweet potatoes
There is so much to love about the sweet potato. Thought to have originally come from Central or South America, the sweet potato is now cultivated across the globe and features in cuisine from all corners of the world.
It’s a fantastically healthy vegetable rich in vitamins C and A, carotenoids, potassium and fibre, while being low in fat. It’s also hugely diverse with hundreds if not thousands of different varieties and ranges in colour from creamy yellow to orange and even purple. You can even eat the attractive leaves and shoot tips as a spinach substitute and they are related to the fast spreading but very pretty Morning Glory.
As a tasty alternative to potatoes, sweet potatoes are delicious and can be mashed, roasted, baked, sautéed or steamed, all of which means it’s a great choice for grow your own. If regular white potatoes are more your thing then you can read our guide to growing potatoes here.
Getting started with sweet potatoes
The first thing to bear in mind if you’ve decided to grow your own sweet potatoes, is to choose a variety that does well in the UK. They do not tolerate cold weather and ideally like temperatures of 24ºC, with lots of sunshine and warm nights too. It is best to purchase a variety that is suited to the British weather, these are Georgia Jet, Beauregard Improved, T65 and O’ Henry.
Growing your sweet potatoes from cuttings
It’s generally not a good idea to try and take cuttings from a shop or supermarket bought sweet potato, it is recommended to buy cuttings (or slips as they are also known) by way of mail order. When they arrive put the cuttings straight into water overnight and then pot them up the next day in individual containers, use either a multi-purpose or specialist seed and cutting compost. Make sure you cover the whole stem, right up to the leaves when potting up. Find more information on growing from cuttings here.
Alternatively you could try taking cuttings from a home grown sweet potato, which has been over wintered in a frost free place. To do this, you need to remove the shoots when they are between 5 and 7 cm long. Once you’ve potted your cuttings up, they need to be kept in a warm and humid room or in a propagator (read more on propagation first), these are the best ways to encourage growth and within 3-4 weeks, they should be ready to plant on.
Planting sweet potatoes outside
You’ll need to harden off your sweet potatoes before you plant them outside and prepare your soil well in advance. They like slightly acid soil so it may be worth checking your soil’s pH, you may find you need to mix in something like Sulphate of Iron. They’ll need well drained but moisture retaining soil, using mulch will help with this. Make sure you plant them about 30cm apart, as they are going to need plenty of room for their long stems and abundance of foliage.
Finally, if you are going to plant out, don’t do so until the risk of frost has passed (end of May, start of June) when the soil has warmed up. Consider planting them through a sheet of polythene, placed over the soil to keep them snug or growing them under a cloche or fleece tunnel.
Growing your sweet potatoes indoors
Containers or grow bags for potatoes are ideal for this in a greenhouse, but remember you may need to train the foliage on a trellis. Ideally feed them every 2 or 3 weeks with a general purpose fertiliser or a high potassium feed and pinch out the stems if they grow more than 60cm.
When to harvest sweet potatoes
In late summer to early autumn (3-4 months after planting), your sweet potatoes should be ready to harvest, but do make sure you harvest them before the frosty weather comes, otherwise they will start to rot in the ground. When you see the leaves start to turn yellow and die back, it’s time to lift them carefully taking care not to bruise them.
Our top 3 tips for growing sweet potatoes
- Although relatively pest free, sweet potatoes don’t like competition with weeds so keep their beds clear.
- Try not to water in the last 3 or 4 weeks of growth, this will avoid the tubers from splitting.
- You can store your sweet potatoes once you’ve lifted them, but you’ll need to ‘cure’ them first. Start by storing them in a warm place for 10-14 days, making sure that the potatoes aren’t touching each other. Once cured, wrap them individually in newspaper and store them, ideally at temperatures of 12ºC (not in a fridge) and they should last about 6 months.
Then all that is left to do is enjoy this super healthy vegetable.
Have you got any tips for growing sweet potatoes? If so we’d love to hear them, so please share them with us at @LoveTheGarden.