How to Grow Sweet Potatoes
Sweet potatoes – Ipomoea batatas “Beauregard”
Written by Lars Lund
Edited by Louise Curley
Sweet potatoes with their sweet orange flesh make a tasty alternative to traditional potatoes. They’re native to warmer climates than that of the UK, which means, unless you live in a very mild part of the country, it’s best to grow sweet potatoes in borders in the greenhouse. The variety ‘Carolina Ruby’ is said to be the most reliable for crop production in this country.
While the tubers look potato-like, they are actually a root crop from the Ipomoea family and are related to the popular ornamental climber Ipomoea ‘Morning Glory’ – they share the same spreading habit and also have trumpet-like flowers. Unlike potatoes which are grown from tubers known as seed potatoes, sweet potatoes are grown from ‘slips’, which are long shoots that been removed from sprouted sweet potato tubers.
You can order slips from specialist mail order vegetable nurseries, which will be delivered in mid-spring. When they arrive they’ll probably look like they’ve wilted, so place them in a glass of water to revive them. The next step is to plant them up into 9cm pots filled with compost, burying the whole stem so that the compost comes right up to the leaves.
Sweet potatoes aren’t hardy so they’ll need to be protected from frost – the warm, humid conditions in a greenhouse are ideal to encourage them to start to form roots. You can then plant them out into the garden in a spot in full sunshine or into beds in the greenhouse.
If you plan to plant them outside, cover the area with black polythene in early spring to warm up the soil and to prevent weed growth. When you come to plant out the sweet potatoes cut slits in the polythene and plant into the holes.
Feed the plants every two weeks with liquid tomato fertiliser. They take 4–5 months to mature and the tubers can be lifted once the foliage has turned yellow. The tubers can be tricky to store so they’re best eaten soon after harvest.
Just like traditional potatoes they can be baked, fried, roasted or mashed.
Try this recipe for sweet potato fries.
For 4 people you will need:
- 6 sweet potatoes
- 1 teaspoon of olive oil
- Juice from a small lemon
- Ground pepper
- 1 ½ teaspoons of coriander
- 5cm of freshly grated ginger
- 2 small finely chopped red chillies
- ½ teaspoon of runny honey
- Chopped parsley
- Peel the potatoes and cut them in wedges or cubes.
- Mix the olive oil with the lemon juice, herbs, ginger and chilli, then mix in with the potatoes.
- Spread the potatoes on a baking tray and bake them in the middle of the oven at 200C for 20–25 minutes.
- Pour the honey on the potatoes and bake them for an extra 5 minutes.
- Season with salt and parsley.
Om Lars Lund
Danish horticulturist and journalist
Lars Lund has for many years engaged in the garden and greenhouse. Lars has published many books about greenhouses, and he has participated in many Danish horticultural TV shows. He is a walking garden encyclopaedia, and he has answers for most basic cultivation questions – also the more ambitious ones.