Sweet potato Growing Guide
Sweet potatoes are tropical climbing plants primarily grown for their edible tubers, which are harvested in early autumn. Their vigorous stems can reach 1.5m or more, and both the shoots and leaves can be consumed like spinach. They are tender plants requiring warmth and protection from frost.
This guidance applies to the crop in general. Individual varieties and local conditions can differ.
Planting information
Sweet potatoes are usually grown from cuttings (slips) or plug plants in spring, rather than from seeds. When cuttings or plug plants are received, plant them immediately into small pots of peat-free multi-purpose compost. Slips can also be rooted by standing them in a glass of water. Place pots in a propagator or cover with a clear plastic bag to maintain high humidity until plants are growing strongly. Keep in a warm, bright place with consistently moist compost. Move to slightly larger pots as they grow, watering with tepid water. To grow your own cuttings from tubers: In spring, place tubers in moist sand in a warm propagator or airing cupboard to encourage sprouting. Once leafy shoots are 5–7.5cm long, cut them off at the base and insert into small pots filled with peat-free multi-purpose or cuttings compost, then place in a propagator to root. In late spring or early summer, once young sweet potato plants have plenty of roots and are growing strongly, move them to their final growing site in a greenhouse, mini-greenhouse, or coldframe. Harden off plants first if planting outdoors. Plant in a large container (at least 30cm wide), grow bag, or in the ground. Set plants at the same depth they were previously growing, firm in gently, and water well. If planting in the ground, ideally inside a greenhouse or coldframe, choose a very warm, sheltered location in full sun with moisture-retentive, free-draining soil. Prepare soil by forking in well-rotted manure or garden compost (two bucketfuls per square metre). Plant young plants at least 30cm apart. If growing outdoors, cover the ground with cloches or plastic-free fleece for a few weeks before planting to warm the soil, and keep them covered after planting if possible.
Harvesting information
Harvest sweet potato tubers after four to five months, once the leaves turn yellow and die back, typically in early autumn before any frost. Gently tip the plant out of its container or lift it from the ground with a garden fork, taking care not to damage or bruise the delicate-skinned tubers. Any damaged tubers should be used immediately.
Storage information
Leave harvested tubers in warm sunshine for a few days to dry out their skin, which helps improve storage. However, they generally only keep for a few weeks, so it's best to harvest only one or two plants at a time as needed. Regularly check stored tubers for signs of deterioration or rot.