How to Grow Sweet Potatoes

Sweet potatoes, tropical climbing plants known for their edible tubers, thrive in warm conditions. Planted as cuttings in spring, they flourish in greenhouses or under cloches, delivering a bountiful harvest by early autumn.

These plants, scientifically named Ipomoea batatas, share similarities with morning glory and only a distant relation to traditional potatoes. Being tender perennials, they require frost protection and prefer temperatures between 21–26°C (70–80°F). For optimal growth, provide full sun, regular watering, and sheltered conditions. Greenhouse cultivation in large containers, growing bags, or borders ensures success, while outdoor planting demands warm climates and protective measures like cloches or fleece.

Sweet potatoes produce long, trailing stems reaching up to 1.5m (5ft), suitable for vertical trellises or sprawling ground coverage. Unlike regular potatoes grown from tubers, sweet potatoes start as cuttings, called slips, which need indoor warmth before transplanting outdoors in late May or early June, post-frost.

across the ground, depending on space availability.

Month-by-Month Guide

Harvesting and Storage

By early autumn, before the first frost, sweet potatoes are ready for harvest. For those looking to expand their vegetable garden, consider growing other root vegetables like regular potatoes. Visit our How to Grow Potatoes guide for tips on successful potato cultivation.

Choosing the Right Variety

Select a variety suited to your climate. UK gardeners should opt for hardy varieties like ‘Beauregard’ for outdoor success. Sweet potatoes come in various colors, including orange, purple, red, and white, each differing in sweetness and texture.

Buying and Propagating Slips

Sweet potato slips and plug plants (rooted cuttings) become available from online suppliers and garden centers from late April onwards. Alternatively, slips can be grown from store-bought tubers, though these may not be suited for colder climates.

To grow your own slips:

1. Place sweet potato tubers in moist vermiculite, perlite, or sand in a warm propagator or airing cupboard to encourage sprouting.
2. Once shoots reach 5–7.5cm (2–3in) long, cut them off at the base using a sharp knife.
3. Insert cuttings into small pots filled with multi-purpose compost and place in a warm propagator to root.

Planting Sweet Potatoes

Once the young plants develop strong roots, they can be moved to their final growing position in a greenhouse or outdoors under protective covers.

For greenhouse cultivation:

• Use large containers, growing bags, or borders filled with rich, well-draining soil.
• Provide trellises or supports to encourage vertical growth.

For outdoor planting:

• Choose a warm, sheltered spot with full sun and well-drained soil.
• Prepare the ground by incorporating compost or well-rotted manure and warming the soil with black polythene or cloches.
• Plant slips 30cm (1ft) apart through the polythene and cover with fleece or cloches for additional warmth.

Caring for Sweet Potatoes

• Watering: Keep the soil consistently moist but not waterlogged.
• Feeding: Apply a balanced liquid fertilizer every few weeks to encourage strong growth.
• Training Vines: Allow vines to climb supports or spread

By early autumn, before the first frost, sweet potatoes are ready for harvest. Gently lift tubers from the soil, taking care not to damage them. Cure freshly harvested tubers in a warm, humid environment for about 10 days to improve their flavor and longevity.

Properly cured sweet potatoes store well for months in a cool, dark, well-ventilated space. Additionally, the young shoots and leaves can be used as a nutritious green, similar to spinach.

By selecting the right variety and providing optimal growing conditions, sweet potatoes can yield a delicious, nutrient-rich crop, even in cooler climates.