Sweet Potatoes in Your Garden: How to Grow Sweet Potatoes

Growing sweet potatoes successfully in Britain requires embracing a few fundamental differences from traditional potato cultivation. You’ll be starting with slips (rooted shoots) rather than seed potatoes, providing consistent warmth throughout the growing season, and working with a much longer timeline. But when you harvest those gorgeous orange tubers in autumn, you’ll understand why more British gardeners are giving them a go. I’ve found that with the right preparation and realistic expectations, even gardeners in cooler regions like Yorkshire can produce a respectable crop.

How to Grow Sweet Potatoes

Before you start growing sweet potatoes, gathering the right materials will make your job considerably easier. I’ve learned through trial and error that cutting corners on certain items leads to disappointing yields, whilst other supplies can be quite basic.

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Essential Equipment and Materials

You’ll need sweet potato slips, which are the young shoots grown from a mature sweet potato. You can buy these from specialist suppliers or propagate your own from shop-bought sweet potatoes, though I’d recommend purchased slips for your first attempt. A sunny, sheltered growing spot is absolutely critical, whether that’s a south-facing greenhouse bed, large containers, or a warm patch of open ground with cloches available.

For soil preparation, you’ll want well-draining compost mixed with horticultural grit or sharp sand. Sweet potatoes detest waterlogged conditions. I use large containers (at least 40 litres) filled with multipurpose compost when growing in my greenhouse, which gives excellent control over soil conditions. If you’re planting directly in the ground, you’ll need black plastic mulch or landscape fabric to help warm the soil and suppress weeds.

Optional But Helpful Items

A propagation mat or heated propagator makes slip production much more reliable in our climate. Garden fleece or cloches are brilliant for protecting young plants during cool spells, and I keep mine handy throughout the season. A soil thermometer helps you judge when conditions are right for planting, as sweet potatoes need soil temperatures above 15°C to grow actively.

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Liquid seaweed feed or a balanced organic fertiliser supports healthy growth without encouraging too much leafy vegetation at the expense of tubers. I’ve also found that having support structures like bamboo canes can help if you’re growing vigorous varieties that produce long, trailing vines.

Step-by-Step Instructions

Step 1: Starting Your Slips

If you’re producing your own slips, start this process in late February or early March. Select a healthy, firm sweet potato without any soft spots or damage. Suspend it in a jar of water using cocktail sticks, with about half the tuber submerged. Place this in a warm, bright location like a south-facing windowsill.

Within a few weeks, shoots will emerge from the sweet potato. Once these slips reach about 15cm long, gently twist them off from the parent tuber. Place each slip in a glass of water until roots develop, which typically takes one to two weeks. I’ve found that changing the water every few days prevents bacterial growth and keeps the slips healthy.

Alternatively, you can purchase ready-to-plant slips from specialist suppliers, which arrive in late spring. This option is more reliable for beginners and ensures you’re getting varieties suited to British conditions. Popular choices include ‘Beauregard’ and ‘Georgia Jet’, which mature relatively quickly.

Step 2: Preparing Your Growing Area

Sweet potatoes need the warmest spot you can provide. In my experience, a greenhouse or polytunnel gives the best results in most of Britain, though southern gardeners with very sheltered, sun-baked spots can succeed outdoors. The soil must be light and well-draining, as heavy clay will lead to rotting and poor tuber formation.

For container growing, fill large pots with a mixture of three parts multipurpose compost to one part horticultural grit. This ensures excellent drainage whilst providing adequate nutrients. If planting in greenhouse beds or outdoor plots, dig in plenty of compost and sharp sand to improve soil structure. Avoid adding too much nitrogen-rich fertiliser, as this encourages leaf growth over tuber development.

When growing outdoors, cover the planting area with black plastic sheeting about two weeks before planting. This warms the soil significantly and gives your sweet potatoes a better start. Cut planting holes in the plastic when you’re ready to plant.

Step 3: Planting Out

Wait until late May or early June before planting out, when all risk of frost has passed and nighttime temperatures reliably stay above 10°C. I’ve planted too early before and watched my slips sulk and refuse to grow, so patience truly matters here.

Plant slips about 30cm apart if growing in the ground, or one to three slips per large container depending on size. Make a hole deep enough to bury the slip up to its lowest leaves, then firm the soil gently around it. Water thoroughly after planting, then keep watering regular until the plants establish.

If there’s any chance of cool weather in the first few weeks after planting, cover the plants with fleece overnight. Sweet potatoes are tropical plants at heart and really struggle with temperatures below 10°C. I keep fleece handy throughout June just in case.

Step 4: Caring for Growing Plants

Once established, sweet potatoes produce vigorous, trailing vines that can cover quite a large area. In a greenhouse, I train these along the ground or up support structures. Outdoors, the vines will sprawl across the black plastic mulch, which helps keep the soil warm.

Water regularly but don’t overdo it. Sweet potatoes are quite drought-tolerant once established and actually prefer slightly drier conditions. I water deeply once or twice weekly during dry spells, less frequently in cooler weather. Overwatering leads to excessive leaf growth and small tubers.

Feed fortnightly with a liquid fertiliser high in potassium (like tomato feed) from mid-July onwards. This encourages tuber formation rather than just leafy growth. Some gardeners pinch out the growing tips to encourage bushier plants, though I’ve found this makes little difference to final yields in our climate.

Step 5: Harvesting Your Crop

Sweet potatoes need a long growing season, typically 100 to 150 days from planting. In Britain, this means harvesting in September or October, before the first frosts arrive. The plants will tell you they’re ready when the leaves start to yellow, though you can harvest earlier if frost threatens.

Dig carefully around the base of each plant, working outwards to avoid damaging the tubers. Sweet potato skins are quite delicate when freshly dug, so handle them gently. I use my hands to feel around in the soil rather than relying solely on a fork, which can easily pierce tubers.

Don’t expect massive yields like you’d achieve in warmer climates. In my Berkshire plot, I typically harvest two to four decent-sized tubers per plant, with several smaller ones. This might seem modest, but the flavour of homegrown sweet potatoes is considerably better than shop-bought options.

Step 6: Curing and Storing

This step is crucial but often overlooked. Brush off excess soil but don’t wash your sweet potatoes immediately after harvest. Place them in a warm location (around 25-30°C) with high humidity for 10 to 14 days. This curing process heals minor damage, converts starches to sugars, and dramatically improves storage life.

I cure mine in a heated greenhouse or even near a radiator indoors, placing them in cardboard boxes lined with newspaper. After curing, store sweet potatoes in a cool but not cold location, around 12-15°C. A pantry or utility room works well. They’ll keep for several months under these conditions, though I find ours rarely last that long before being eaten.

Common Mistakes to Avoid

Planting Too Early

The single biggest mistake I see gardeners make is rushing to plant sweet potatoes in April or early May. These plants absolutely need warm conditions to thrive, and exposing them to cold soil and chilly nights severely stunts their growth. You won’t gain any advantage by planting early, in fact, you’ll likely end up with smaller plants that produce less.

Wait until late May at the earliest, and early June is safer in northern regions. The soil should feel warm to the touch when you place your hand on it. If you’re shivering whilst planting, it’s too cold for sweet potatoes. I’ve seen plants planted in proper warmth overtake those planted three weeks earlier in cool conditions.

Growing in Heavy, Poorly-Drained Soil

Sweet potatoes form tubers underground, and if those tubers are sitting in cold, waterlogged soil, they’ll rot rather than grow. Clay soils are particularly problematic unless heavily amended. I learned this lesson the hard way during a wet summer when half my outdoor crop rotted in heavy ground.

If your soil is heavy, either grow in raised beds with imported compost, use large containers, or dig in enormous amounts of sharp sand and organic matter. The soil should drain freely whilst still retaining some moisture. When you squeeze a handful, it should clump together but easily break apart.

Overwatering Established Plants

Whilst young slips need regular watering to establish, mature sweet potato plants prefer drier conditions. Overwatering leads to excessive vine growth, small tubers, and increased disease risk. I water established plants only during prolonged dry spells, and even then quite sparingly.

The leaves may wilt slightly on hot afternoons, but this is normal and they’ll recover in the evening. Only water if plants remain wilted in the morning or if the soil is completely dry several centimetres down.

Using Nitrogen-Heavy Fertilisers

Sweet potatoes don’t need particularly rich soil, and high nitrogen levels cause them to produce masses of leaves whilst forming small, disappointing tubers. I made this mistake in my first year, treating them like courgettes and feeding weekly with a general-purpose fertiliser.

Use a balanced fertiliser sparingly at planting time, then switch to a high-potassium feed (like tomato fertiliser) once the plants are well established. This promotes tuber formation rather than excessive foliage.

Not Protecting from Early Frosts

Sweet potato plants are extremely frost-sensitive, and even a light frost will kill the foliage and halt tuber development. In Britain, we often get early autumn frosts that can catch you unawares. Keep an eye on weather forecasts from mid-September onwards, and be prepared to harvest early if necessary.

I cover my outdoor plants with fleece if frost threatens before I’m ready to harvest. This can buy you an extra week or two of growing time, which makes a real difference to final tuber size.

Expert Tips

Choose the Right Varieties

Not all sweet potato varieties suit British conditions. Look for early-maturing types that can produce a crop within our shorter growing season. ‘Beauregard’ is reliable and widely available, whilst ‘Georgia Jet’ matures even faster. ‘Erato’ produces attractive purple-skinned tubers and handles cooler conditions reasonably well.

I’ve experimented with various varieties, and those marketed specifically for cooler climates consistently outperform standard commercial types. Whilst the latter might work in an exceptionally warm summer, they’re a gamble in typical British weather.

Maximise Warmth

Every extra degree of warmth translates directly into better growth and larger harvests. Black plastic mulch, cloches, fleece, and greenhouse cultivation all help. I’ve noticed that plants grown against south-facing walls, which retain and radiate heat, perform noticeably better than those in open beds.

Consider growing in black containers, which absorb heat from the sun and keep the root zone warmer. This simple trick has improved my yields considerably compared to terracotta or light-coloured pots.

Try Different Cooking Methods

Homegrown sweet potatoes often have a different texture and flavour to shop-bought ones, partly because they’re fresher and partly due to variety differences. I’ve found that roasting them at high heat caramelises their natural sugars beautifully. They also work brilliantly in curries, mashed, or even spiralised into noodles.

The smaller tubers that often result from British growing conditions are actually perfect for baking whole. Just scrub them clean, prick with a fork, and roast until tender. No waste, and the skin becomes deliciously crispy.

Save Your Own Slips

Once you’ve successfully grown sweet potatoes, save a few of the best tubers to produce next season’s slips. This is considerably cheaper than buying slips annually and allows you to select from plants that performed well in your specific conditions.

Store the tubers carefully over winter, then start the slipping process in late winter. I keep mine in a box of slightly damp sand in a frost-free shed, checking occasionally that they’re not rotting or drying out completely.

Companion Plant Wisely

The sprawling vines of sweet potatoes can provide beneficial ground cover for other crops. I’ve successfully grown them alongside climbing beans, where the sweet potato vines suppress weeds whilst the beans climb up supports. Bush beans also work well planted between sweet potato mounds.

Avoid planting near crops that need frequent harvesting or maintenance, as the dense vine growth makes access difficult. I learned this after planting them too close to salad beds that needed regular picking.

Frequently Asked Questions

Can you really grow sweet potatoes in the British climate?

Yes, you absolutely can grow sweet potatoes in Britain, though they do require more effort than regular potatoes. The key is providing enough warmth throughout the growing season, which typically means greenhouse cultivation or very sheltered outdoor spots. I’ve successfully grown them in Berkshire, and gardeners throughout southern England regularly produce decent crops. Northern growers will find greenhouses or polytunnels essential, but it’s definitely achievable. You won’t get the massive yields seen in warmer climates, but homegrown sweet potatoes have excellent flavour and the satisfaction of growing something a bit different makes it worthwhile.

What’s the difference between sweet potato slips and seed potatoes?

Sweet potato slips are rooted shoots grown from a mature sweet potato, whilst seed potatoes are small whole potatoes or potato pieces used for planting regular spuds. This difference exists because sweet potatoes and regular potatoes are completely unrelated plants from different botanical families. Sweet potatoes rarely produce seeds in our climate and are always propagated vegetatively from slips. You create slips by suspending a sweet potato in water or placing it in moist compost until shoots emerge, then rooting these shoots separately. It’s a different process entirely from the simple sprouted potatoes you’d plant for regular spuds, but actually quite straightforward once you understand the method.

How long do sweet potatoes take to grow from planting to harvest?

Sweet potatoes typically need 100 to 150 days from planting out to harvest, depending on the variety and growing conditions. Early varieties like ‘Georgia Jet’ mature faster, whilst standard types take longer. In British conditions, you’ll plant in late May or early June and harvest in September or October. This long growing season is why warmth is so crucial, as cooler temperatures slow growth considerably. I’ve found that greenhouse-grown plants mature noticeably faster than outdoor ones because of the consistently warmer conditions. You can harvest earlier if necessary, though tubers will be smaller. The key is harvesting before the first frost, which typically arrives in October in most parts of Britain.

Do sweet potatoes need full sun?

Sweet potatoes absolutely need full sun to produce a worthwhile harvest. They’re tropical plants that thrive on heat and light, and anything less than six hours of direct sunlight daily will result in poor growth and tiny tubers. I’ve tried growing them in partially shaded spots and the results were disappointing, even in warm summers. Choose the sunniest, most sheltered location available, ideally south-facing. In greenhouses, ensure the plants aren’t shaded by taller crops like tomatoes or cucumbers. The combination of full sun and warm conditions triggers tuber formation, and without both elements, you’ll end up with lots of leafy growth but little to harvest.

Can you eat sweet potato leaves and shoots?

Yes, sweet potato leaves and young shoots are entirely edible and actually quite nutritious. They’re commonly eaten in many Asian and African countries, though less well-known in Britain. The young leaves have a mild, slightly sweet flavour and can be used like spinach in stir-fries, soups, or steamed as a side vegetable. I occasionally harvest tender shoot tips during the growing season, which doesn’t harm the plant if done moderately and can even encourage bushier growth. The older leaves become tougher and less palatable, so stick to the young, tender growth. However, don’t harvest too heavily if you want a good tuber crop, as the plants need their leaves to produce energy for tuber formation.

Why didn’t my sweet potatoes produce any tubers?

Several factors can prevent tuber formation in sweet potatoes. The most common issue in British conditions is insufficient warmth, as sweet potatoes need consistently warm soil to trigger tuber development. Planting too early, growing in cold or waterlogged soil, or experiencing a particularly cool summer can all result in leafy plants with no tubers. Excessive nitrogen fertiliser also causes this problem by promoting foliage growth over tuber production. I’ve also seen cases where plants simply didn’t have enough time to mature before being harvested. Sweet potatoes need at least 100 days of warm growing conditions, and if you planted late or harvested early, tubers may not have formed. Finally, some shop-bought sweet potatoes are treated to prevent sprouting, and whilst they’ll produce slips, these might not grow properly.

How do you know when sweet potatoes are ready to harvest?

Sweet potatoes are ready to harvest when the leaves begin to yellow and die back naturally, typically in late September or October. However, in British conditions, you often need to harvest based on weather rather than plant maturity, as the first frost will kill the foliage and you want to dig tubers before this happens. I keep an eye on autumn weather forecasts and plan to harvest before any predicted frost. You can also harvest earlier if necessary, though tubers will be smaller. Unlike regular potatoes, there’s no test dig that works reliably, as tubers form directly under the plant rather than spreading outwards. If you’ve provided at least 100 days of warm growing conditions, you should have harvestable tubers even if the foliage still looks green.

Final Thoughts

Growing sweet potatoes in Britain requires working with our climate rather than against it. You’ll need to provide extra warmth, start with healthy slips, and maintain patience throughout a long growing season. The harvest might not match what commercial growers achieve in warmer regions, but there’s genuine satisfaction in producing these tropical tubers in our temperate climate.

I’ve found that managing expectations is important. You’re unlikely to harvest enormous tubers or massive yields, but the sweet potatoes you do grow will have brilliant flavour and give you something genuinely interesting to talk about with fellow gardeners. The process also teaches valuable lessons about season extension and warmth management that apply to many other tender crops.

Start small in your first year, perhaps with just three or four plants in containers. This lets you learn the quirks of sweet potato cultivation without major investment. Once you’ve successfully harvested your first crop and tasted the difference between homegrown and shop-bought sweet potatoes, you’ll likely find yourself expanding your planting each season. The combination of attractive foliage, easy maintenance once established, and delicious harvest makes sweet potatoes a worthwhile addition to any British garden willing to meet their warmth requirements.

Author: Megan Walker

Megan focuses on seasonal food, kitchen garden growing, and how households can reconnect with where their food comes from. Her writing blends practical growing advice with ideas for cooking and eating in season. With a passion for fresh ingredients and sustainable living, Megan’s articles help readers make the most of local produce while supporting British farms.