Until recently, sweet potatoes were still seen as quite an exotic food in the UK. And while the British public seems to have taken well to the sweet potato, attempts to grow it among gardeners are still few and far between.
While the “traditional” potato is grown in numerous gardens and allotments across the nation, growing sweet potatoes is still quite an unusual skill. If pressed, very few people could even describe what a sweet potato plant even looks like.
I’m here to day to change all that. Over the last three years I’ve grown a number of sweet potato plants, having a range of results. In this article I’d like to discuss what I’ve learned in that time, in the hope of helping anyone to grow their own sweet potatoes at home.
Buying Sweet Potato Slips
Anyone who has grown traditional pototoes knows that the typical starting point is buying some “seed potatoes”. These are tiny “baby” potatoes, which are chitted and then planted. Soon enough the foliage starts to grow.
Sweet potatoes, however, are started in a rather different manner.
While the general method of growth is similar – that a sweet potato will give off foliage – it is unusual to purchase whole sweet potatoes for this purpose. Instead, the growing stems are severed from the parent potato and grown on. These rootless stems are known as “slips”.
While it is easy to purchase pea seeds or baby corn plants from garden centres, sweet potatoes are still quite an unusual crop. In addition to this, the slips require quite specialist care, which makes them far less suitable to be sold in retail. As a result, it’s almost certain that you’ll need to order your sweet potato slips via mail order.
Personally, I tend to buy mine from Thompson & Morgan. They aren’t cheap, but the quality tends to be excellent.
These are normally ordered early in the year, allowing the supplier to gently raise enough slips, before they are sent out to customers. Most sweet potato slips are sent out in late April or early May, so it is often some months between you ordering and actually receiving the slips.
Take note, therefore, that if you want to grow sweet potatoes you should order early, as many suppliers quickly sell out early in the season.
The slips are sent out by post, often wrapped in damp paper. On arrival they can look quite sad, with their leaves crumpled and their stems floppy, but if properly cared for they will soon recover. The key, when receiving sweet potato slips, is to give them these conditions as quickly as possible.
Leaving your slips to fester in their package until the weekend is unlikely to end well. Fortunately, Thompson & Morgan send out an email as they dispatch sweet potato slips, so you get a day or two of warning to get prepared and keep an eye out for the package.
So your long-awaited sweet potato slips have finally arrived. What now?
The journey from slips to busy, healthy plants consists of two different stages. The first of these is getting the slips to produce roots. The second is to gently coax them into healthy, luscious plants.
On arrival at your home, sweet potato slips will look far from impressive. The first time I received any, I wondered if I’d made a terrible mistake, having spent a fair amount of money and ended up with what looked like a few half-dead stems. But take heed – sweet potatoes are fighters and they’ll soon recover.
The key to starting your slips off properly is to provide them with an abundance of sunlight and water. What you’ll want to do is grab a suitable container such as an old jamjar or a drinking glass, and fill it with fresh water. The slips tend to be quite long (12+ inches) and thin, so a container that is tall and narrow tends to be better than a shorter, broader one.
The very same day your slips arrive, place them into your makeshift “vase” of water, and pop them on the sunniest windowsill in your home.
Now the wait begins.
Over the next few days you’ll see the tiny slips start to recover. Those flattened leaves will re-inflate. The stems will firm up. And at the bottom of the slip, below the water line, small roots will start to show.
When your plants are fully recovered and a generous root system is evident – something that takes a few weeks normally – it’s time to ease into the second phase. Here we take the recovered slips, and actually plant them in compost.
For ease, I tend to fill a large flower pot with top-quality compost, and plant all my slips together in it. This pot is further left on the windowsill for some weeks. During this time, the root system of your sweet potatoes will grow still further, and you’ll likely observe the plants starting to grow.
Once the plants are green and healthy, and are showing signs of decent growth, they can be prepared for their final planting area.
Growing Sweet Potato Plants
By now your sweet potato slips should have turned into healthy plants over a period of weeks. By mid- to late-May, when the frosts have passed and your plants are established, its time to plant them in their final fruiting area, where they can happily ramble away all summer long.
In recent years I’ve tried growing the adult sweet potato plants both in the greenhouse and outdoors, and have generally had a better crop when planted in my vegetable plot. This saves space in the greenhouse for other more sensitive food plants.
Sweet potatoes are ramblers, rather like many squashes, and will slowly crawl their way over the soil surface. They tend to appreciate the sunniest and warmest position you can provide, while I have found that water-logged soil tends to stunt their growth.
As your plants will likely be growing all the way from June through till late summer, it is also worth considering how to keep them weed-free during this time. Having experimented with weed-suppressing matting, I have found it to be tremendously successful, greatly cutting down on my workload.
The process I currently adhere to is therefore as follows…
Select a sunny area of your garden, offering well-drained soil. Carefully weed the ground, then lay down your weed matting. Holes are then cut in the matting every 12-18″, and one of my sweet potato plants is inserted. Once all my plants are in the ground, they’re watered generously and pretty much left to their own devices.
Over the last few years I have found that sweet potatoes tend not to be affected by too many pests or diseases – a recent attack of blight which killed off my tomatoes left the sweet potatoes untouched, and caterpillars tend to steer clear. They also tend to cope well with dry conditions, so very little additional watering is required.
Lastly, with the weed control matting in place, no regular weeding is required either. This therefore makes sweet potatoes one of the easiest crops of all to grow, as they require little or no ongoing maintenance.
Once they’re planted you can essentially forget about them, letting them do their thing until the weather starts to turn in the autumn.
Harvesting Sweet Potatoes
Eventually the solder weather will roll in. Your vegetable plot will empty out and winter will beckon. This is the time of harvest your sweet potatoes – as late in the season as you can. As a rough guide, I tend to harvest mine around late September/early October, at the same time that I’m harvesting my butternut squashes.
Harvesting is simple. Just peel back the weed-control matting to give you full access to the ground, then gently insert a garden fork some 6-12″ away from the base of your plants. Gently lever them out of the soil, and you should find an impressive collection of home-grown sweet potatoes below ground level.
As the soil is often moist and heavy at this time of the year, there is a chance that some of the roots could have fallen off during this process, so dig around to make sure you haven’t missed any.
Pop the plants on the compost heap (they won’t survive without the roots) and take your sweet potatoes indoors to enjoy!
Storing Sweet Potatoes
Sweet potatoes will store for an incredible period of time if done properly. Many of mine stay fresh for months on end, giving me a nice long season of eating sweet potato chips and hearty soups. The key is to keep them in a dry, cool environment. If they’re allowed to sweat, or get too hot, you’ll find their shelf life declines considerably.
For best results, therefore, place the potatoes into trays, making sure that they’re not touching, then pop them in a frost-free garage or shed. Check on them regularly throughout the colder months to make sure none are rotting and you should be able to enjoy the fruits of your labour right up to Christmas time.