Ok first thing I’m not an expert, most facts regarding sweet potatoes you can find out by googling. There isn’t however, a great deal specifically for growing them in the UK.
I started growing them from a few plants 3 years ago (which is expensive) and now I’ve moved on to plugs which I’ve grown on with good yield and size. They cost £15 for 12 plugs which I think is a good price especially if you go in with others. I had 12 plants this year and found it was too much, 6 is probably a good number to manage.
I tried to cultivate slips from a few runts I found leftover last year but they only produced roots. I’m determined this year to store the tubers better and select healthier ones to produce slips from. The difficulty is to provide enough warmth and sun light for them over winter. Ideally they probably need to be started in March or early April but sweet potatoes don’t store that long. If I fail then I’ll look to get hold of an organic chemical free sweet potato from a shop, watch this space!
Anyway, whether you have plants, plugs or slips plant them on in 10ltr pots as soon as possible with a mixture of normal compost and ericaceous. I find sweet potatoes prefer a slightly more acidic ph!
Keep these pots in the greenhouse/somewhere sunny and warm until mid to late May. Sweet potatoes like loamy, sandy slightly acidic soil so prepare a bed with this in mind. They also require depth, not for the tubers but for the roots, and space because the vines will spread.
I’ve read advice to plant them in mounds but I found as the tubers grow they poke out of the mounds especially with watering. They need lots of heat and lots of water. When first planted use fleece or cloche.
I created a hedgehog which would have been great if we hadn’t had the hottest summer on record! It did however slow down evaporation, a polytunnel would be ideal!
Even with a heatwave you can’t have too much heat with sweetpotatoes, you just have to make sure they are well watered. They also respond well to a feed of sulphate of potash. The leaves can be eaten like spinach and have more health benefits/vitamins than the tuber itself!
Harvest time is advised when the vines start to die back and before the first frost. My plants have never flowered nor died back. I harvest from the beginning of September as they are more or less ready, you can try and promote more growth by fleecing and feeding but if you have 12 plants you have to get stuck in.
When you harvest try and dig around the plant as much as possible and gently prise the plant up. Any damage to a tuber will prevent storage. The main tubers will be directly under the stem
When harvested unlike most veg they are not at their best, they need to ‘cure’ to bring out the sweetness. They need warmth (over 15c) and a bit of moisture for 4-5 days or even longer. An ideal place is an airing cupboard but not many households have these any more. A bathroom is a good place due to the humidity unfortunately there is probably a toilet as well!
The tubers I have harvested are now in potato bags in a cupboard. I’m due a slicer and dehydrator next week so I’ll be making chips/crisps. I have also blanched and frozen some, great for babies!
I have also started some off to produce slips, this will be an ongoing experiment of which I will post the results on twitter. Please post comments below if you have further advice. Thanks