Sweet potatoes are in the same family as convolvulus and have the same sort of flowers as the garden flower. Sweet potatoes are a herbaceous perennial vine, but are grown as an annual to harvest the sweet potato roots.
Having been domesticated at least 5000 years ago in the tropical parts of South America, they thrive best where the average temperature is 24 C, there is abundant sunshine, warm nights, a long growing season and absolutely no frost. This is a tall order for the UK, and they will certainly need to be grown in a greenhouse or poly tunnel in the North of the UK to have any chance of success.
They are cultivated from sweet potato “slips”, which can be produced by partly immersing a sweet potato in a glass of water, placed in a sunny window at a warm temperature. Roots can sprout under the water line, while “slips” or shoots grow from eyes on the surface of the sweet potato.
When the “slips” are some 7 cm long, they should be potted up in a good potting compost until they are well rooted.
When well rooted and when the temperatures are warm enough, they can be moved to their final growing position in a large pot in a warm, sunny place.
If your growing conditions are warm enough and you intend to grow outdoors, plant the rooted slips through black polythene, to cut down weeds and help conserve moisture.
Warning. On no account plant out these sub-tropical plants before the last expected date for frost in your area. This could be mid May for the mildest areas such as Southern coastal areas, and early June in the North of the UK. Even then, provide cloche or fleece protection for the first few weeks as cold nights and winds will cause plant damage. Gardeners are regularly caught out by late frosts occurring during the traditional cold period known as “The Ice Saints”, usually just before mid May. Remember, one night of a late frost will kill your sub-tropical plants!!
The foliage forms long vines and will twine for several metres if support is available.
Keep well fed and watered until they die-down naturally in late Autumn when the nights get colder. Harvest the tubers and keep them in a frost free place.
Pests and diseases. Red spider mite can be a problem in the hot conditions of a greenhouse. Spray regularly with water or a proprietary insecticide.
Suggested varieties of Sweet Potatoes supplied as slips.
Beauregard Improved. Tubers tend to be smaller than T65 but have that distinctive salmon orange flesh with a sweeter more pronounced flavour.
Georgia Jet Flesh is more deep orange colour of excellent flavour. Claimed to be early maturing and a good cropper
Sweet Potato T65 The skin colour is reddish but with a creamy white flesh. Reputed to be the most reliable and vigorous variety producing good sized tubers.
Sweet Potato O’Henry. Cream skinned and fleshed tubers with a rich flavour. The plant habit differs to our other varieties in being more compact and bushy and the tubers develop as a cluster beneath the plant for easier lifting. This would be more suitable for container growing.
Bought-in slips tend to be quite expensive and unless you have ideal conditions, you may be disappointed with the quantity of sweet potatoes harvested at the end of the year. You can also experiment with growing your own slips starting with a shop bought sweet potato, but the variety may be best suited to tropical conditions.