Sweet potato

We know the sweet potato has high levels of vitamins (A and B6 in particular), but only recently have varieties been developed which suit our climate and summer growing season. There are two types: the mealy-fleshed or dry ones, pale in colour and taste floury, rather like sweet chestnuts; and the soft fleshed sweeter types, which are often more orange or yellow coloured. These ones are high in beta carotene that transforms to Vitamin A in the body.

How to grow

Unlike ordinary or Irish potatoes, sweet potatoes need high temperatures (26-30°C).  They are best grown in a polytunnel/greenhouse with plenty of watering. Tubers will form where the stems touch the ground. The plant forms trailing vines up to 2.1m (7ft) or more. These can take over your plot if not tied up to encourage climbing!

  • Sweet potatoes are not propagated by planting individual tubers but by ‘slips’ or cuttings from the shoots which arise from the eyes on the tuber. Carefully unpack the slips (they can be very fragile) and plant around the edge of a wide pot containing a mixture of equal parts of sharp sand and a loam-based compost or well-rotted leafmould. Keep warm, with bottom heat and roots will soon develop. When you see white shoots emerging from the base of the pot, remove and separate the plants into individual 15cm/6in pots filled with a loam-based general-purpose compost.
  • Plant out the slips when the soil is at least 12°C. Over most of the UK this means no earlier than late May. Bury the plants deeply, with at least half of the stems covered to encourage tuber formation. Open ground is preferable to a pot, but they grow reasonably well in very large (over 34 cm diameter) containers.
  • Established plants can tolerate surprisingly wide swings in temperature, so don’t be put off even if your conditions are less than perfect. Fleece or plastic can be useful on cold summer nights. Minimum survival temperature is around 6°C, but protect from cold winds. Feed growing plants regularly using comfrey liquid, and water plants well in dry weather to keep them actively growing.
  • Tubers will begin to form from around August, but if you can, wait until the leaves have been touched by the frost before harvesting to achieve maximum cropping. The tubers won’t survive frost in the soil, so lift them before serious cold sets in.

Shop-bought tubers, even if they are sprouting, are probably not a variety which is suited to our UK climate. Instead, buy cultivars from seed companies that have been selected for growing in this country, such as ‘Beauregarde’, and ‘Georgia Jet’.

How to eat
Delicious in stews, curries and soups.  Roasted whole or as wedges, using spices to enhance the natural sugars.  Served cold in salads with citrus dressings and curd cheeses.

For a full list of multicultural vegetables see here. They all come from our innovative Sowing New Seeds and Growing From Your Roots projects, when Garden Organic worked with allotment holders of Indian, South American, East Asian, Afro Caribbean and African extraction.