Return of the sweet potato

By Richard Wright

Published on Friday, May 04, 2012 - 11:09


Return of the sweet potato

The tuber.

GARDENINGSWEET potatoes were a device employed by my wife as a way of getting both our daughters interested in proper veg.

My wife had obviously boned up on sweet potatoes, spoon-feeding them to the girls because they are much more vitamin C and calorie rich than garden potatoes.

As the name implies, they are also much sweeter.

So, wind the clock on a good few years and we have hardly touched a sweet potato but that is all set to change.

Young Bella is now a healthy 13 year old and, like us, has not touched a sweet potato for a long time but she soon will, courtesy of one of her friends, Amber, whose father, Steve Prust, thought he would have a go at growing them.

I previously knew absolutely nothing about sweet potatoes and made the assumption, probably like most other gardeners, that sweet potatoes were closely related to our garden potato when, in fact, they are only distant cousins.

The sweet potato is, in fact, a close relative of our bindweed and the flower will tell you that morning glory is also in the family. That will also give you a hint that several of the species are poisonous.

Sweet potatoes can be grown from shop-bought veg but they should be washed because often these have been treated with a compound to shop them shooting.

It is probably best to go to one of the seed companies because they have cultivars which are more suited to our climate — the imported sweet potatoes having come from tropical climes.

It is the shoots that should be planted to produce the next generation and these are supplied by the likes of Thompson & Morgan as TM65, said to be especially suited to this country but still requiring high temperatures.

The Royal Horticultural Society tells me sweet potatoes are best grown from cuttings, which are not, in fact, rooted and technically called slips. You would normally buy them mail order from late April onwards. When they arrive, pot them immediately into small pots of multi-purpose compost or, indeed, cardboard cylinders.

I gave Steve a length of cardboard carpet roll in which to culture them and, in return, he kindly gave me a couple of 'slips’ (cuttings), which have picked up after a shaky start.

Keep the compost moist, using tepid water, so as not to shock them. Cover the pots with a clear plastic bag or place them in an unheated propagator until they root.

If you want to have a go on the cheap, as an experiment, now is a good time. Place a tuber in moist vermiculite, perlite or sand in a warm propagator or airing cupboard to encourage sprouting.

Remove the shoots, with a sharp knife, when they are two or three inches long and pot them into small pots of compost and root them in a warm propagator. Treat cuttings from overwintered plants in the same way.

If grown outdoors, and that can be problematic in our climate, sweet potatoes need moisture-retentive, free-draining soil, in a sheltered, sunny position.

Use black polythene to warm the soil and suppress weed growth by laying it over the soil several weeks before planting as the soil starts to warm up.

Grow the plants on in a bright, frost-free position, in the greenhouse or on a sunny windowsill, until late May until early June, potting on as necessary. Harden off before planting outdoors, in slits through the polythene.

Cover with cloches or fleece — the temperature lift makes all the difference because they crop best between 70F and 80F.

Grow sweet potatoes in a glasshouse in large tubs, grow-bags or the glasshouse border, transplanting from the pots once they have produced plenty of roots.

The foliage can be trained up string, canes or trellis. Any good growing medium is satisfactory and a feed ever fortnight with Tomorite or something similar is recomm- ended.

Tubers take four to five months to mature and are best lifted once the leaves turn yellow and die back. They need careful lifting to avoid bruising.

They rot if frozen and are hard to store so consume them promptly.

Sweet potatoes can be boiled, roasted or cut into chips and the shoots and leaves can be cooked and used as a spinach substitute.

All in all, it is not a trouble-free crop and one which I probably would not have bothered but for the very kind gift.

I’ll let you know whether the effort was worth it.

Should you wish to give it a try, these are varieties worth considering.

Beauregard Improved: Similar to the tubers on supermarket shelves. Tubers have distinctive salmon-orange flesh, which is well flavoured and sweet.

T65: This has red-tinted skin colour and creamy white flesh. Reliable and vigorous, with good sized tubers.

Georgia Jet: This is early maturing, productive and reliable throughout the UK. Flesh is deep orange and very tasty.

O’Henry: A compact variety. The tubers develop as a cluster beneath the foliage. Ideal for containers.

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