Leading charity Garden Organic warns that the persistent wet weather is posing a real threat to the future of rare varieties of potato - plus, find out what else needs doing in the garden this week.
By Hannah Stephenson
The wet weather over the past couple of years has prompted reports of poor harvests, smaller and less tasty fruit and veg and claims that the nutrients the rain has washed away from the soil will affect the health value of our home-grown produce.
Among the crops worst hit in vegetable patches across the country is the humble spud, a staple of the British menu for centuries, whether boiled, mashed or chipped.
And while gardeners throughout the UK will be celebrating National Potato Day with events up until the end of the month, experts are now warning that gardeners must start to grow a mixture of varieties to stem the loss of crops to late blight.
Affected plants develop brown spots, especially around the edges of the leaves, the stems turn brown and potatoes develop scabby cankers that lead to brown patches inside the tubers which soon rot.
Bob Sherman, chief horticultural officer of charity Garden Organic, warns: "Rare types of potatoes are under threat. There isn't much that the amateur gardener can do to protect potatoes from blight.
"Late blight is a very rapidly evolving organism. It's not quite a fungus. It's quite closely related to seaweed, but it acts like a fungus. Spores flow about in the air, usually coming from old tubers left in the soil which haven't been harvested from the previous year because they've been missed.
"Most of the old varieties of potato are highly susceptible and even ones that were thought to be resistant have succumbed to new strains of the disease. We used to think that 'Cara' was blight resistant, but it isn't any more. A whole range of interesting textures and flavours from old varieties are under threat."
Incessant wet weather causes both disease and physical problems with potatoes, he continues. The tubers can't be lifted because the ground's too heavy and soggy.
"When potatoes get too much moisture, you might get one or two huge potatoes under the soil instead of a nice little clump of medium-sized tubers. The huge ones might be hollow inside or just not very tasty. Dry weather tends to enhance flavour, but wet weather reduces it."
Late potato blight has been the scourge of crops during excessive wet weather, he says.
However, some gardeners have turned to a resistant variety which is keeping blight at bay.
David Shaw, research director of the not-for-profit Sarvari Research Trust in North Wales, and his team developed a range of blight-resistant 'superspuds' known as Sarpos (pronounced Sharpo), first bred by the Hungarian Sarvari family.
Available in red, white and blue, from Thompson & Morgan and some garden centres, they are now being grown by gardeners who don't want the plight of blight.
"The disease evolves all the time, a bit like flu, so there's always a new strain. The Sarpo varieties David Shaw has been working with seem to be coping with all the changes that the disease is going through," says Sherman.
"Some of them will get signs of blight in the leaves, but not in the tubers."
He suggests growing a number of different varieties so that you're covered if the tubers, which are highly susceptible, succumb to blight.
"The other advice is to harvest earlier," he suggests. "You might sacrifice the weight of the potatoes, but the flavour will be good."
Alternatively, grow spuds in pots and bring them under cover later in the year. Blight usually strikes from July onwards, depending on the weather and which part of the country you live in.
Of course you can enrich your soil with plenty of organic matter, but if the weather's damp, it won't make any difference to blight, because the spores are carried in the air.
Covering the plants with tunnels or cloches may also not make a difference because potatoes need good air flow. If your tunnels are plastic, blight will thrive in the humidity. If you have a good-sized greenhouse, you may have more luck if you constantly remove the leaves showing signs of blight.
If the blight is widespread, take all the leaves off, which will mean a smaller crop, but at least you'll have a crop.
However, if you do remove leaves, don't lift any potatoes for at least two weeks afterwards, because the spores will still be on the surface of the soil, and if they come into contact with a tuber, they will affect it.
And if anyone has problems with slugs ruining their potatoes, Sarpo Mira and Sarpo Axona both have good slug resistance to go with blight resistance.
Try mixing crops, growing sweet potatoes or yacon, a perennial tuber from South America which looks like a potato and is not so susceptible to common pests and diseases.
:: Garden Organic's 20th National Potato Day is being held on January 27 at Ryton Gardens, near Coventry, in conjunction with Webbs Garden Centre. A full programme of activities and a list of all of the varieties on sale on the day will soon be available at www.gardenorganic.org.uk Best of the bunch - Snowdrop (Galanthus) The stems of these tiny winter gems emerge in mid-winter to produce delicate-looking white petals dangling down in their masses, either in woodland carpets or in pretty clumps here and there to bring welcome light to the scene.
There are more than 150 snowdrops listed and new varieties are being discovered all the time. They are perfect in drifts, happily colonising, their bulbs sub-dividing to thicken the clumps.
The most popular is Galanthus nivalis. All types prefer a moist soil, neutral or alkaline, and a position in partial shade. Some will flourish in complete shade.
They look lovely with other bulbs which flower simultaneously, such as aconites and Cyclamen coum, colonising under deciduous trees.
If you want a bulb which is slightly more showy, go for the double form G. nivalis 'Flore Pleno', 'Jacquenetta', one of the biggest snowdrops, or G. 'S. Arnott', whose flowers have a strong honey scent.
Good enough to eat - Chitting potatoes Seed potatoes can now be bought in large bags from garden centres and mail order outlets, but if you have limited space or just want to try out a few, hunt out the centres which sell loose tubers by weight.
Extra early varieties of seed potatoes should be 'chitted' before planting out. You chit them by laying the potatoes rose end (where most of the tiny sprouts are) on newspaper in clean seed trays or old egg boxes on a windowsill or in a frost-free greenhouse, in a light position but not in direct sunlight.
In a few weeks, the shoots will grow, gaining strength while the soil is still too cold for them to be planted outside.
Rub off all but the four strongest sprouts and when they have grown to around an inch, chitting is completed. Don't plant them out until next month, though, as the shoots will take time to develop.
Three ways to... Increase your soil's fertility 1. Use a pH test kit to find out if lime is needed to counter excessive acidity. If so, add lime in the winter to allow it to work its magic before the growing season.
2. Add organic matter such as well-rotted compost or manure to your soil in the winter and dig it in, to allow air and food to circulate through the soil.
3. Use organic mulches around established plants to add nutrients, suppress weeds and reduce moisture loss during prolonged periods of dry weather.
What to do this week :: Fork over vacant ground in beds and borders to prepare it for planting, if the ground is not too wet.
:: Mulch asparagus beds and clumps of rhubarb with well-rotted manure or compost.
:: Add lime to acid soil where brassicas are to be planted.
:: Prune outdoor vines :: Take root cuttings of Oriental poppies, phlox and verbascum.
:: Plant lettuces under cloches.
:: Position rabbit guards around the trunks of young trees if damage is likely.
:: Plant Jerusalem artichokes when the soil is neither frozen nor sodden.
:: Germinate seeds such as begonias and pelargoniums on windowsills indoors or in the greenhouse.
:: Cover the ground with cloches where early crops are to be sown, to warm up the area before the seeds go in.
:: Cut back newly planted cane fruits and complete pruning of established fruit bushes.
:: As cyclamen flowers go over, remove the stems by given them a sharp tug, which should remove the whole stem.
:: Remove any wet leaves or other debris clogging up herbaceous perennials.