Choosing
After dry summers seed potatoes may be in short supply, so allways order and buy early. In some years, you might not be able to get the cultivars (varieties) you want if you wait too long before buying. Seed potatoes tend to be available from garden centres and from mail order suppliers from January.
Avoid using ware or eating potatoes as there is a risk that you will be planting virus-infected tubers that will give a disappointing crop. Tubers you have grown yourself are also likely to carry disease.
Certified seed sold by seed suppliers, garden centres and DIY superstores is guaranteed to be virtually free of pests and diseases.
Types
Early potatoes mature in June and have a subtle flavour and texture, quickly lost after they are lifted - enjoy as soon after harvest as possible. Good cultivars include: ‘Accent’ (early, flavoursome and relatively trouble free) and ‘Red Duke of York’ (a handsome red potato with a floury texture). If you can only grow one potato, choose the latter.
Freshness is also important in salad potatoes. ‘Ratte’ matures in early autumn, but can be gathered from late-summer, with waxy, firm, pale yellow, oval tubers.
Where space is limited, second-early potatoes lifted in July and August can make way for follow-on crops such as leeks. ‘Charlotte’, with waxy, firm flesh suitable for salad use, and ‘Lady Christl’ are good choices.
Supermarket maincrop potatoes, sold from September until spring, are so cheap it is only worth growing those noted for superior flavour. This includes ‘Pink Fir Apple’, with finger-like tubers of firm, full-flavoured flesh. Maturing as late as October, it may need spraying against blight. ‘Picasso’ is resistant to potato cyst nematode, crops heavily and is good for baking.
Chitting
Once home, seed tubers are best 'chitted' or sprouted. Unpack and lay the tubers out in a single layer in a tray with the 'rose' end uppermost. This end has the most eyes or buds and sprouts will arise from these. Some suppliers offer 'pre-chitted' seed.
Keep
the trays of tubers in a cool but frost-free place with at
least moderate light, such as in an unheated room. Direct
sunlight is best avoided. Sprouts will form within a few weeks.
The tuber is therefore ready to grow away as soon as planted.
Tubers can be laid out to chit from January onwards, but planting
should be delayed until March in sheltered and southern areas
or April in less favoured districts. Earlier plantings can
rot in the ground or the shoots can be frosted off on sharp
nights. By this time the sprouts should be about 5cm (2in)
long and dark coloured. Longer thinner sprouts are caused
by excess heat or too little light or both, and tiny sprouts
suggest conditions are too cold. Chitting takes about six weeks.
If the weather is unsuitable for planting, tubers can be left to chit further, even into May, without too much loss of crop.
Although unsprouted tubers can be planted, the chitted ones benefit from their flying start. Early cultivars will crop earlier and more heavily if chitted. You can help the process by rubbing off all but the four strongest sprouts so that the tuber's energy is diverted into a few really strong shoots that form new potatoes as early as possible. Second early and maincrop potatoes also benefit from chitting but they don't need thinning of sprouts. Chitting later cultivars results in earlier foliage before blight or drought strike and they mature earlier and can be gathered before slugs damage the tubers.
Microplants
Microplants produced by a laboratory propagation method called micropropagation are also disease-free planting material. Grow these in the greenhouse until the risk of frost has passed and then plant outdoors.