I AM off to Kelso tomorrow for the 22nd Potato Day run by Borders Organic Gardeners. This will be the first year I haven’t either been organising the event or offering advice as the council’s home composting adviser, so I’ll be free to concentrate on choosing which of the hundred or so varieties I’d like. Everyone has to decide the type of potatoes they want – waxy or fluffy, salad, chipper or baker – and what space they have. Timing is just as important – when to plant; how to arrange a good succession of potatoes; and when you want or need to harvest the crop.

Potatoes fall into three categories: first earlies, second earlies and maincrop. These groupings relate to the length of time it takes varieties to mature, not, as many people think, the order of planting. First earlies take 10-12 weeks to grow; second earlies 13-15 weeks; and maincrop 16-20 weeks.

To add to the confusion, some varieties, such as Belle de Fontenay and Orla, are classified as first earlies by some mail-order firms and garden centres but second earlies by others. They could be both: it depends how long you leave them in the ground. A wonderful, waxy, fresh Red Duke of York becomes dull and floury when left to grow on, so could be described as either kind.

Remember, small is always beautiful. If you have little space you’ll probably choose first earlies, reckoning that the new potato taste is what matters. For a longer season of first earlies, stagger the planting, leaving a fortnight between a first and second planting.

As ever, the weather determines planting and, to a lesser extent, harvesting time. Although potatoes cope with most soils and growing conditions, they will only grow well when soil temperature is at least 7C. Tubers may rot when the ground is cooler. The plants are frost-sensitive, so the shaws or foliage should only appear above the ground after the risk of frost has passed. Plant around a month before the usual last frost, and cover any emerging shaws with soil or fleece if late frost is forecast.

Pests and disease also affect what and when to plant. Ever since the Irish potato famine in 1846, our potatoes have been ravaged by that direst disease, late potato blight, Phytophthora infestans. It turns spuds to mush. Tiny brown circles on the leaves and withering round the edges are often hard to spot at the beginning but, within a week, the shaws collapse in a rotting heap. The disease then spreads down to the tubers and turns them to a watery mess.

The disease strikes any time from mid July onwards, with timing depending on where you live and weather conditions. It thrives during a muggy, wet spell.

Here in the Borders, I start anxiously scanning the crop for the first signs of disease at the end of July. I also outwit the disease by growing second early varieties that are ready by early August.

There are plenty of different second earlies. Nicola is, in my book, the tastiest salad potato, closely followed by Jazzy, and it keeps its flavour well into winter. The Phureja group – Mayan Gold, Mayan Queen and so on – make perfect potato wedges, and you don’t even need to peel them. And Marfona is a good baker.

With their unique blight resistance, I also do a few Sarpo maincrop potatoes. The new maincrop baker, Alouette, is reputedly just as resistant. I’ll see.

You also foil our old friend the keeled slug by harvesting at this time. The biological control Nemaslug is quite effective, but the grass paths between my raised beds are slug heaven, so I like to harvest my tatties before the slugs do.