How to grow potatoes

It’s better not to use shop-bought potatoes for seed because they are often treated with a chemical that inhibits sprouting. You will be much surer of getting a good crop if you order certified disease-free seed potatoes from a seed company or buy them at a farm supply centre.

Use the seed potatoes as they are, or cut them into 50g pieces, each about the size of a large walnut. Make sure that each piece contains at least one eye. You will get best results if sprouts from the eyes are about 2cm long.

Cure the seed pieces by spreading them out in a bright, airy place until they dry slightly and their cut surfaces harden. 

Potatoes require acidic soil, tolerating soil with a pH as low as 4.8. Do not plant them in areas that have recently been limed.

An excellent way to prepare the soil for potatoes is to spread an 8-12cm layer of well-rotted manure or rich compost over the area to be planted; this will serve to enrich the soil and to improve drainage. 

As soon as the ground can be worked, plant the seed pieces in furrows 10cm deep, 8cm wide, and about 90cm apart. Set the pieces 30cm apart, with eyes facing upward, and cover with about 8cm of soil.

About three weeks after the seeds are planted, sprouts will push up through the ground. As the vines grow, mound up over them with earth, leaves, straw, or compost to keep the developing tubers covered. Potatoes that are exposed to sunlight turn green and develop a toxic substance called solanine. If there is any risk of night frost, cover with a layer of straw or newspapers.

It is not necessary to fertilise the plants again during the growing period, but be sure that the soil around them remains loose and free of weeds. To do this, cultivate gently with a hoe.

You can start harvesting at about the time the potato flowers bloom, seven to eight weeks after planting. Push aside the earth at the base of the plant until you see the new growth, and carefully pick off some of the small potatoes.

These are the highly valued “new” potatoes, which you can boil and eat in their skins. Leave some potatoes to grow to full size.

When the plant foliage begins to wither and die down, the potatoes are full-grown. At this time, dig the tubers from the soil with a spading fork. Although you can leave potatoes in the ground for a time after the foliage has died, you should dig them up before the first heavy frost.

If you want to store potatoes, gently brush off any soil and put them loosely in a ventilated, covered container to dry for a few hours. (Never expose potatoes directly to sunlight.) Store them in a dark, cool (3-4°C) place.