Potato

Looking after it

Water: Potatoes need normal watering. Water them in dry spells, especially once the plants flower and the potatoes are forming. Steady moisture then also helps against scab. A pot needs regular watering even when it rains, because the leaves keep the rain off the compost. Feeding: Rich soil matters for potatoes, so grow them in ground improved with compost or manure. On poor soil, give a nitrogen-rich fertiliser the second time you pile soil around the stems. In a pot, mix a general fertiliser in at planting, or give a liquid feed after about six weeks.

Harvest and keeping

Dig early potatoes when the flowers open, once the potatoes are the size of hens' eggs. For maincrops you want to store, cut off the tops once they turn yellow. Wait 10 days, then dig. Start 30 cm from the stem so you don't spear any potatoes with the fork. Let the potatoes dry for a few hours and brush off the soil. Healthy, undamaged ones keep 2 to 4 months in paper or hessian sacks somewhere dark, cool and frost-free. Check them every few weeks and take out any that rot.

What can go wrong

• Blight. In warm, wet weather, brown patches spread fast over the leaves and then rot the potatoes. As soon as you see it, cut off the tops and take them away. Wait two to three weeks before you dig and grow resistant varieties.
• Scab. Rough, corky patches appear on the skin, but the potatoes are still good to eat once peeled. Water in dry spells while the potatoes form and don't add lime before planting. Grow resistant varieties.
• Green potatoes. Potatoes that get light turn green and are poisonous. Keep them well covered with soil and store them in the dark. Throw green potatoes away.