Growing early potatoes in bags
You don't need a vegetable bed to grow potatoes. A few deep planting bags on a patio can give you a crop of new potatoes by early summer, and tipping out the first bag is one of the best moments of the gardening year.
Buying and chitting seed potatoes
Grow from certified seed potatoes rather than potatoes bought for eating, which may carry disease. Early varieties suit bags best because they crop quickly. From late winter, stand the seed potatoes in egg boxes in a cool, bright room, with the end that has the most eyes facing up. This is called chitting. After four to six weeks they should have short, sturdy shoots about 2 cm long.
Planting in a bag
Use a sturdy potato bag or tub that holds about 40 litres and has drainage holes. Put about 15 cm of multipurpose compost in the bottom, set two or three chitted potatoes on top with the shoots pointing up, and cover them with another 10 cm of compost. Water well. Early potatoes are usually planted in early to mid spring, but move the bags somewhere sheltered or cover them with fleece if a late frost is forecast.
Earthing up as they grow
When the leafy shoots reach about 15 cm tall, add more compost until only their tips show. Repeat this every couple of weeks until the compost is a few centimetres below the rim. Covering the stems gives the plant more room to form potatoes, and it stops tubers near the surface from turning green in the light. Any potatoes that do turn green should be thrown away, not eaten.
We have a habit for this stage that we call the kozatasor top-up: every weekend we look over each bag, add compost wherever stems or potatoes are showing, and water until it runs out of the base. Bags dry out quickly once the plants are large, so in warm spells they may need water every day.
Knowing when to harvest
Early potatoes are usually ready about ten to twelve weeks after planting, often around the time the plants flower. Push a hand into the compost at the side of the bag and feel for a potato the size of a hen's egg. When most are that size, tip the whole bag out onto a sheet and pick through the compost. Eat them soon after harvesting, while they are fresh and full of flavour.