Best Way to Grow Potatoes
Potatoes may not seem like natural candidates for container growing, but you can harvest delicious early newfrom your patio if you have space for a few large pots or boxes.
As long as potatoes remain a staple food they will be an attractive prospect to gardeners, and though you may not be able to harvest a bumper crop from containers, you can certainly enjoy the finest quality. Potatoes are categorized under first early, second early and maincrop grades, and though the choices are restricted for container growing, there are a few varieties of first earlies which produce good results. The second early and maincrop potatoes are best suited to growing in open ground – you would have to give a considerable amount of space to maincrops and it is hardly worth it as they are among the least expensive of market vegetables.
Even for the smaller new potatoes, you need to have space for a group of large pots- the minimum practical size is 12in (30cm) deep and 8in (20cm) across. Large wooden boxes make ideal containers for potatoes. You may be able to find crates used for storing and transporting vegetable produce; if they are solid at the base, remember to punch holes in them to allow drainage. It is because this crop needs a relatively large area for growing that it is best to site the containers on a patio or balcony out of the way of domestic traffic, but potatoes can be grown indoors if that is your only option.
Selecting potatoes for container growing Potatoes are not grown from seed but from seed potatoes, tubers which have been specially selected, bred and grown to produce plants capable of developing crops of edible tubers. You cannot use ordinary potatoes which have begun to sprout; these produce at best a poor-quality, slow-growing, limited crop. Seed potatoes can be obtained from markets, garden centres and specialist growers and are usually sold by weight. Make sure that they are certified disease-free and conforming to standard growing regulations.
The varieties which I can most strongly recommend for container growing are Arran Pilot and Pentland Javelin. These both have white flesh; Arran Pilot is a kidney-shaped potato while Pentland Javelin is oval. Home Guard and Foremost are good choices, both white-fleshed and oval.
Sprouting tubers and planting
The seed potatoes are not planted straight into; they have first to be sprouted allowed to produce shoots from the potato ‘eyes’. Lay them in a shallow box and leave them exposed to the light – they do not need a covering. Position each tuber with some of the eyes uppermost, to allow them to sprout freely. I do not recommend cutting seed potatoes into pieces unless they are very large, which is unlikely with these varieties; a cut surface increases susceptibility to rotting.
The tubers require only a cool or moderate temperature while sprouting, but must not be exposed to frost. The sprouts should be sufficiently developed for the seed potatoes to be planted within four to five weeks. Check their development periodically; if they are spindly and pale, they are not getting enough light. Ideally, the shoots should be short and stout.
Regular planting time for potatoes is early to mid spring; container-grown crops can have a head start, but do not plant them outdoors if frosts are still likely. Fill the containers with soil-based growing mixture, preferably with some added silver sand, leaf mould or peat, or a little of each. Horse manure is a good addition if you can obtain it, and a handful of bonemeal is beneficial. It is best to plant up the containers in situ, as they will be heavy once filled with soil.
Plant the tubers with the sprouted eyes uppermost. Cover them with soil to about 4in (10cm) deep and firm the surface. Water the containers moderately; the soil must not be allowed to become saturated, as waterlogging rots potatoes very quickly.
A potato crop thrives best in moderate temperatures. Outdoor conditions during spring should suit the plants quite well, unless there is an unexpected cold snap. Maintain moderate watering through all stages of growth, increasing the water supply only on very hot days in the summer months. The top growth of the potato plants may be self-supporting, but if the stems tend to lean or fall, support them by tying them to canes.
You may be aware of the process of ‘earthing-up’ garden-grown potatoes. This simply means drawing up soil around the base of the plant to prevent light from reaching the newly-formed tubers. If the potatoes are exposed to light they become green and are inedible – a green potato is poisonous – and should this happen, do not attempt to use the potatoes in cooking. Adapt the earthing-up process to your containers, drawing up soil from the sides of the pot towards the base of the plant, or adding a little more growing medium if necessary.
Potato plants eventually come into flower, and the time to harvest is after the flowers have faded and the foliage has begun to turn yellow. Small new potatoes taste particularly delicious, but if you prefer to let them increase in size, simply leave the plant in the container a little longer. When the leaves have lost all green colouring, however, the potatoes cease to grow, as the plant is no longer manufacturing food for the tubers by the process of photosynthesis.