How to Grow Potatoes in Your Garden
ByWhere would we be without the humble potato? We eat new potatoes with butter and mint in late spring and roast spuds when it is cold and dark outside; few weeks pass by without potatoes appearing on our plates in one form or another. To the vegetable gardener, they are an easy crop that can be relied upon. Digging up the tubers is a job that the everyone enjoys.
Different types of potatoes
Potatoes come in a great diversity of sizes, shapes and colors, but they are classified as being either earlies or maincrops. Although both types should be planted at the same time, early types are ready to harvest much sooner than the maincrops, which tend to be larger and are the types that are stored over winter.
The best sites and soils
Potatoes can be grown on almost any deep, well-drained soil in a sunny site. It certainly helps if the ground is fertile, so is you can, add plenty of well-rotted organic matter in the autumn of the year before. Just ahead of planting, you can dress the ground with a general fertilizer, and be sure to rake well to break up any large clods. Avoid waterlogged ground, low-lying spots where frosty air could collect – because potatoes are very susceptible to frost – and light, free-draining soil, which can result in drought and scab unless you choose drought-tolerant varieties. Also leave a gap of about three years before growing potatoes in the same spot to avoid the accumulation of soil-borne pest and diseases.
Small crops of potatoes can be grown in large containers. Placed in a warm, sunny place under cover, this is a good way of getting an early batch of new potatoes. With a bit of preparation, you could even have new potatoes in the middle of winter.
Sowing and planting
Getting potatoes started couldn’t be easier. Just like in the supermarket, you buy potatoes off the shelf, but the difference is that the ones you need are special ‘seed’ potatoes – certifiably free from viruses. Usually they come in small bags, available from late winter, that may contain more potatoes than you need or have room to plant. In this case, share the purchase with a friend, or club in with others so that you can grow smaller quantities of a more diverse range of varieties. This way, you will discover much more quickly which varieties you prefer to eat, and which ones grow best in your soil.
Rather than eating your seed potatoes for dinner, you can start them into growth by sprouting or chitting them four to six weeks before planting. Set the tubers on end, with their ‘eyes’ uppermost, in egg boxes or seed trays, and place in good light in a cool room. Each potato will develop short green shoots, and the advantage of doing this is that it gets them into early growth, ready for the season ahead.
Begin planting your potatoes during early to late spring. You may want to get your earlies in first so that they crop sooner; another trick here is to increase the soil temperature with a covering of black plastic several weeks before planting, which accelerates growth. You can plant through holes made in the plastic.
The two methods of planting are to dig a trench or to plant in individual holes. Handle each sprouted potato carefully, so that you do not knock off any of the shoots, and plant 15cm (6in) deep. Space 30cm (12in) apart, with 60cm (24in) between rows for earlies, and 40-75cm (16-30in) for maincrops. Closer planting often results in smaller potatoes at harvest time.
Alternatively, in a well-lit and ventilated, frost-free greenhouse or porch, plant into large 10-litre (2-gallon) tubs that are at least 30cm (12in) deep, with one chitted potato to a container half-filled with potting compost. Cover with 10cm (4in) of compost and top up as the plant grows.
Some rare varieties are not available as seed potatoes, but as virus-free microplants. These should be planted out as any other type of seedling, after the last frosts, to the same spacing.
Cultivating the crop
Outside, as soon as the first shoots emerge, start the process of earthing up by drawing up soil around and over them to produce a rounded ridge, repeating at one- to two-week intervals until the ridge is around 20-30cm (8-12in) high. This kills weeds, helps prevent blight, and prevents the tubers being exposed to the light and turning green and poisonous. You do not need to earth up potatoes growing under plastic sheeting. Cover shoots with soil or fleece if frost threatens. During dry spells, give the plants an occasional but thorough watering to increase the yield. Plenty of water early on in the plants’ development will lead to initiation of many tubers and a heavy crop later on.
Look out for potato blight, which is a problem in warm, wet summers, although early crops are not usually affected as they are harvested before blight can strike. Potato scab is less serious; it causes raised, scab-like lesions, but they are just superficial and are easily removed on peeling.
Soil-dwelling slugs are a nuisance as they eat and burrow into the tubers. Use of the biological control Nemaslug, which is applied to the soil during spring and summer, can be effective. The presence of Colorado beetle is not common, but if you have it, it is often disastrous. Gardeners are required by law to notify the authorities. Plants that yellow, dry up and die from the bottom up may be showing signs of eelworm damage. These are quite common pests, and the best way to avoid them is to rotate your potato crop around the vegetable plot year after year and choose resistant varieties.
At harvest time
Lifting the first potatoes of the year is like digging up buried treasure. Choose a dry day. Earlies are ready when the flowers open or the buds drop, but first scrape away a little soil to check that they are large enough. Start lifting maincrops in late summer for immediate use. Carefully dig them up with a garden fork, taking care not to spear the tubers, and throw out any that are too small or excessively damaged or diseased, or have gone green through exposure to light – these are potentially harmful.
Small salad potatoes can be a bit fiddly to harvest. If you are intending to store the potatoes, leave them exposed to the air for a few hours so they can dry off. Mildly damaged potatoes should be eaten promptly. You can leave maincrop potatoes in the ground, digging as you need them, but be aware that the longer you leave them there, the greater the chance of slug damage. Slugs make small holes in the skins and burrow their way into potatoes, often causing extensive damage. Some of your potatoes may have scabbing on the skins; it is not serious and they just need to be peeled more deeply to remove the scabs. If the whole crop is affected, select a resistant variety to grow the following year.
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