Digging out potato tubers is one of the most rewarding things gardens have to offer. Children in particular are surprised at seeing unearthed tubers that almost miraculously become chips, mash or baked potatoes.
Happily, potatoes are very easy to grow. Seed tubers are placed in good garden soil, ideally fortified with a bucket of compost for every square metre, in a sunny spot, about 10cm deep at 30cm intervals in rows 60-70cm apart. Seed tubers are not really seed of course but small tubers grown to be free of diseases. Supermarket potatoes can be planted and often a fair crop results – but the yield is often poor from plants with crinkled or mosaiced leaves, the sure signs of viruses.
Potatoes grow well in containers filled with material from peat-free growbags or garden soil mixed 50:50 with growbag compost. Plant one tuber per 60cm half-filled diameter container. Fill the container to near the top as the plant grows.
Seed tubers are offered as earlies, second earlies and maincrop. The second earlies and maincrops can be stored for winter use but earlies are usually consumed in summer. Some are sold as salad potatoes, generally second early in maturity, but are best eaten in summer.
Seasoned potato growers buy early seed potatoes in February and place them in a cool reasonably light place – an unheated spare room for example – and let them sprout (chit). It takes six weeks for small sprouts to form. Although it is highly advantageous to chit early potatoes to advance the harvest date, there is some advantage to chitting later ones so they mature a little earlier before slugs and blight disease occur when it turns wet in late summer. However, good crops, possibly heavier ones due to a longer growing season, result from planting un-chitted seed.
Potatoes are capable of very heavy crops and although not essential, fertiliser used as the manufacturer suggests greatly enhances yields.
Early potatoes are typically planted from mid-March in the south, but are liable to emerge before the frost season finishes in May. The shoots are frost sensitive, requiring protection on cold nights by hoeing a little earth over them or using newspaper.
Second early and maincrop potatoes are planted in mid-April – the frost risk will be low, but not absent, by the time they emerge. As the stems grow, soil is drawn with a hoe around them until the foliage meets in the row in early summer. At this stage, the potato patch is a series of ridges. The tubers form in the ridge shielded from light that turns them green and inedible. Covering with black plastic or a thick layer of compost is also feasible instead of ridging but plastic is not sustainable and slugs can multiply in compost.
Tubers are initiated slightly before the flowers open and once the flowers are fully open it is time to check for tuber formation – start to dig plants when the tubers are hen’s egg size. They swell rapidly but gradually lose their succulent new potato flavour so harvest freely.