Potatoes are grown from seed potatoes that are usually grouped into three categories – first earlies, second earlies and maincrop. Potatoes do take up a lot of space but a polytunnel can be used to great effect to bring forward your first early potato crop and get the very earliest of first earlies in June. Potatoes can be grown either in the ground of your polytunnel or, to save space, in sacks or containers. Growing this staple at home is satisfying and very easy.
Your gardening year may well begin with chitting – leaving potatoes in a cool, light place to develop shoots before planting. While this is not strictly necessary, it will speed up the process and help ensure a good potato crop. Growing your own means that you will be able to choose seed potatoes according to your own tastes and cooking preferences. Some potatoes will be wonderful for roasting or baking, for example, while others are best for boiling or mash. There is lots of fun to be had in experimenting with potatoes with different colours, textures and tastes.
You can plant first early seed potatoes, sprout (or eye) upwards in your polytunnel from the very beginning of March to the beginning of April, depending on the weather and your location. The sprouts will appear above the soil after around a month – a little longer if the weather has been cold. Maincrops sown outside should usually be sown in mid to late April, depending on where you live in the UK. Traditionally, many people plant potatoes around Easter, particularly on Good Friday, though of course this is a variable feast.
Keep the soil moist, though potatoes will also like a soil that is loose and free-draining. Adding organic matter to the base of planting trenches before planting can help to retain soil moisture, as can adding a thick mulch. If a frost threatens when potato plants have just popped their foliage out from the soil then it can be a good idea to provide a little extra protection with straw or other mulches, horticultural fleece or cloches until the danger has passed.
Traditionally, soil is mounded around the stems of growing potato plants to protect the growing tubers from light. Begin earthing up when plants are around 20cm high. Organic mulches can also be used for this purpose. A good quality compost is perfect, as is seaweed, if you live by the sea, or bracken or straw, if you have access to those things. Organic mulches will also help to feed the potato plants as they grow and keep them healthy.
First earlies will be ready to harvest from June, second earlies in July and August and maincrop varieties from August to October. To see if first earlies are ready when plants are in flower, gently feel beneath the soil for tubers, trying not to disturb the whole plant. If the potatoes are large enough (about the size of a small hen's egg) then you can gently harvest your crop, as needed. Try not to leave any tubers in the soil as these can harbour disease and it is best to practice crop rotation.