Growing potatoes
Potatoes are easy and satisfying to grow
Potatoes are easy and satisfying to grow, yielding a good harvest of eagerly awaited tubers below ground. An enormous selection of varieties is available to the gardener to choose from. These vary considerably in shape, size, colour, cooking and eating qualities, as well as resistance to common potato pests and diseases. It is worth trying a range of types to see which best suits your soil, and your tastes. Whatever you choose, grow your own organically - and they'll taste even better.
Potatoes are grouped according to their season of harvest i.e. earlies, second earlies and maincrop. In general, early varieties are lower yielding, require less space, and escape many of the diseases that affect the later harvested maincrop types.
Seed potatoes
Potatoes are grown from seed tubers that are certified free from virus and disease and are known as 'seed potatoes'. It is important to always buy in fresh 'seed' each year, do not be tempted to plant sprouted tubers from the kitchen as these are not certified and may introduce potato virus and disease to your garden. Tubers are either bought or received from your supplier in late winter/early spring and need to be stored in a cool dark place prior to chitting and planting out in March or April.
Chitting potatoes
Chitting - is the name for the process that encourages tubers to sprout before planting. Contrary to popular belief, chitting potatoes is not essential except for early varieties to produce an earlier maturing crop. If you buy tubers that have already started sprouting it is best to set them to chit straight away. If they haven't sprouted, they can be left in a cool dark place until you are ready to plant them or they begin to shoot anyway. To chit seed potatoes, place them side by side in a clean egg box or tray 'rose end' up (the end where tiny buds can be seen). Label the box with the potato variety and put in a cool light place for 4-6 weeks allowing the chits to develop. By putting them in a light place, the shoots will remain short, dark green and compact. Left in the dark, long, pale brittle shoots develop that can easily break off when planting.
Soil preparation
Potatoes grow best in a rich fertile soil, with plenty of organic matter incorporated and ideally, soil pH should be around 6.5 or lower. Never add lime before planting potatoes, as this can encourage scab. In spring, dig well-rotted manure into the top 30cm of soil. Use around one barrow load to 10 square metres of ground. If manure is unavailable, homemade compost, a general organic fertiliser (plus leafmould for water retention), or a proprietary brand of bagged manure can be used. Potatoes should form part of a crop rotation plan and should not be planted in the same ground for four years. For more information, please refer to our factsheet GG19 Crop rotation.
Potatoes can also be grown by using the no-dig method, for more information on how to do this, please refer to our factsheet GG2 No-dig gardening.
Planting
Dates will vary from year to year and around the country. The soil temperature should be at least 6°C (43°F). A good indication of this is when grass and weeds begin to grow, usually in March/April but it could be later for north and east areas.
Place the tubers rose end up in the bottom of holes or trenches that are 15cm deep. The shoots and leaves of potatoes are frost tender, so be prepared to protect them with cloches or fleece if frost is forecast. Earlies: Plant mid-March to the end of May with tubers spaced at 30cm, in rows 50-60cm apart. Second Earlies and Maincrop: Plant mid-March to the end of April with tubers spaced at 35cm, in rows 75cm apart.
'New' potatoes for Christmas: many mail order suppliers now sell late cropping seed potatoes. These are usually early varieties that have been held in cold storage and sent out in August. They do not require chitting and should be planted as soon as you receive them. Try varieties such as 'Carlingford', 'Maris Peer' or 'Vivaldi'. The plants will grow particularly quickly in the late summer warmth reaching a reasonable size by October and they can be harvested as late as Christmas day. As the leaves start to die down or, if the potatoes show signs of blight, cut the stems back to ground level and protect from frost with fleece or straw. As they are being left in the ground for a long period of time they may be more susceptible to blight and pest attack.
General care
Earthed up potatoes
- Potatoes can be 'earthed up' as they grow, this involves bringing soil up around the shoots to make a ridge. It helps control weeds, prevents the tubers turning green and gives some protection against tuber blight. Do it first when plants are around 15cm tall, leaving about 5cm of foliage showing. Earth up again just before the foliage meets across the rows. Plants can be mulched with a layer of hay, straw, leaf-mould or grass clippings. This will have the added benefit of conserving soil water. On a closer spacing, earthing up will not be possible, but the shade the plants provide each other will have the same effect.
- For the highest yield of good-sized tubers, keep the soil moist throughout the season. If additional watering is required, apply it to the soil and not the foliage. The addition of manure, compost and leafmould will all improve the structure of your soil and help it to retain moisture. Varieties of potatoes vary in their drought tolerance, so choose varieties that suit your soil conditions.
- Pests and Disease: detailed information about pest and disease prevention and control for potatoes can be found in our factsheet PC24 Potato pests and diseases, and on separate factsheets; DC17 Potato late blight, DC13 Spraing potato virus, PC20 Slugs and snails and PC28 Wireworm.
Harvesting and storage
- Early varieties: Will be ready at the end of May through to July, around nine to ten weeks after planting. Flowering is usually a good indicator that the tubers have reached an edible size, but not all varieties produce flowers. Dig up one plant or investigate with a trowel to see if the tubers are ready. They are best harvested as needed, leaving the rest to grow on. Most early varieties are not suitable for long-term storage.
Average yield: 5.5kg/3metre row - Main crop varieties: Depending on the variety, planting date and the growing conditions, these will be ready from mid July through to early October. Mature tubers with well-developed skins store best, so ideally they should be left in the ground for 2-3 weeks after the haulms have died back. Dig the crop carefully to avoid damage, on a sunny day if possible. Leave the potatoes to dry for a couple of hours on the surface before bagging up. If the crop is being damaged by pests, lift your potatoes earlier. Slug damage can increase dramatically in September.
Average yield: 9kg/3metre row
Store your potatoes in paper sacks (NOT plastic), in a cool, dark place and protect them from frost. Only store dry, undamaged potatoes. Check regularly and remove any rotting tubers.
Other useful factsheets:
Garden Organic members who read this factsheet also found the following factsheets useful:
- GG36 Grow your own potatoes in containers
- PC24 Potato pests and diseases
- GG19 Crop rotation
- DC17 Potato late blight
- GS4 Managing your soil
- DC13 Spraing potato virus
- GG2 No-dig gardening
- PC20 Slugs and snails
- PC28 Wireworm
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