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How to grow potatoes in the ground
Preparing the site
When growing your own potatoes choose an open position in full sun on fertile, well drained soil. Avoid soil where potatoes have grown for two years in succession as this will increase the risk of disease. A slightly acidic soil is preferable but not essential as potatoes will tolerate a wide range of soils. When growing potatoes on more alkaline soils, apply sulphur to the top of the potato ridge after planting. Applying sulphur maximizes the yield and deters skin blemishes like Common Scab that are particularly troublesome in alkaline conditions.
Begin preparing the planting site well in advance (November/ December) to allow the soil to settle before planting potatoes. Remove all weeds and dig the site thoroughly and deeply, lifting out any large stones, and incorporating plenty of well rotted organic matter and high potash fertiliser.
Chitting Potatoes
Seed potatoes, particularly earlies and second earlies, benefit from 'chitting' prior to being planted. This process encourages strong shoots to sprout over several weeks to encourage faster growth and heavier crops once they in the ground. From late January/ February, ‘chit’ your seed potatoes by setting them out in seed trays, shallow boxes or empty egg cartons in a cool, bright, frost free position (10C/ 50F) to allow them to sprout. You will notice that the immature 'chits' are all at one end (called the rose end). Place the rose end upwards. Sturdy 'chits' will form and should attain up to 25mm (1”) in length.
Planting
Planting times are largely dependent on weather, soil conditions and regional variations but the table below is a general guide. Dig a trench to a depth of about 10cm (4”) and place the seed potatoes into the trench with the rose end facing upwards. Fill the trench with soil to cover the potatoes. An application of potato fertiliser can be scattered
Aftercare
It is important to ‘earth up’ potato crops as the shoots emerge above ground, to protect them from frosts which blacken the shoots and delay production. Simply draw some soil over the top of the shoots to cover them again.
First early and second early crops particularly require plenty of water during prolonged dry weather especially when tubers are starting to form.
When the stems reach a height of 23cm (9”) above ground they should be earthed up again to prevent tubers near to the soil surface from turning green. Harvesting.
Lifting times will vary depending on the growing season, weather conditions at harvest time and the size of tuber you want. However the table above provides a rough guide for each crop type. Start to harvest first earlies as 'new potatoes' when the plants begin to flower, approximately 10 weeks from planting. Tubers will generally become larger the longer their growing period.
Maincrop varieties are usually left for at least two weeks after the leaves and haulms (stems) have withered, to allow the skins to set. Cut down the stems with secateurs to just above soil level as the leaves wither and yellow, or if they show signs of blight. After harvesting, leave the tubers on the soil surface for a few hours to dry and cure the skin. Once dry store them in paper or hessian sacks in a dark, cool but frost free place. Avoid storing in polythene bags as potatoes will 'sweat' and rot.
Second Cropping Potatoes
In the UK, second cropping potatoes are best planted outdoors in early August and no later than he end of August. If planting in a protected environment (e.g. in a polytunnel or greenhouse) planting can be delayed by a week or so but must be planted by the end of the first week of September. Planting second cropping potatoes later than this is likely to produce disappointing results. There is no need to pre-chit the seed potatoes - this will happen quite naturally after planting.
'Ping-pong ball' sized tubers should be ready for harvesting approximately 10 to 11 weeks after planting. Cut back the stems to just above ground level. Tubers can be dug up as required, with the others being left in the ground. However, they must be protected from frost so it is worth covering them with a thick layer of straw and/or sacking.
Second cropping potatoes can be lifted up to Christmas time. However, leaving them in the ground for this length of time does make them more susceptible to blight and pest attack (e.g. slugs, wireworm).
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