BACK

Potatoes

Solanum tuberosum

INTRODUCTION

An allotment essential, grown on virtually every plot in the country. First cultivated in Peru and Chile over 7000 years ago, the humble Potato is the fourth largest produced vegetable in the world.

Potatoes are classified into 'earlies', 'second-earlies' and 'maincrop'. First and second-earlies are less prone to disease and are for immediate use. Maincrops are produced for longer-term storage and are heavier yielding, but are susceptible to associated diseases such as blight. There are hundreds of available varieties with more being added each season, allowing for a year-round supply.

Soil Preparation

Potatoes will grow in most soil types but very alkaline soils are less desirable. Potatoes are also suited to growing in containers if space is at a premium.

The site should be open, sunny, frost-free with fertile, moisture-retentive soil.

Organic material should be added well in advance of planting, like most root crops, Potatoes dislike freshly manured soil.

Add an organic Potato fertiliser prior to planting. A list of suppliers can be found in the Product Directory

Sowing & Planting

First and second earlies should be 'chitted' (pre-sprouting of potato tuber) 6 weeks before planting to encourage earlier harvests, this is not required for maincrop varieties.

Planting can be made during early spring onwards when the risk of frost has passed.

Maincrop Potatoes can be planted a little later.

Rake soil to a fine tilth and plant tubers into a trench or holes at least 15cm deep with 30cm (12 inches) between tubers. Allow 60cm (24 inches) between individual rows.

If growing in containers, use a pot size of at least 20 litres half-filled with multi-purpose compost, with 2 tubers planted into each one.

Growing & General Cultivation

Keep growing crops weed-free. Once established, Potatoes have a dense canopy of foliage that will help suppress weeds.

As the crop grows, 'earth up' to encourage heavier yields and to protect potatoes from going green if exposed to light.

Container grown Potatoes should be filled with compost to the top of the pot as soon as shoots appear.

Potatoes will not tolerate frost, earth up or cover with fleece if frosts are forecast.

Potatoes require regular watering once established to ensure good size tubers and heavy yields, especially if growing in containers.

Pests & Diseases

Potato Blight is probably the most serious Potato disease you will encounter. It spreads rapidly in warm humid weather, particularly during late summer and as a result, affects maincrop more than early varieties. It shows as brown patches on the leaves, resulting in total loss of all foliage and affecting tubers. To prevent, keep Potato foliage as dry as possible and spray with a systemic fungicide. As an alternative, use blight resistant varieties such as Sarpo 'Mira' or 'Carolus'.

Slugs can be a problem later in the season when they burrow into the tubers underground. The issue becomes worse the longer they are left in the soil especially in wet conditions. Use nematodes such as 'Nemaslug' or grow slug tolerant varieties such as 'Kestrel' or 'Golden Wonder'. Lift crop in good time. Do not store affected tubers.

Potato Cyst Nematode (Eeelworm) will cause foliage to turn yellow and overall growth will be severely checked. Eventually, all foliage will die. Grow resistant varieties such as 'Vales Sovereign' or 'Pentland Javelin'. Do not grow Potatoes on affected soil for at least 5/6 years.

Potato Scab shows as a corky scale on the skin but does not affect the Potato and can be removed by peeling. It is more common on dry or very alkaline soils. To prevent, keep crop well-watered, avoid over liming soil and grow resistant varieties such as 'Nicola' or 'Nadine'.

Harvesting

Potatoes should be ready for harvesting by mid-summer onwards. In general, earlies take about 10 weeks from planting until maturity, 2nd-earlies approx 12-13 weeks with maincrop varieties maturing after 16-20 weeks.

Earlies are ready as soon as the flowers have died off. Maincrop are better left in the ground until the autumn for the skins to harden which will aid long term storage.

Lift using a fork but take care not to damage any tubers. Use immediately any tubers that get 'speared' by the fork as these will not keep.

Potatoes grown in containers can be simply tipped out. Cover any spare tubers with compost to stop them from turning green.

New Potatoes are at their best fresh but will store in the fridge.

Maincrop Potatoes should be dried and kept in paper or hessian sacks and stored in a frost-free garage or shed until required. They will store through until the following spring.