Potatoes

Sow

Potatoes are grown from specially prepared ‘seed’ potatoes (or tubers). These are just like potatoes you buy from the supermarket, but they’re certified virus-free. You can buy seed potatoes from late winter onwards. You then start them off indoors by letting them sprout, before they are planted.

Preparation before planting

It’s important with earlies, and a good idea with maincrops, to ‘chit’ the seed potatoes before planting. This means allowing them to start sprouting shoots.

Stand them rose end up (the end with the most small dents, or eyes) in egg boxes or trays in a light, frost-free place. The potatoes are ready to plant when the shoots are about 3cm (1in) long. With early potatoes, rub off the weakest shoots, leaving four per tuber.

Grow

Potato plants need ‘earthing up’ as they grow, to protect early shoots from frost damage and ensure the developing potatoes aren’t exposed to light, which turns them green and poisonous.

It’s a simple process – once the stems are about 23cm (9in) tall, draw soil up around them, creating a ridge about 15cm (6in) high. As the stems grow, repeat the process several times. The final height of the ridge should be 20–30cm (8in–1ft).

Keep the plants well watered in dry weather – particularly once the tubers start to form. Maincrop potatoes benefit from a nitrogen-rich fertiliser around the time of the second earthing up.

Plant

Planting time varies, depending on the type of potato you’re growing:

• First earlies – around late March

• Second earlies – early to mid-April

• Maincrops – mid- to late April

The timing also depends on where you are in the country – planting should be slightly later in colder regions and can be earlier in milder ones. And when growing in containers, you can plant earlier too.

Potatoes need a sunny site. Avoid planting in a spot prone to late frosts, as the newly emerging foliage is susceptible to frost damage in April and May. 

Prepare the ground, ideally the previous autumn or winter, by digging in plenty of organic matter such as garden compost or well-rotted manure.

The traditional planting method is to dig a narrow trench 12cm (5in) deep. Space the tubers 30cm (1ft) apart for earlies and 37cm (15in) for maincrops, in rows 60cm (2ft) apart for earlies and 75cm (30in) apart for maincrops. Apply a general-purpose fertiliser at this stage.

How to plant early potatoes

Gardener, blogger and allotmenteer Bryony Willis, shows you how to plant early potatoes.

Other planting methods

Potatoes can also be grown under black polythene sheets. The tubers are planted through slits in the polythene. The advantages of this method are that there is no need to earth up, and new potatoes form just below the surface, so there’s little or no need to dig.

Small crops of potatoes can also be grown in large, deep containers. This is a good way to get an early batch of new potatoes. Fill the bottom 15cm (6in) of the container with potting compost and plant one seed potato just below this. As the new stems start growing, keep adding compost until the container is full.

Common problems

Potato blight

This is a common disease in wet, warm summers. The initial symptoms are a rapidly spreading brown watery rot, affecting leaves, and stems. Tubers can be affected too, and have a reddish-brown decay below the skin, firm at first but soon developing into a soft rot.

Remedy

Unfortunately once blight starts, it is very difficult to stop. You can remove blight-affected leaves, but removing too many leaves will damage the plant’s ability to grow. Earthing up potatoes provides some protection to tubers. Try blight resistant cultivars or stick to earlies which are usually harvested before blight strikes.

More info on Potato blight

Potato blackleg

Potato blackleg is a common bacterial disease which causes black rotting at the stem base. Initial infections cause stunted growth and yellowing stems. If tubers form, the flesh may be grey or brown and rotten.

Remedy

Remove and destroy infected plants. Rotate crops. Buy resistant varieties such as 'Charlotte', 'Pixie' and 'Saxon'.

More info on Potato blackleg

Potato scab

This disease causes raised scab-like lesions on the potato surface. It does not affect the taste of the potato, and is easily removed on peeling.

Remedy

There is no control for scab, and you usually won’t know anything is wrong until harvest time. Scab can be worse in dry weather, so keep potatoes well watered. Don’t store any potatoes with scab.

More info on Potato scab

Potato rot

Potato tuber rots are a frequent cause of losses prior to, or after, lifting. Significant problems often follow a wet growing season, particularly if the tubers are then lifted from wet soil.

Remedy

Use good quality, resistant certified seed tubers when planting and harvest when the soil is neither wet nor very hard and dry. Store in cool, dry conditions.

More info on Potato rot

Harvesting

• First early potatoes should be ready to lift in June and July

• Second earlies in July and August

• Maincrops from late August through to October

With earlies, wait until the flowers open or the buds drop. The tubers are ready to harvest when they’re the size of hens’ eggs.

With maincrops for storage, wait until the foliage turns yellow, then cut it down and remove it. Wait for 10 days before harvesting the tubers, and leave them to dry for a few hours before storing.

Recipes

Nigel Slater suggests roasting young potatoes – although this may sound like an odd thing to do, it brings out their fudgy texture and crisp, papery skins.

Varieties