Planting Seed Potatoes
Potatoes need a sunny site away from frost pockets.
First Early varieties should normally be planted from late March to mid-April in a narrow trench 12.5cm (5in) deep and spaced 30cm (12in) apart. The trench can be lined with compost or grass clippings and a sprinkle of slug pellets or other slug deterrents as keel slugs are often a problem. The rows should be 60cm (24in) apart.
Maincrop varieties should normally be planted from mid- to late April in a narrow trench 12.5cm (5in) deep and spaced 37.5cm (15in) apart. The trench can be lined with compost or grass clippings and a sprinkle of slug pellets or other slug deterrents as keel slugs are often a problem. The rows should be 75cm (30in) apart.
Second Early varieties should be planted somewhere between the two above.
It’s important to keep light away from the developing new potatoes as light turns them green and green potatoes are poisonous.
Growing Seed Potatoes
It is usual practice to chit the first early seed tubers first before planting; this means allowing them to produce sturdy shoots. Second early and maincrop tubers are usually treated the same way. As soon as you receive them from the Potato Day sale stand them rose end up (the rose end has the most eyes) in egg boxes or similar in a light, frost-free place. The tubers are ready to plant when the shoots are about 2.5cm (1in) long.
Once growing, when the stems are about 23cm (9in) high, start earthing up by carefully drawing soil up to the stems and covering to produce a flat-topped ridge about 15cm (6in) high. This can be done little and often or in one go.
Newly emerging foliage is susceptible to late frost damage. This can be prevented by earthing up the soil around the shoots or by covering them with fleece. A draw hoe or mattock is the best tool for this job.
Another method is to grow the potatoes under black polythene. The tubers are planted through the black polythene sheet. The advantage of this method is that there is no need to earth up and the new potatoes form just below soil level which means there’s no digging to harvest them.
It’s also possible to grow them in containers – or even strong black bin liners. Line the bottom 15cm (6in) of the container with potting compost and plant the seed tuber just below this. As the new stems start growing, keep adding compost until the container is full.
Keep crops well watered in dry weather; especially if growing in containers, this is vital once the tubers have started to form. A liquid feed of a balanced general fertiliser every fortnight can help increase yields.
Cropping your potatoes
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 early varieties wait until the flowers open or the buds drop. Maincrop varieties are best for storage, wait until the foliage turns yellow, then cut it and remove it. Leave for 10 days before harvesting the tubers, leaving them to dry for a few hours before storing. This prevents blight spores getting on the tubers being stored. Paper or hessian potato sacks are best for storing tubers as they eliminate light. Keep the sacks in a frost free garage or shed.
Potato blight: This is a common problem 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. There is no chemical control to stop blight, but you can spray with a protectant spray in June if it looks like it will be a wet one.
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’ or ‘Saxon’.
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.
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.
Slugs are a nuisance, as not only can they eat holes in the leaves, they also eat and burrow into the tubers. You’ll see the tell-tale slime trail of slugs on the soil around your crop, as well as on the leaves.
Remedy: There are many ways to control slugs, including beer traps, sawdust or eggshell barriers and copper tape. Experiment, as you may find some more successful than others. Slug pellets of powders based on aluminium sulphate or ferric phosphate are less toxic on other wildlife.