Potatoes are classified as being either earlies or maincrops. Early potatoes are ready to harvest much sooner than maincrops and are what we call new potatoes. Maincrop potatoes are in the ground a lot longer, they have a better yield and produce larger tubers
Plant March -April- May
Once planted, 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.
Earthing up protects newly emerging foliage from to frost damage . It also protects developing new potatoes from light. Light turns tubers green and green potatoes are poisonous.
Keep crops well watered in dry weather; the vital time is once the tubers start to form. A liquid feed of a balanced general fertiliser every fortnight can help increase yields.
It's vital with earlies and a good idea with maincrops to chit the seed potatoes first before planting; this means allowing them to start sprouting shoots. Stand them rose end up (the rose end is the one with the most small dents in the skin, or 'eyes') in egg boxes or similar in a light, frost-free place. The potatoes are ready to plant when the shoots are about 3cm (1in) long.
Follow these guidelines for planting times of seed tubers:
- First earlies: around late March
Second earlies: early to mid-April
Maincrops: mid- to late April
The traditional way is to dig a narrow trench 12cm (5in) deep. This can be lined with compost or even grass clippings for a better crop. The seed tubers are spaced 30cm (12in) apart for earlies and 37cm (15in) for maincrop varieties in rows 24in (60cm) apart for earlies and 75cm (30in) apart for maincrop. Sprinkle slug pellets or other slug deterrents between the tubers as keel slugs can be a problem.
Potatoes need a sunny site away from frost pockets - the newly emerging foliage is susceptible to frost damage.
The other method is to grow the potatoes under black polythene. The tubers are planted through the black polythene. 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.
Small crops of potatoes can also be grown in large, deep containers, and this is a good way of getting an early batch of new potatoes. Line the bottom 15cm (6in) of the container with potting compost and plant the seed potato just below this. As the new stems start growing, keep adding compost until the container is full.
First early potatoes should be ready to lift in June and July, second earlies in July and August, maincrops from late August through October.
With earlies wait until the flowers open or the buds drop; the tubers are ready to harvest when they are the size of hens' eggs.
With maincrops 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. [attachment=0]potato.jpg[/attachment]