It is essential to guard and protect against late frosts with the early crop. Any forecast or thoughts of frost, and the rows should be protected overnight with horticultural fleece. Newspapers will also suffice, but will need to be anchored down.
The same method of growing is the same for early and main crop potatoes. Unlike most vegetable crops, they will need no additional feeding, though light mulching with grass mowings is beneficial.
It is important to keep plants earthed up, for the sun gets to the new tubers, they will turn green. Green potatoes are poisonous!
With the early crop, you can sift through the soil with your fingers, taking the largest tubers and then leaving and covering the smaller ones to grow on. This can be carried out once the potato plants have started to flower.
Once the potatoes have started to flower, they should be watered well. This will increase the size considerably and also ensure plump tubers.
The early potatoes should be cropped as and when necessary for the kitchen. Simply leaving them in the ground for an extra week will increase the yield considerably. In any event, they do not store well, so leaving them in the soil is the best option. Once the foliage dies down, then it is time to finish the cropping.
The maincrop can be dug and harvested once the foliage has died. Once dried off, they are best stored in paper or hessian sacks.
Potato blight can be a problem. It is a fungal type disease which has serious implications for future growing of potatoes in the same area.
It is prevalent in damp humid conditions, and affects the main crop rather than the early potato crops. It is also known as late blight. It normally shows after the middle of summer, and in wet conditions. There is little in the way of good chemical control or cure, but preventative sprays with a vegetable fungicide is thought to help.
It can be recognized with the leaves turning brown, then watery and black in most cases. This is not the normal dying-down of the foliage. In wet weather, it may be possible to see the white fungal growths at the bases of the stems. If your potatoes become affected, then cut off all the foliage at or near to ground level, and burn all debris. Leave the potato tubers in the ground for around two weeks which will help harden the skins, then harvest.
You should not plant the same area in the following year.
As early potatoes are the most valuable crop, and as they are not generally affected by potato blight, you may consider growing only them, and not bothering with the main crop.