Read guest blogger Richard Barrett’s advice on avoiding potato blight
Why I like to grow potatoes
The potato started life as food for the poor but has risen in value to become a favourite vegetable for everybody. I like to grow my own potatoes because I then know in what conditions they have been grown. Commercially the plants are often repeatedly sprayed with fungicide to safeguard against blight and then the foliage is knocked back by herbicide before harvest. This seems a poor environment for food crop.
So I have my own potato patch, it is light soil that does not waterlog, has lots of sunshine and is free of tree roots. Also it the land around slopes away, so is not a frost pocket where the cold air can flow into. The soil is alkaline, this can mean the tubers may have scab on their skins, but this diminishes when potatoes are grown regularly in the same soil as a micro-organism builds up that prevents scab. That does not mean that I do not use crop rotation but often the same patch is used every other year. I make lots of cold compost, where garden waste is processed in a big heap and left to its own devices for a year. So I apply the compost to ground early in the year for the rain to wash the goodness in, any course particles can be raked off to go back into the new heap. Although cold compost contains viable weed seeds, this does not matter because the leafy potatoes will smother any weed seedlings. I will also apply seaweed meal to the soil so my plants have extra minerals for growing, these will hopefully enter the potato tubers too. Keeping the vegetable plot free of weeds and in good cultivation keeps pests like wireworm and slugs at bay.
From St Patrick’s Day onwards I start planting the seed potatoes in variety, first earlies first and then so on to maincrop, completing the process by Easter. I plant to a depth of six inches and leave all well alone until I see small sprouts of potato leaves appearing on the surface of the soil. Then in stages I start to earth the sprouting leaves forming a trench either side of the row, if frost threatens, then I earth up completely covering the new shoots, otherwise they can be left just showing. Early planting is worthwhile as the potatoes stand a good chance of cropping before blight emerges in late summer.
There are two types of blight, early blight which discolours the foliage inhibiting the plants to grow, but far worse is late blight which appears as black/brown necrotic spots in a humid August/September gradually defoliating the plants and then entering the tubers which rot from within, making the potatoes inedible.
There is much written within seed catalogues about which varieties to choose. The best advice is to grow a range of varieties, that way you can reap the benefits of potato growing whatever the weather. Early blight is a nuisance but tolerable, picking off poor leaves can help the plant. When late blight appears you must cut all the foliage away to soil level immediately, yet there are some varieties such as Sarpo Mira that can resist blight, so the leaves of such can be left growing.
What is not mentioned in potato literature is the difference between thick and thin skinned potatoes. The tubers of thick skinned variety like Cara can be left in the ground where they remain fresh and full of moisture, then lifted as required for the kitchen. Whereas Orla is a tasty variety with beautiful foliage that resists early blight, but it is thin skinned and must be harvested as soon as possible or the tubers will be damaged by pests such as slugs and wireworm. Whatever varieties you choose, or method of cultivation, the potato is a very rewarding and nutritious vegetable to grow.