Categories of potato
`Early´ earlies - potatoes such as Swift and Rocket, crop in 10 weeks from planting.
First early - can be planted mid-end March in my area (up to end April in more northerly or frost-prone areas), and are ready to dig in some 12-14 weeks ie from mid-June. Only produce small, new potatoes and they don´t store, but worth it! Some varieties are very fast, but tend to suffer in taste compared with some others. All, however, are likely to be nicer than supermarket spuds!
Second early - late March planting, and in 15-17 weeks, so July harvesting.
Early maincrop - late March, and crop in 18-20 weeks, digging mid-end August
Maincrop - late March, and 20+ weeks: September harvest.
When I first decided to grow potatoes, typically I picked one of the most awkward varieties in that it´s variously described as first early, second early and early maincrop. It confused me utterly, not knowing when or how to plant, but finally got it sussed. If you do find a variety with different descriptions, it´s usually borderline ie 2nd early/early maincrop, or has two very different characteristics depending on how it´s grown. For instance, the International Kidneys I chose are grown as first earlies in Jersey and known as the Jersey Royal when they come from there. They are a very waxy salad and new potato. But if they are left in the ground longer, ie around 18+ weeks, they go floury and often `fall´ when boiled (and seed companies get a lot of complaints that they sent the wrong seed potatoes!).
Next ask yourself what kind of potato you like. Do you like mashed, baked, roast or new potatoes? Do you spend a fortune every spring when the first new potatoes come into the shops? Decide what you like and then get hold of a potato seed catalogue and preferably a guide such as that written by Alan Romans (available from Thompson and Morgan). You will be able to find the ones which fit the bill, and have a chance of growing on your soil type.
Next you have to get hold of some. Mail order is all very well, but most seed companies sell huge minimum numbers of tubers which are much too large for the average gardener to grow more than one. Best idea is to go to a Potato Day in January or February: these allow tubers to be bought individually and often cheaper than in the catalogues. I went to the HDRA potato day at Ryton and bought sets of five tubers for 13p each, so was able to try six or so kinds for both taste and suitability. They also gave lectures on growing technique, and my notes are being used to make sure I get this section right!
Heritage potatoes: these are the very old potatoes which are high on taste but low on sales, being very specialised. Unfortunately thanks to EC regulations, unless a variety is licensed (at a high cost) the seed potatoes may not be sold. This can be got round by the companies selling microplants, grown in a sterile medium from a few cells and therefore guaranteed to be disease free. However, they then have to be coddled like tomatoes, and potted on until big enough to plant in containers or grow bags. The first years' tubers can then be used to grow a proper crop in open ground the next year.
Chitting: Alan Romans thinks chitting is unnecessary, as it's been found to accelerate the ageing process of the tubers and so the crop may be brought forward and so not be as large as otherwise possible. However, chitting is essential for first earlies and probably second earlies - they need to be accelerated. Place tubers, once bought, in a cool, frost-free, light place, upturned in egg boxes or seed trays of compost. You shouldn´t get the spindly shoots that are so often the result of leaving potatoes too long in a dark place! They should be compact, with dark green rosettes of leaves. Plant when the shoots are an inch (2.5cm) long, though if the weather isn't fit, it's better to wait than to lose the lot.
Planting time: Soil should be reasonably warm before planting, and the technical definition of the right time is when the soil is 8oC at 4" below the surface for 3 consecutive days! The end of March is usually around the right time, though if you warm the soil up with cloches or plastic, it is possible to plant in February. If the weather really is terrible, you can plant up to May. I can verify this: I chitted everything on time once, then didn´t get round to planting the tubers until a month after I ought to have done. I had to wait a bit longer than everyone else, but they got there...The latter is not recommended, however, as by the time the late plants are nearing maturity, there is a great risk of blight. To beat this, plant as early as possible. The soil should not be waterlogged. Plant all types together: they only differ in harvest times. (Except forced earlies under cloches.)
Trench planting is the simplest method - just dig a trench, fill halfway with well-rotted manure and place the tubers on top of this. Fill in the trench: there should be 2" above an early and 4" above a maincrop tuber.
Spacing: Earlies: 12-15" apart, 15-20" between rows
Earthing up: This is frost protection for shoots, weed control and prevents tuber greening. Also, it reduces blight infection of tubers if it should hit. You can mulch with grass, clippings, paper, straw etc if you don't want to earth up. It probably doesn't make the yields any higher!
There´s also a no-dig method for growing organically, which gives lovely clean potatoes and none of the earthing up. Mow any weeds on the plot, manure the surface. Place the potato on the soil surface with spacing as above, but if it's very early in the season or in a frost-prone location, dig a small hole and bury slightly. Cover with a 6" layer of straw or hay. Just cover the rows at first, leaving walking space between them. Once the tubers are through, add more to fill in, and top with grass clippings to lightproof it. Straw mulch is very effective against blight. You must wait for the soil to be moist before planting or the mulch seals in dryness. Advantages: easy to harvest: you just move the mulch to one side and pick off tubers. They don't suffer from scab, and it's good way of clearing weeds without too much digging! Disadvantages: mice can get to the tubers!
The HDRA has a factsheet here.
When to harvest:
Potato cyst eelworm
Varieties I have grown
Next season: I´m going to try the better ones above again, with more Rattes and fewer Int Kidneys, and add in Kestrel which gets glowing reports from just about everywhere. And anything else that takes my fancy at the Potato Day!