Potatoes
Spuds can go in as part of a three-year rotation or as a section on their own, often used to clear ground for subsequent crops. The clearing doesn´t mean you just pop in the seeds into a grassland and come back in 3-4 months. It´s actually the constant earthing up of the potatoes that does the trick, as weeds don´t get a hold or get hoed up with the earthing. Dig over a plot roughly in autumn, adding manure as you go. This breaks up in the frosts and so when you are ready to plant, the soil is in good condition.  at a time when outside it´s still too cold to plant out.

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
Maincrop: 15" apart, 2'6" 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!
nodigspuds

mulch

soil

The HDRA has a factsheet here.

When to harvest:
Early earlies: 10 weeks
Earlies:12-14 weeks
2nd earlies: 15-17 weeks
Maincrop:18-20 weeks

Harvesting for storage
2nd early and maincrop only
Allow tops to die down naturally so skins are mature
If tops have been cut off for blight, leave 2-3 weeks before digging

Harvest early September at the latest
Best on a cool dry day
Leave on soil 2-3 hours to dry

Storing
Discard damaged and diseased tubers
Put dry potatoes gently into sacks (preferably paper to keep light out)
Store 2 weeks at 15oC then move to a cool, dry, frost-free place place for long term storage
Check every month or so for rotters

Fertilisers
Chicken manure! Very good, but really also need bulky organic matter for water retention as they need a lot.

Problems
This is where potatoes seem to win hands-down over other vegetables. There are so many things that can go wrong with a simple spud, all of which seem totally silly when you´ve just unearthed several pounds of flawless tubers accidentally growing in your compost heap...  Please go to the RHS, BBC or HDRA potato sites to get expert advice on the main problems: meanwhile here´s a précis of the main nasties.

Virus diseases
These tend to build up. The 1st year they are not usually a problem, not enough to affect yield. They become more of a problem if you save your own seed potatoes. The second year´s disease is usually much worse. Examples: potato mosaic virus (blotchy leaves), potato leaf roll virus (leaves roll inwards along the main vein).
Control:
-ALWAYS use certified healthy seed potatoes
If you do intend to save any, protect from aphids by growing in fleece.

Potato blight
Everyone knows about potato blight´s effects, at least if they´ve ever heard of the Irish Potato Famine of the 1800s. There are two types of blight - early and late. Though they appear similar at first look, the early blight is a different fungus and is not nearly as serious. Late blight can destroy a crop, starting with the foliage and finally destroying all tubers which the spores have come in contact with. Often this is when they are in storage, so it can devastate winter food supplies.
 Early blight occurs in the UK in late July/early August, and is not as damaging as late blight. Symptoms are dark blotches on the leaves with, on close examination, a "target" appearance with concentric rings. Plants go spindly and yellow.
Late blight has a much darker, shrivelled appearance. The spots really are black and it starts mainly on tips and edges of leaves. White mould can develop in patches. It overwinters in plant debris eg infected potato tubers in the soil ("volunteers"). Destroy all self-set potato and tomato plants growing on compost heaps. Live spores are wind-carried in hot humid weather. Infection spreads rapidly across fields and allotments from a single infected plant, so one person leaving in their volunteers can destroy everyone else´s potatoes. The spores are washed into the soil by rain, so once spotted, cut off all foliage and stems in a bad infection and compost in a hot heap, or burn. Leave the tubers in the soil for at least 3 weeks before harvesting them, to avoid infecting them with surface spores during lifting.
The likelihood of blight can be predicted: if there is a 48-hour period in which the minimum temperatures do not fall below 10oC, and which have at least 11 hours with a humidity of >89%, the blight will take off. So if it´s hot, muggy and classic thunderstorm weather for a couple of summer days, beware. You can treat it to a certain extent by spraying with a copper-based fungicide such as Bordeaux mixture, but it looks like the EU have got this in their targets to be banned so that won´t be around for much longer. Best thing is to grow earlies (they are harvested before blight becomes a problem) or resistant varieties such as Cara, Record, Santé, Valor or the excellent naturally-bred Sárpo red maincrops. I can speak for myself on the latter - I harvested my still-growing and blightless plants a bit too late in November and got a huge crop! Avoid Arran Comet, King Edward and Ulster Chieftain.

Scab
I can speak with experience on this one, too. Scab is angular spots of corky tissue caused by a virus. It´s harmless: you can scrape the raised patches off the tubers before cooking or cook them intact and rub off afterwards. But it is unsightly, and is pretty inevitable in very alkaline (high pH) conditions. You win some, you lose some (as in those same conditions you´re very unlikely to get clubroot on brassicas). Prevention is to dig in loads of organic matter before planting, use resistant varieties and water frequently. And don´t plant on limed ground!  Yield isn't affected but you need to peel more! Scab is worse on dry soils and chalky soils, so don't lime! Don't compost foliage, tubers, peelings or roots to prevent the virus spreading, though if you live in a chalk area like me, you might as well do it as you aren't going to get rid of the scab anyway…so you are best to learn to ignore it.  Avoid Majestic and Maris Piper.

Slugs
Keeled slugs, recognised by the yellowish line along the bottom of the back end, are the big problem here - they tunnel in and then excavate caverns in the middle of the tubers. Best solution here is to choose less susceptible varieties (I grew Mimi and dug up a load of hollow spheres so that won´t be grown again...), lift early or use a nematode-based soil drench. These only work for about 6 weeks but if you apply at the right time, they destroy all the early generation slugs so the population never gets out of hand later in the season. But this is an expensive cure.
Strategies for protection:
a) harvest before early September
b) Grow resistant varieties eg Santé, Romano and Golden Wonder
c) biological control
d) slug deterrants, traps, barriers
e) encourage predators such as frogs, hedgehogs and birds
 

Wireworms
These are clickbeetle larvae (copper coloured, three pairs of legs at the head end) and they will tunnel in and through tubers with ease. They tend to be worse where you´ve just dug over grassland to grow crops for the first time, and the best solution is to avoid growing potatoes in such areas for 3-4 years after first cultivation since the lifecycle is eggs laid in grassland and weedy soil, early -> midsummer. Larval stage is long – up to 5 years.. This rather goes against the `use potatoes to clear ground´ wisdom, unless the ground to be cleared is just full of annual weeds rather than grass. Cross section of damage is a long thin hole, which a slug can then use!
Control
a) Cultivate soil in winter to expose predators.
b) Lift potatoes in early autumn to limit damage
c) trap on spiked pieces of potato or carrot buried in the soil (also a good monitor of levels)
d) grow mustard as green manure as it is said to speed up the lifecycle.
 

Potato cyst eelworm
These are microscopic nematodes which infest the roots of potatoes and tomatoes. There are two types - golden and white eelworm.
They feed in the roots then the mated female blows up to become the egg case, a hard cyst with several hundred eggs inside. You see little globes on the roots with a hand lens, July-August. Colour varies from white teo black as they mature. Most hatch in the first year but they can remain dormant in the soil for 10-20 years, so normal rotation doesn't really help once you've got it! The cysts are stimulated to hatch by the chemicals secreted by potato or tomato roots.
Symptoms: plants yellow and die back prematurely, sometimes in patches. In severe infections, growth is stunted.
Control
a) Long crop rotation, 4-5 years minimum.
b) Encourage natural predators eg soil-dwelling creatures
c) Grow resistant varieties eg Cromwell, Kestrel, Santé
d) Use no-dig methods on badly infested land
 

Aphids
There is a potato aphid, but with over 500 types in the UK, pretty much any aphid can land on the foliage. They spread virus diseases.
Control
-Encourage ladybirds and lacewings
-Grow flowers eg calendula close by
-Wipe off infestations
 

Varieties I have grown
 I´m very much a learner with potatoes. But there´s only one way to learn...
Accent - first early, waxy. 4/5 tubers grew, not bad but will have to grow again to be sure. Not too much scab so worth another shot on that alone.
Mimi - mini cherry tomato-sized reds for salads. Plants grew fine but I think I got about three of the things that hadn´t been the local slug fast food restaurant. Lots of hollow spheres! Won´t grow again unless it´s in a tub, which I reckon it would be a perfect variety for.
Red Duke of York - now there´s a lovely tasting new potato. Definitely will grow these again.
Ratte - early main - takes the prize for giving me a waxy new potato salad on 2nd January, some 11 months after buying the tubers. I don´t care how funny shaped it is - this one I´m growing more of. Bit scabby in the chalk ground but not so I´d care, even in a skin-on salad.
Pink Fir Apple - late main - first boiling of these knobbly oddities I did with the also knobbly Rattes and the things all ended up the same colour so were hard to identify. Nearly the same taste too, but these are supposed to get more distinctive with storage. They didn´t last long enough! Shall grow again (but will cook separately!).
Estima - second early - grew 3 tubers of these because I love waxy baked potatoes. Got 6-8 small tubers off two plants and one enormous one from the third which I really enjoyed baking and eating. Suffered from being planted late though, so shall have another go on time next season and with hopefully more tubers. Not much scab!
International Kidney - see above for type! - Grown for last two years to see if I could outdo the bought ones for flavour, as a lot of folk in my family have commented that Jerseys don´t taste like they used to. Mostly successful in this - blind taste tested my Dad against Waitrose Jerseys and I won! But you really do have to dig early or they disintegrate. Recommend steaming them when this starts to happen.
Sárpo Mira, Axona and Tominia - these are the new blight-resistant cultivars from the Sárvari Institute, and though Tominia has been deemed too similar genetically to Mira to get a licence, Axona has just been granted one and it is going on sale with Mira as of early 2005 from Thompson and Morgan. I got 6 trial tubers at the HDRA potato day, and lost track of which ones were which after the foxes bit off the nametags. When dug (very very late - end October!), I got some huge tubers which lasted unsprouted until Christmas when they were ceremonoiusly eaten for Chrismas lunch. Very nice. Floury, fell a bit, can´t say I noticed any slug damage or even much scab, though the larger tubers did have hollow heart thanks to weird watering through the year. But then again the larger tubers *were* massive - over 6" long! Definitely going to be grown again in larger numbers.
 

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!