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Thursday, March 15, 2012

How to Grow Potatoes

Potatoes are the most productive staple crop you can grow in Ireland. They have nutritional value of about 750cals/kg and a surprising amount of protein. They need minimal care and attention, no processing other than cooking. Yields of 30 Tonnes/ha are normal in conventional agriculture and on a garden scale this is possible too. That is 3kg/sqm, (or a half stone), or 2,250cals, roughly enough food for an average person in a day. This means that by planting an area of 400sqm or 40mx10m (less than 1/10th of an acre) you could have enough calories for the year.
Potatoes like a rich fertile soil with plenty of organic matter, an even supply of water, and a good weeding early in the season. The flavour of potatoes varies with soil condition more than any other crop that I know of. Potatoes grown with too much fresh manure, seaweed or chemical fertiliser have poor flavour. I think the best potatoes are grown in newly broken up grass land, without any applications whatsoever. They are also good when grown with well composted manure. Some people have a problem with wireworm in grass but it isn't a problem here.
The most important factors when planting potatoes are getting them under the surface of the soil, keeping them weed free and earthing up. A good organic soil will hold enough water for potatoes and they should never need watering. Watering very dry soil, (in a tunnel for instance), causes potatoes to crack a a sudden watering causes the tubers to expand so fast that the skins burst open.
On a garden scale you can just place them on the surface of the soil and pile compost and mulch on top, but it is important to keep a heavy mulch on top as if the new tubers are reached by light they will go green, and green potatoes contain poisonous substances. Alternatively you can prepare the soil by digging or rotovating and push them under the soil. The deeper you push them the less earthing up you will have to do, but the slower they will come up. I like to get all my potatoes in about now and if all the ground is not prepared, I dig a trench, put as much good compost in it as i can spare, and then the seed potatoes. I cover them up roughly and as they begin to come up I fork out any weeds between the rows. As soon as possible they need to be earthed up. This means moving soil between the rows, against the stems, to cover them but without covering too much of the leaf area. Bringing soil around the plants kills the weeds, and encourages the stems to produce tubers. It also covers tubers close to the surface preventing them from going green.
I space early potatoes about 30cm apart in rows 60cm apart and maincrop potatoes 40cm apart in rows 90cm apart.
Early potatoes come out of the ground from June to August so there is time to grow another crop after them. Leeks or spring cabbage make a good crop to follow potatoes depending on your rotation.
Harvesting potatoes is a satisfying job. Care must be taken not to stick the fork through them. So, insert your fork 30-40cm from the stalk and lever them up all around.
When harvesting maincrop potatoes for storage they must be sorted and the skins dried. Harvest all of them even the marbles as they will be weeds next year. Divide them into marbles and damaged potatoes for animals, small green potatoes that can be destroyed, slightly damaged potatoes for immediate use, seed for next year, and perfect potatoes, for storage.

Storage Potatoes need to be dry when stored and keep best in a cool environment, but will rot if frozen, so in ireland, unless you have a cold store, a cool shed or back kitchen is best. We keep them in the unheated back kitchen as it is rodent free. In cold weather potatoes must be covered by straw or other insulating material to protect from frost.
Selecting potatoes for seed.
You can save your own seed for potatoes if you are a bit careful. Potatoes suffer from viruses which reduce yield and are not immediately obvious in the field. Plants with viruses may be stunted, have curled or yellow leaves and generally look poorly. Always select potatoes for seed from best looking plants. Seed potatoes are traditionally produced in Donegal and in high altitude sites where the aphids that spread viruses are absent. The potatoes for seed should be approximately egg-sized, but larger green potatoes can be used for seed too. The seed potatoes should be left in the light for a few days to harden the skins, but not allowed to dry out too much. If seed potatoes are stored at too high a temperature they will be come wrinkled prunes and use up all their energy supplies before they are planted. This is especially true for early potatoes that are programmed to sprout early. If you have room for them in the bottom of the fridge that will help hold them. As soon as they start to sprout they must be kept in the light or the sprouts will look for light and grow too long. They will then fall off when you handle them. A couple of weeks before planting, seed potatoes should be put n a cool bright area for the sprouts to develop. This is called chitting.

There are still a few places on:

By the way, we don't sell seed potatoes.

1 comment:

  1. The Crazy Cat LadyMay 8, 2012 at 1:10 PM

    Saved your site as a guide to my first year as a veggy/fruit grower! Gr8 advice about growing potatoes. Now have in my potatoes, carrots, onions, turnips, leeks, peas, parsley, garlic, raspberries, strawberries, blueberries, gooseberries and rhubarb!! All advice gratefully accepted!!!!