Growing potatoes

Potatoes are one of the staples of our diet. They also grow well in the acidic soil and the cool, damp climate of north-eastern Scotland.

However, potatoes are not necessarily one of the best vegetables to grow, particularly if space is limited.

Potatoes are relatively cheap to buy in large quantities for the table, they need a lot of space, and there’s a lot of work involved if the yield is to be maximised. When we lived in the city and had a small vegetable garden, we didn’t grow potatoes as it made more sense to use the limited space to grow vegetables that were more expensive to buy in the shops.

On the croft, it makes sense to grow potatoes as cultivation levels ground churned up by pigs, we have enough space to grow them without impinging on other crops, and we can grow enough not just for our needs to provide a useful supplement for feeding pigs in winter.

We grow the more popular potato varieties on a field scale to provide the bulk of our needs, but we also grow less common and heritage varieties in our vegetable beds.

Potatoes prefer open, sunny ground. When we grow potatoes in the boar pen shadowed by our sitka spruce wind break, the haulms (the leafy tops) tend to be long, weak and easy damaged by wind. Yields are less, too.

Before planting potatoes in the vegetable beds, we prepare the soil during autumn or winter by digging in large amounts of well-rotted pig and chicken manure. A 4m by 2m bed takes around four large barrow-loads of muck.

We use a different approach when planting potatoes in the fields as they often go in after the pigs, which can mean the ground can’t be dug in autumn or winter. Instead, we plough or rotary hoe the field to be planted in early spring, when the ground is sufficiently dry. The ground is then ridged and well-rotted muck is manually spread along the furrows. (If we had a muck spreader, we could spread the muck before ploughing.)

Two-thirds of our crop is grown from seed potatoes selected from the previous year’s harvest and one-third from commercial seed potatoes bought in late January. The aim is to prevent disease build-up. We replace entire varieties, never mixing saved seed potatoes with new. (In some cases, it is illegal to save seed potatoes as the varieties are subject to plant breeder’s rights.)

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In preparation for planting the early varieties, we lay the seed potatoes out in large trays in late January with the eyes uppermost. The trays are usually placed in the spare bedroom with the window blanked off and the radiator turned down to keep the room temperature around 10ºC. We can’t put them in our outbuildings as the temperatures can be well below freezing March, or even April.

In late February, the window is partially uncovered to allow some light in and encourage the potatoes to develop sturdy shoots. By sprouting the earlies, we get a longer growing season, an earlier crop and a heavier yield.

We don’t intentionally sprout the main crop varieties as there’s not enough room in the spare bedroom for them. Instead, they’re kept in steel coal bins, heavily insulated with straw. We lose some of the outside potatoes to frost in the hardest winters but never more than five to 10 per cent.

The first earlies are planted first, usually around mid-April. We ridge and furrow the beds with two-foot spacings between the centre of each furrow, then place the seed potatoes along the bottom of the furrow with their shoots upwards. Earlies are planted at wellie boot spacing, ie about 12 inches apart.

The ridges are pulled over the furrows, producing new ridges 4-6 inches deep over the potatoes with furrows alongside. This usually provides enough protection from late frosts in late April and May, although it is sometimes necessary to earth up or place a layer of straw over the ridges if shoots emerge before the frosts have ended.

Second earlies are planted in the same manner, about a fortnight after the first earlies.

When the first earlies are going in, it’s usually warm enough in our outbuildings for the maincrop varieties to avoid frost damage. If this is the case, we clear the pens in our byres and spread the maincrop seed potatoes over the floor. As the maincrop varieties go in about four weeks after the first earlies, this is usually enough to see them develop small shoots although they’re not as heavily sprouted as the seed potatoes started in the house.

To plant the main crop, we manually spread well-rotted muck along the furrows and lay the seed potatoes on top. Spacing is at double wellie-boot intervals, ie 24 inches. Again, the ridges are turned onto the potatoes in their furrows, creating new furrows alongside.

As we don’t use herbicides, we’ve found it vital to weed the potatoes at least weekly. Chickweed in particular is prone to swamping the potato haulms, depriving them of light and creating the damp conditions in which potato blight thrives. The fastest manual method is with a long-handled agricultural hoe, also known as an azada.

The potatoes are earthed up when they reach about nine inches in height, and at fortnightly intervals thereafter until the leaves meet between the ridges. We’ve never yet needed to water our potatoes but in drier areas frequent watering is advisable, especially during the first eight to 10 weeks.

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The main causes of crop damage that we’ve encountered are hard frosts and late blight. Slugs are a much lesser problem, especially now that we use nematodes to control them.

We’ve not experienced problems with blackleg or aphis-spread viruses, although the potato inspector who lives across from our croft tells us they can be a problem on the commercial farms.

To combat late blight, we plant a number of blight-resistant varieties. However, not all of these grow as well in our conditions as less resistant heritage varieties. Others lack the flavour and texture of heritage varieties.

We also strive to maintain good air flow along the rows to keep the foliage relatively dry (weed, weed and weed some more). If the weather is warm and damp, we spray with Bordeaux mixture at fortnightly intervals, usually from June onwards and no more than three times in a season.

Using Bordeaux mixture is frowned on in some quarters, but we rely on a good crop of potatoes to feed us for nine months and supplement the pig rations for three. Simply accepting large losses is not an option, so we spray if necessary.

Besides, if we didn’t spray and allowed the crop to fail, we’d have to buy potatoes from the shops, shops buy them from commercial farms, and that means they will be sprayed with either Bordeaux mixture or Dithane. Even organic potato crops are sprayed with Bordeaux mixture.

Potato harvesting is entirely dependent on the weather. With a warm spring and good rain early on, we can harvest first earlies around the end of June, although mid-July is more common. When we’ve had a particularly cold spring, the harvest is delayed until late July or even early August.

We start harvesting second earlies about a month after starting to lift the first earlies. Both early crops are lifted as needed, forking up several plants at a time and only cutting the remaining plants’ haulms back only if blight is likely.

When we lift potatoes with a fork, we push the tines of a garden fork deep into the centre of the furrow, angling it under the adjoining ridge, and levering the plant up before flipping it upside down into the next furrow. We used to push the fork into the base of the ridge but found we were skewering many potatoes.

A potato fork, with wider tines set closer together and rounded points, would be faster and easier with less risk of skewering potatoes, but we haven’t been able to justify the cost of a one or two as yet.

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Main crop potatoes take at least five months to reach maturity and sometimes longer as our summer temperatures are rarely conducive to optimal growth rate. In other words, we have few days where the temperature is higher than 20ºC. On the plus side, the cool conditions allow slower development and prolong leaf cover, which allows the plants to make the most of what sunshine there is.

If we have blight on a few plants, we cut the haulms from those and burn them while continuing to spray with Bordeax mixture. If blight is present on more than 10-15 per cent of the main crop plants, we cut all the haulms off and burn them. The tubers are left in the ground to mature, which gives them thicker skins that are more able to withstand long storage.

When we’re fortunate enough to escape blight, we cut the haulms back about a fortnight before harvesting and again leave the tubers in the ground to mature. We use a scythe to cut the haulms, which are left to dry and then burned.

To test whether the potatoes are mature or not, we lift a couple of tubers and rub the skin with a thumb. If the skin comes off, the potatoes aren’t mature. If the skin stays in place, the potatoes are ready for storage.

We aim to lift the main crop varieties during the mid-October school holidays, which are known locally as the Tattie Holidays. Lifting the crop during the holidays means Linda and the boys are all available to help with the job.

One of our neighbours loans us his 1950s tattie spinner, which is hitched to either his tractor or that of another neighbour and we lift potatoes in the old way: the tractor-towed spinner slices through the soil below the potatoes, a series of rotating arms flings them into a screen, they drop the ground and a line of willing helpers collects them in baskets.

The baskets are emptied into hessian sacks dotted at intervals across the field. It’s a laborious job, but it’s fun, sociable and beats lifting an entire field of tatties with forks.

When the entire crop is lifted, the hessian sacks are loaded onto our Land Rover Defender pick-up to be transported down to the steading for cleaning and sorted.

If the soil is reasonably dry, the potatoes can be spread on the hard standing for few hours before being swept clean with old brooms. If the soil is wet and clinging to the potatoes, we gently hose and brush them before leaving them to dry.

When dry, the potatoes are sorted. The best, hen’s egg-sized tubers are kept for seed for the following year, unless they’re due to be replaced with new stock. Broken potatoes are put aside for immediate use, either by us or for the pigs. Diseased and green potatoes are put aside to be burned.

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We store the potatoes in 10-hundredweight steel coal bunkers as these are rat-proof as well as keeping out the light. The bunkers’ lids and bases have 10mm holes drilled in them for ventilation. They’re spaced 12 inches apart and sat on pallets to maintain air flow.

Before using the bunkers, we thoroughly wash and disinfect them. Once they’re dry, we place about six inches of straw on the base to insulate the potatoes from freezing temperatures.

Alternating layers of potatoes and straw are placed on the initial layer of straw, with 4-6 inches of straw between the potatoes and the sides of the bunkers. The final layer of potatoes is covered with a six-inch layer of straw.

Depending on the weather, we’ve found potatoes will keep in the bunker until at least the end of April and, in cooler weather, until the end of May. Seed potatoes are kept separate to the eating potatoes. All are checked regularly and any that rot or freeze are discarded.

We have considered using clamps to store potatoes, which involves digging a shallow trench, lining it with straw, placing the potatoes on top, covering them with more straw and placing the soil back over the top.

However, neighbouring farmers who used this approach in the past said they inevitably lost large numbers to rats, freezing and rot. To overcome the losses, it was necessary to grow and store many more potatoes than were needed.

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The varieties we’ve grown include:

Potatoes and their uses, pt 1: Milva, Cara, Verity and Pentland Dell (all maincrop).

Potatoes and their uses (part 2): Pink Fir Apple (salad); Colleen and Duke of York (first early); Maris Peer, Edzell Blue and Catriona (second earlies); Lady Balfour (early main-crop); and Remarka, Valor, Golden Wonder and Picasso (all main-crop). We’ve also tried growing Champion (maincrop) from micro-plants.

Potato varieties—Red Duke of York (first early)

Potato varieties—Catriona (second early)

Potato varieties—Courage (second early)

Potato varieties—Valor (maincrop)

11 Responses to “Growing potatoes”

  1. Another in my occasional series of posts detailing how we grow vegetables in the poor, acid soils and cool, damp climate of north-eastern Scotland.

  2. Very nice and informative post! Interesting to see your storage using the straw to isolate and to keep layers separate.

    One slight misconception that I can’t refrain from pointing out (I know, I am a pedant sometimes ;) ) is with regards to the following sentence:

    >The aim is to prevent disease build-up and hybridisation of varieties.

    Unless you grow potatoes from the tomato-like fruit there’s no risk of hybridisation of the tubers, they are basically all clones of the parent.

    • Sorry, I finished this very late at night and was in autopilot mode by then. Whenever I write something about seed saving I automatically put in something about considering the possibility of hybridisation. When my brain is awake I know potato tubers are not seed, but after a long day it’s not always possible to maintain that degree of cerebral activity.

      • We all have these moments of falling back to automatisms when tired ;)

        I was wondering whether I should comment and how to comment. Considering it is a very useful and informative post, I figured it was worth pointing it out — the more people willing to grow some of their own potatoes the better :)

        Here in town, with rather limited garden space, we grow a single bed or two of early potatoes which we harvest small. Buying these small, but delicious, early potatoes is rather expensive — for these we consider it worth our precious gardening space.

  3. Teresa Silverthorn Reply 25 January, 2012 at 12:33

    Excellent article, nonetheless. Tubers, seeds…no matter.

    Your blog could easily be reformatted into a wonderful book.

    Fascinating read, and resourceful, as well. It reminds me of an old series of books called “Foxfire” in the 1970′s. It was quite popular.

    Yours could be the “Foxfire” of the new millennium.

  4. Too long! Blog posts should be 500 words. At most! Cut it down. Peeps don’t have time for wordy stuff any more. Why’s twitter so popular? Shortness. And why grow potatoes when you can buy them in the shops? You English are crazy.

    • Speak for yourself Kyle. I certainly have the time, inclination and education to read long posts and twitter is not popular in my house.

      Oh and for your information Stonehead is not English, he is Australian and I think his wife is Scottish.

      And where in the world do you live?

  5. Teresa Silverthorn Reply 25 January, 2012 at 18:21

    Comments like Kyle’s should be shorter.

    Maybe one word.
    ;)

  6. Thank you Stoney. I shall certainly use this to decide which variety to grow this year. And as far as I’m concerned another reason to grow your own potatoes is for the taste, to me they taste so much better.

    • I’m glad the post was of some use. Taste is often down to the variety—many of the modern varieties might be more resistance to disease but they’re taste can be overly mild. I appreciate that this is often seen as desirable in a commercial product—bland doesn’t put people off in the way strong flavours can—but I usually prefer to taste the potatoes. There are some dishes where I want the potato flavour to be in the background, but by and large I want to know I’m eating a potato.

  7. Really informative post! … and to think I was proud when I got my nan and grandad to grow potatoes for the first time in their field :D Obviously not on the same scale, but it still worked!

    Keep up the good work :)

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