Self-Sufficient Veg: Potatoes 101
by AGRIC on MARCH 1, 2008 - 1 Comment in self-sufficiency
This way up, King Edward

The following info may look simplistic, but it is sound, experience-based , common-sense advice, and if you follow it, you will have success with potato-growing.

If you’re trying to be self-sufficient in cool temperate regions, potatoes will likely be your most important crop apart from wheat.

Even without special storage facilities you can just about eat potatoes all year round. They are a productive, easy to cultivate and usually reliable crop, and provide a good supply of carbohydrate, protein and vitamins for your diet. Apparently no other crop produces more energy per acre than potatoes. I wonder what people did before they arrived from South America in the 16th century?

You grow potatoes by planting a potato! A whole host of important things stem from that fact:

Most important is disease. If the potato you plant has a disease then the plants that grow from it will almost certainly have that disease. Very bad news for you and for anyone growing potatoes near you since aphids are very good at spreading disease between potatoes.

So, you would be very unwise to plant just any old potato, you need to do all you can to ensure ‘clean’ seed: buy certified seed potatoes (as sold by all reputable seed merchants). If you save your own seed potatoes you need to be very very very careful, never save seed potatoes from any plants that have shown disease or poor performance, plan to replace a third of your seed potatoes from fresh certified supplies every year – and replace all your seed potatoes if you think you’ve had problems. It’s probably unwise to save potatoes for seed if you grow on an allotment or community garden where other people are growing potatoes since yours could catch a virus from theirs.

It’s pretty stupid to plant potatoes bought from supermarkets and grocery shops – you’ve no idea what nasty diseases they may have. But I’ve done it 4 times for a very small number of spuds in the last 5 years, perhaps 1% of my seed potatoes in that time, I’ve been as careful as possible and it has not caused me an obvious serious problem yet, but it will if I persist in being stupid. Potato viruses and diseases are like HIV, you can’t tell by looking. Wear a condom and buy certified seed potatoes.

Nowadays seed potatoes are almost always produced from mini tubers, which are produced in close to laboratory conditions from virus free stock. These are grown on for 3 to 5 years by specialist seed potato growers in very strictly controlled conditions before you buy them from seed merchants. It’s amazing how much care is taken to produce clean seed potatoes, it’s not for the fun of it, it’s to minimise the risk of viruses and diseases decimating our potato crops. So, give respect and don’t mess things up for everyone else, OK.

When you buy potatoes to eat from your supermarket or grocery store you’ll probably have a choice of about 5 varieties at any time if you’re lucky; well, in UK you can buy about 150 different varieties of seed potatoes – and most of them taste noticably better than the ones you buy in shops. For most people a potato is just a potato, it was so for me until I started growing my own and happily learned better. Last year we grew 30 different varieties at Phoenix, this year it will be about 35.

Another funny thing about potatoes: the same variety can often taste quite different when grown in different places and soils, some will do well in one place and not in another even nearby, and the weather – especially moisture and temperature – can have surprisingly different effects on different varieties’ yields. You need to experiment with different varieties on your land to discover what works best for you.

Potatoes have a ‘this way up’ – you need to know how to spot it but that’s not hard. Up is the ‘rose’ end, and that’s where most of the ‘eyes’ are, often there is a faint half moon shaped ridge beneath each eye to help you and a belly button on the down end where it attached to the parent plant. Varieties can be quite different, some are easy to spot ‘up’, some are more challenging.

One planted potato does not equal one plant! Every shoot that grows from the seed potato is a plant. That has implications, think about what those might be before reading on (it’s good for you: a thinking gardener is a better gardener!).

When you plant a potato you are planting a clump of plants together, if you recollect what I said before about spacing – equidistant spacing between plants being optimal – you’ll realise that is not good. Closely spaced plants result in more but smaller produce compared with widely spaced plants, and you generally don’t want a crop of many very small potatoes. An additional disadvantage with overcrowded potatoes is a good crop can force tubers to the surface and cause them to ‘green’.

You can manage this to improve the situation. First you can use seed potatoes that have not too many eyes so you don’t get too many plants clumped together. Seed potatoes about the size of a hen’s egg or a little smaller are about best for most varieties. If your potato has more sprouts than you want then you can rub the surplus sprouts out when you plant.

You can cut your seed potatoes into portions with about the right number of eyes. I really don’t like this and have never done it – cut potatoes can easily rot and provide a site for disease to attack. If you do then you should use something to dry the cut surface (sawdust, flour, or talc would work) and let it dry for a day, preferably in bright sunlight if you have it, before planting.

Your objective is to grow 2 to 3 ‘plants’ per square foot (20 to 30 per square metre), this seems to be about optimal for good crops of decent sized potatoes.

An advantage us manual gardeners have over the mechanised producers is the care we can take when planting. This is particularly so with potatoes – it means we can ‘chit’ them to get a head start. Chitting is just putting seed potatoes rose end up in a light and cool place for about 4 weeks before planting so that they produce strong, green shoots. The ideal temperature is 50 F (10 C), if warmer then they will sprout faster so you should reduce the chitting time. Egg boxes are excellent for chitting potatoes.

Frost kills any above ground potato foliage and will set your potatoes back a week or more if afflicted. In UK this is the prime determinent of when potatoes are planted – you aim to have your potatoes poking through the soil’s surface the day after your last frost. This is, of course, impossible unless you are very lucky or a time traveller.

If you are planting nicely sprouted seed potatoes (sprouts about 1″ to 1.5″ long, 3 to 4 cm) in cold ground about 5″ (12cm) deep then it will take between 3 and 6 weeks for the sprouts to emerge above ground – dependent on soil temperatures and potato variety. So if your last frost is probably 15th May you should plant about 15th April. You should start chitting about 4 weeks prior to that at 50 F (10 C), about mid March.

But in UK the last frosts are very variable. In 2007 the last frost at Phoenix, Culbokie was 2nd April I think, yet the probable date for last frost there is about 20th May! You need a strategy that works for most possibilities.

First keep your potatoes cool and listen to them. At temperatures above 40 F (5 C) they will be inclined to sprout but some sprout noticably sooner than others. As soon as they start sprouting you need to put them somewhere light and cool to chit and begin to plan your planting accordingly. If they are too far ahead of what you can do regarding planting then put them in your fridge if you can to slow them down.

Think of planting the earliest varieties under cloche or fleece, even aim to do this, you can be eating early potatoes a month sooner this way.

Spread your planting dates over several weeks if you are taking a risk on frost. That way all your crop won’t be afflicted if a frost hits when some have emerged. Be ready and able to mulch them with straw, bracken, grass, fleece or similar if a surprise late frost threatens. It’s mostly not the frost that kills but the rapid thawing of plant tissues – usually due to bright sun which often comes straight after frost – you can save the day by covering frosted potatoes or by spraying with cold water before the sun hits them.

Two more posts on potatoes coming soon I think. One about varieties, links and buying, another about growing.

Check out this blog on potato growing – its one of the best.

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1 comment

1 Kat { 03.29.13 at 4:02 am }

Brilliantly informative, thank you! Do you have advice for those of us, with not much ground space, who have to grow spuds in sacks?

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