How to grow potatoes. For me potatoes are the backbone of the vegetable garden. You get the seed potatoes in relatively early and apart from some earthing up and keeping an eye out for blight there is very little to do. They break up the soil nicely for the following crop and should provide an excellent yield from a relatively small space. There is also something so exciting about turning the soil at harvest time to see what you’ve got. I must admit to being a bit of a klutz here and manage to stab nearly every one with the prongs of my fork…. One thing I struggled to understand when I started growing was the different potato groups, first earlies, second earlies, I mean what’s all that about? Well it’s quite simple really and refers to the amount of time the potato takes to mature.
How long do potatoes take to grow?
- First earlies – 90 days. Plant mid march. Harvest late June/July Recommended Variety: Homeguard, Duke of York.
- Second earlies – 110 days. Plant early April. Harvest July Recommended Variety: Orla
- Maincrop – 135 days. Plant mid to late April. Harvest October onwards. Recommended Variety: Setanta.
- Late Maincrop – 160 days. Plant mid to late April. Harvest October onwards. Recommended Variety: Sarpo Mira
If you are a beginner I’d highly recommend you stick to earlies as they take up less space and will provide you with a quicker crop. There is also a noticeable difference in the flavour of freshly dug early potatoes as opposed to maincrop potatoes which you store. If you have a small plot, as most new gardeners do, you will have time to put in another crop after the potatoes and thus make better use of the space in your garden. Importantly you’re also likely to avoid the disease potato blight for the reasons I’ll explain now:
Potato Blight is an air borne disease which is at its worst in the more humid weather of July and August. Organically there is really no way to treat it and is highly likely to occur. There are 2 main ways the organic gardener can cope with the problem which is based more on avoiding rather than treating the disease.
- Stick to the early seed potato varieties as they will be ready to harvest before the worst of the blight hits. You may still get a small amount but this can be controlled by removing any diseased leaves or stems. Most of the growth will have taken place before this happens.
- Grow blight resistant varieties. We now have an excellent choice of blight resistant potato varieties. They are not completely immune to attack but will stay healthy for longer and won’t suffer as badly. If you have a serious blight problem you should remove the foliage down to 2in from the ground. This will stop the growth of the tubers but with a blight resistant strain you should have the majority of the growth done before this happens.
Chitting potatoes is leaving the seed potato exposed to light for a week or two causing it to produce sprouts. The idea is it gives you a head start of about 10 days before you plant them in the ground. A potato has a blunt end with a number of small depressions or ‘eyes’. Place the potatoes in egg boxes on a windowsill with the ‘eyes’ facing upwards for 5-6 weeks until they start to form small shoots. They are ready to plant when the shoots are about 1.5 to 2cm long. You don’t want the shoots to get too long or they are likely to snap off when you plant the potato. N.B. You don’t have to do this, they will still grow if you just stick them in the ground. It just speeds things up which is only relevant for early planted crops.
Planting seed potatoes in ridges is recommended as it makes them much easier to earth up. Ridges are rows of mounded soil, here’s a photo of our potato beds in the Quickcrop garden. Plant the potato 10 to 15cm deep into good fertile soil. It is traditional to plant with the side with most ‘eyes’ or little shoots facing up. In our experience this makes little or no difference.
Earlies: 25cm between plants, 50 cm between rows. Maincrop: 35cm between plants, 75cm between rows. You can have break now and watch our organic expert Klaus Laitenberger and myself bring you through the potato growing year:
Crop Care Earthing up
Earthing up means dragging the surrounding soil up around the growing shoots of the potato plant. It might feel odd to cover the new growth but it has a number of benefits:
- If you’ve planted early potatoes keep an eye out for frost as the early shoots can easily be damaged, earth up to protect.
- As potatoes grow they will push up though the soil and become exposed to light tuning them green. Green potatoes are poisonous (the potato and tomato are both members of the deadly nightshade family!) so obviously we ant to avoid this.
- A good amount of soil covering the potatoes make it less likely blight spores will wash down and effect the tubers.
- Weeds are kept down and it is also thought to increase the yield.
Apart from frost protection you should earth up when the plant is approx 20cm high.
You are unlikely to get blight before July so you should be o.k. with the early varieties. You will notice blight on the leaves first and if the attack isn’t too severe you can just remove the affected leaves. If the problem persists you will need to remove all the foliage as already mentioned. Don’t dig up the potatoes at this stage as the tubers need to form a skin for storage. You should leave maincrop varieties in the ground until October to allow this to happen.
Foliar and tuber blight resistance
Blight attacks the leaves of your potato plant first and, if left unchecked will travel down and infect your tubers. Blight resistance in potatoes can refer to the leaves (foliar) or the tuber (the potato under the ground) but most people tend to think of foliar resistance only. A potato with mid range foliar but high tuber resistance means the plant may be infected to such a degree above the ground that the foliage needs to be removed but the crop underground will be unaffected and should store perfectly well.
The British Potato Variety Database
The British potato variety database is a handy online site which gives you information on most varieties you’re likely to encounter as a home grower. It’s not the most fabulous looking site in the world but the information is excellent and gives foliar and tuber blight resistance and well as resistance to other pests and diseases like common scab or eelworm. A very handy tool when you’re deciding what varieties to grow.
Many books will tell you to wait till the plant flowers before harvesting potatoes but some varieties, like Orla, don’t flower at all in some years. See harvesting times above. Early potato varieties should be harvested as you need them because they don’t store well. There is nothing nicer than a freshly dug new potato, get ’em out of the ground and into the pot! Maincrop varieties can remain in the ground over winter unless you have a wet garden or a high slug population. I think it’s safer to dig and store, especially in Ireland. Store in boxes of sand or hessian potato bags in a cool frost free shed. Check periodically for any signs of rot and remove affected tubers. It’s important you harvest all the potatoes or they’ll come up again next year as weeds!