Growing and harvesting potatoes
One of the easiest and most satisfying vegetables to grow at home has to be potatoes. Once you get to know some of the potato specific terms, growing potatoes is pretty straight forward. I guarantee, when you harvest your first homegrown potatoes, you’ll love the magic of those beautiful tubers emerging form the soil. And, of course, homegrown potatoes taste amazing!
Here’s all you need to know about growing potatoes:
What is the difference between earlies and maincrop potatoes?
This is often confusing for first time potato growers but it’s quite straightforward, it’s just a way of harvesting your different tubers over a long season. First earlies are like the new potatoes you buy in the shops. You plant them earliest in the year and then harvest them first. Really it’s just a way of getting your hands on some delicious potatoes without having to wait all summer.
After your first earlies come your second earlies. These are still new potatoes, but you plant them a little later and harvest them a little later too.
Finally, you plant your maincrop potatoes. You plant these later and harvest them much later in the summer and into autumn. These are bigger potatoes and, because they’re more mature, they can be stored. They will also be a bigger crop per plant. You can also plant a last sneaky crop in late summer, which you can harvest near Christmas.
Preparing for the growing season
If you’ve planned far enough in advance, it’s best to prepare your ground in the late autumn, but if you’ve missed the boat, it’s fine to do it just before planting. If you’re going to use containers you don’t have to be quite so organised. Make sure your patch is free from weeds and add some manure or compost to help feed your new plants. Potatoes need a sunny site to get a good crop.
Seed potatoes, what are they? and where to get them.
Make sure you’ve ordered your seed potatoes in plenty of time before you plan to plant them. Buying seed potatoes rather than using eating potatoes ensures that they are virus free. It also means you can choose more interesting varieties than the usual standard supermarket selection. You can usually get seed potatoes at your local garden centre, but online stores might have a wider selection.
Varieties of potato
Seed potatoes will be labelled as first earlies, second earlies or maincrop. Last year I grew ‘Rocket’ as my early crop. They were a lovely new potato, really waxy and tasty with perfect looking tubers. Another good variety is ‘Arran pilot’. It’s very disease resistant and even slug resistant.
For second earlies, you can’t go too far wrong with ‘Charlotte’. It’s a really popular choice and although it’s a new potato, it roasts well too. Another popular variety is ‘Nicola’.
For the maincrop, it’s fun to grow a couple of different varieties if you have the space. I love ‘Pink Fir Apple’, a very knobbly, unusual looking potato with excellent flavour. There’s the ever-popular ‘Maris Piper’, which has to be the best for chips.
The best one for blight resistance (more about that later), is ‘Sarpo Miro’. It’s also a very pretty pink colour, but for a really funky looking one, ‘Apache’ is purple and yellow, quite a surprise when you dig that one up!
It’s another one of those weird potato growing words. It just means getting the seed potatoes to start sprouting before you plant them. You know when you’ve forgotten to eat a couple of spuds you’ve left in a bag and you find them growing stuff? It’s just that.
You should do this in January or February. An old egg tray is perfect. Put the seed potatoes in with the eyes pointing upwards and keep in a dry, light place until they’ve grown a couple of centimetres of shoots, then they’re ready for planting. Some vegetable gardeners don’t think this is necessary so don’t worry if you forget to do this bit, but I think it’s good to give them a head start.
You only need 3 or 4 shoots on each potato, so if they’ve grown more, either rub the extra ones off, or you can actually slice the potato, leaving some shoots on each chunk and you magically get extra ones to plant. If you do this, let the chunks dry out for a couple of days before planting, or they might rot.
When to sow potatoes.
Now we’ve established how to get a long season of potato harvests, you need to know when to plant them. This can vary a bit depending on where you are in the country and what’s going on with the weather that year. The RHS (Royal Horticultural Society) recommends planting:
- First earlies in late March
- Second earlies in early to mid-April
- Maincrop in mid to late April
This is in the UK. Have a look at what the weather is doing in your area. The potato plants can tolerate a light frost but not hard frosts. If frost is expected, wait a bit longer, they’ll soon catch up as the weather warms up. Ideally, the soil temperature should have reached about 10 degrees Celsius before sowing.
Growing potatoes in containers
If you’re short on space, potatoes grow really well in containers. You can get a really good crop in a small amount of space this way. You don’t need to do any digging, and when you’re ready to harvest, you just tip the whole container over and pick up your fabulous crop.
Suitable containers can be:
- A big plant pot
- Potato bags
- An old bin
- Raised bed
- Any container that’s big enough and you can put drainage holes in. (particularly important!)
With a plant pot, just make sure it’s big enough. At least a ten litre pot for one potato plant. That’s about the size a decent sized shrub would come in from a garden centre.
Potato bags are a great choice. They’re made for the purpose so they’re ideal. They should last a few seasons too, so they’re cost effective. They don’t take up much room, so you can use them in a small garden or even a balcony.
An old bin works well, but just make sure it’s not too big or the tall sides can end up shading the potato plants.
Last year I had a whole bunch of garden trugs that had broken handles. I put holes in the bottom, and they did really well as potato containers.
Whatever kind of container you use, you will need enough good quality compost or manure to fill it. Unless you’re super-keen and you make your own compost, (well done if you do!), this can become quite expensive, so bear that in mind when selecting your container. I used a 55 litre pot for potatoes last year, which took two whole bags of compost to fill making it a rather expensive harvest of potatoes.
When planting your seed potatoes in containers, don’t fill the pot up with compost straight away. Fill it about a quarter full, plant your seed potatoes on top, then cover with a few centimetres of compost.
As the leaves appear cover them again with compost. Keep doing this until you reach within a few centimetres of the top of the pot. It seems mad, but this encourages the plant to make a bigger crop of potatoes and stops any tubers near the surface from going green. More about that later.
Containers will dry out more quickly than the ground, so make sure you keep up with watering.
Sowing potatoes in the ground
This is generally a cheaper option than growing in containers as you don’t have to buy as much compost and you don’t have to buy the container. Growing potatoes in the ground in your garden does need space though. This is how much space you’ll need for each crop:
- First earlies- plant each seed potato 30cm apart with 60cm between rows.
- Second earlies- 37 cm apart, 75 cm between rows.
- Maincrop- 45 cm apart, 75 cm between rows.
- Sneaky late maincrop- 30 cm apart, 60 cm between rows.
Don’t be tempted to squash more in as you’ll just get a smaller crop per plant and potentially smaller potatoes. Less is definitely more in the world of potatoes.
If you prepared your potato bed in the autumn, you might need to give it a little dig over with a garden fork before you plant your seed potatoes, just to loosen any compacted soil. You can dig in some manure or compost at this point too. Then make a trench about 10-12 cm deep. You can use a spade or a hand trowel for this depending on how heavy your soil is.
Place each seed potato in the trench, the required distance apart, with the sprouts or eyes pointing upwards. Cover with soil. Don’t forget to label your rows. I like to put the date as well as the variety in case I need help deciding when to harvest.
If the tubers develop too near the surface, the sunlight can make them turn green. This also makes the potato poisonous. This is where earthing up comes in. When the leaves start to emerge from the soil you cover them with soil in a mound. It’s usually easier to go all the way along the rows and make a ridge. You can do this with a hoe if you have a large potato patch, or a hand trowel if you don’t have many plants. Continue doing this when more leaves emerge until your ridges are up to about 30 cm high.
You can also earth up with straw or compost, it has the same result. Straw has the added benefit of acting as a mulch which will keep the moisture in the soil. After harvesting you can just dig it into the soil where it will rot down.
Potatoes only need a few centimetres of water per week. It’s best to give them a good soak once a week rather than a little every day. This ensures that the water gets down to the roots.
If you’re not sure if you’ve watered enough, after you’ve finished watering, wait a few minutes, and then dig down into the soil with a hand trowel. You’ll be able to see how far the water has soaked through. You might be surprised how much water it takes to soak through deep enough.
A feed with an organic fertilizer every few weeks will make sure your potatoes develop well. A seaweed fertilizer is also a good idea as it adds minerals.
Pests and Diseases
The main disease that affects potatoes is blight. This is a fungus that loves a warm, wet summer. If you get it, there’s not much you can do, and it will destroy a crop of potatoes. Many seed potatoes have been bred to be blight resistant now, so particularly if you live in a wet area, it’s worth checking that your chosen variety is blight resistant.
Another common disease is Scab. This isn’t as serious as you can still eat the potatoes. They don’t look very nice though, as the name suggests, the tubers are covered in scabs. Once you peel them, the inside is usually fine. Scab is a bacterial infection which tends to happen more on light soils, particularly if it leans towards alkaline. Adding plenty of organic matter and making sure the plants don’t dry out in the first few weeks will help. As with blight, check your selected variety of seed potato to make sure it’s disease resistant.
Don’t sow potatoes in the same patch as the previous year as diseases might still be in the soil.
Potato rot happens after harvesting. To avoid this, don’t harvest when the ground is wet, and dry out the potatoes before storing.
As with most vegetables, slugs can be a problem with potatoes. Encouraging beneficial wildlife such as frogs, toads and hedgehogs to your plot will help control slugs. Don’t use pellets as these poison birds and other wildlife.
Harvesting potatoes, how to tell when they’re ready.
Weather plays a part in when potatoes are ready to harvest, but they should be ready:
- First earlies- 10-12 weeks after sowing, which should be June/ July
- Second earlies- 10-12 weeks, ready July/ August
- Maincrop- 15-20 weeks, late August- October
- Late maincrop- 11-12 weeks, ready November/December
For First and Second earlies, if they have developed flowers, wait until the flowers fade. If they only have flower buds, wait until they drop before harvesting. If you’re not sure, you can have an experimental dig and see if the tubers feel mature enough. Use a hand trowel or just your hand and feel under the plant. If the tubers are about egg-sized, they’re ready.
For the maincrop, wait until the foliage turns yellow, cut it off and wait for ten days. This gives the skins time to harden which is vital if you want to store them. Don’t worry if the foliage dies back by itself just leave for ten days after it’s died back.
The potato plants will usually have flowered by the time they’re ready to harvest. It’s more important to look at the foliage than the flowers though. If you do an experimental dig and find the tubers are ready before the plant has flowered, just go ahead and harvest them anyway.
As with the earlies, you can do an experimental dig and see how big the tubers are. If they’re big enough, it’s time to harvest them.
How to dig up potatoes
Do this on a dry day to avoid causing potato rot.
Use a garden fork rather than a spade to dig up your potatoes. If you hit one you will cause less damage with a fork, and it also loosens the soil rather than digging up a big clump.
Dig the fork in a few centimetres away from the side of a potato plant and lift up. You should be able to see some potatoes. I tend to feel with my hands after that to avoid damaging any tubers. You should feel them quite easily. If you find a very wet, squashy one, that’s what’s left of the seed potato.
When you think you’ve found them all, you can gently go back through the rows with the fork in case you’ve missed any.
How long can potatoes be left in the ground after they’re ready?
You can leave the potatoes in the ground after cutting off the foliage for up to two weeks if you don’t want to harvest them all at once. Or you can eat them straight away.
Don’t try to store earlies, just eat them as soon as possible, they don’t store well. You can leave them in the ground for up to two weeks after they’re ready though.
With the maincrop, let them dry out for a couple of days, don’t wash them. Put them in a paper or hessian sack, not plastic and not air-tight. Store them somewhere dark, cool, and well ventilated but not too dry. Somewhere like a cellar or loft can be a good option. Don’t store near apples as they’ll rot. Don’t keep any damaged or soft ones as the rot can spread to other potatoes.
Check the stored ones regularly and removed any bad looking ones. Hopefully, you’ll still be eating your harvest right into the winter!