Growing potatoes in a bin bag

There’s no doubt that growing potatoes in the open ground, whether a garden bed or an allotment, takes up a lot of space. And a lot of space is usually something the urban gardener often doesn’t have. 

However, you don’t have to grow them in the open ground at all. You can grow potatoes in a container, ideally a strong sack … or indeed, a bin liner. And right now in March is a good time to start them off.

You might have seen advertisements in the Sunday magazines for special potato sacks, but you don’t need them. A nice strong black binbag will do. Or a compost bag, so long as it has that black lining inside. The black lining is to keep the light out, so that the potatoes inside don’t go green.

Growing in a container

The best type of potatoes for planting in a container are early varieties - those which reach maturity the quickest and are ready for harvesting around 110 days after planting. We successfully raised Lady Christl, Anya and Charlotte potatoes grown in bin bags at the Secret Garden Club. 

Lady Christl potatoes have beautiful, unblemished yellow skins and creamy white flesh. The potato is firm with a delicate buttery flavour and they make a delicious salad. The Anya variety, originally grown for Sainsburys, is a cross between Desiree and Pink Fir Apple, the Desiree side of the family smoothing out the knobbles and bumps that are characteristic of Pink Fir Apples, leaving Anya relatively smoother skinned and nutty flavoured. Charlottes are a classic salad potato with a waxy texture.

Freshly dug Lady Christl potatoes.

When you buy your seed potatoes, it's a good idea to let them develop little shoots, called 'chits', before you plant them in your bin bag. The potatoes will chit, ie, send out these little shoots, if they are kept in a light cool place. Note, a light cool place. If you want to store potatoes for eating, keep them in the dark. If you want to store them before planting, keep them in the light.

It’s not essential to chit potatoes but it does get them off to a good head start in the ground. It also helps you to plant them the right way up - the shoots should be pointing up towards the sky.

Each compost bag will take three seed potatoes, seed potatoes being the starter spuds which will grow into new potato plants. From each seed potato you should be able to harvest around eight or nine eating potatoes.

While growing potatoes in a container obviously takes up less space than raising them in the open ground, there are other advantages as well:

• It's less hard work – no digging;
• Portability 1 – if you get a bad weather warning (eg, frost) when the plants are young and tender, you can move them indoors/under cover;
• Portability 2 – you can place the bags more or less wherever you like.
• There is less risk of disease – your purpose-bought compost shouldn’t be harbouring blight spores, eelworms or any other nasties;
• You don’t need to dig out the potatoes with a fork or spade, so there is little or no chance of damaging the spuds when harvesting;
• Gardeners often miss very small potatoes and leave them in the ground over the autumn and winter. By growing them in a bag you can ensure you harvest your entire crop.

How to plant potatoes in a bag

1) The first thing to do is to put about three inches of compost in the bottom of the bag, spread evenly. Make it easier for yourself by rolling the sides of the bag down so that your bag is about six inches tall. You’ll want the sides rolled down anyway after you plant the potatoes – if you keep the bags at full height your potatoes will never see the sun and they won’t grow.

2) Next you want to take a sharpened pencil or sharp stick and make some drainage holes in the bottom of your potato bag. This is very important – you do not want waterlogged potatoes.  They will rot, and rotten potatoes stink.

So, make about 5-6 drainage holes at the foot of each bag.

3) Now place three potatoes into the bag. Space them out evenly.

Always use seed potatoes, ie, bought from a nursery or garden centre specifically for growing. Seed potatoes should be guaranteed free from viruses, which culinary potatoes won’t be. Potatoes in the shops may have been sprayed with a shoot suppressant.

Potatoes in the shops may not have been grown in the UK and so may not be well adapted to grow here. Many, if not most, of the seed potatoes grown in the UK come from Scotland and are bred to grow well in our conditions.

4) The potatoes should go into the sack with the chits uppermost.

Yup, see them little roots...they go upwards, those will be the shoots growing above the ground to grab some sunlight for the plant.

You can grow potatoes without chitting them first but they take longer to get going. You can also cut seed potatoes up into divisions each with its own little chit and plant them individually, but you do get bigger plants and more potatoes by planting the whole spud, chits and all.

5) Once the potatoes are in, cover them with more compost: aim to have a layer of compost about 2-3 inches thick over the chits.

6) Finally, water them lightly. They don’t need to be soaked. Check that water is seeping out of the drainage holes.

7) Put the potato bag outside somewhere light and somewhere reasonably sheltered.

You’ll need to bring the bag inside if a frost is forecast. We may have had a very mild winter this year but we could easily still get a cold snap in March in London; much more unusual in April, although we’ve had late frosts in each of the last two years.

8) After about 2-3 weeks you’ll see the dark green leaves poking up through the soil surface. Once the leaves are about 3-4 inches above the surface of the compost, add more compost to the bag, until the green tops are only just visible above the soil surface.

You’ll probably need to starting unroll the sides to accommodate the new compost as well. This is an ongoing process. Every time the plant grows so that you have about 3-4 inches of stem and leaves above the surface, unroll the sides a little more and add more compost.

If it rains a couple of times a week, you probably won’t need to water them. But do check your compost: if it’s very dry, then water it. Make sure any excess water is running out through those drainage holes. If it rains a lot and you put your hand in and the compost is sodden, move the bag under cover for a few days to let it dry out a bit.

The potatoes will take about three and a half months to reach maturity and edible develop tubers.

So, in about mid-June, you can put on a pair of gloves and stick your hand into the compost. If the lumps are still tiny, leave them longer. If you can feel that you have big potatoes, start harvesting.

Other signs are also useful: once the potato plant is flowering you can try digging up some spuds, or your deep green foliage might start turning yellowy and begin to wilt.

The best way to harvest here is simply to up-end the bag on to a surface and pick out the potatoes. Put the rest of the plant on the compost heap and spread the compost on your garden beds.

Charlotte potatoes spilling over the top of their bin bags.