Potato Growing Bags for Small Garden Spaces

Why Potatoes in Bags Make Sense

If you garden on a balcony, in a courtyard or on a narrow patch of paving behind the kitchen, potatoes can feel like something other people grow. They need depth, they need space, and the traditional allotment row seems designed for anyone but you. Growing bags change that entirely. A good potato bag holds around 40 to 50 litres of compost, stands roughly 45cm tall and takes up no more floor space than a bucket. You can move it to chase the sun, tuck it against a warm wall, or roll it under cover when frost threatens in May.

There are other advantages too. Because you control the compost and never plant into tired ground, you sidestep most soil-borne problems. Slugs find it harder to reach your tubers. And the whole crop comes out of a bag you can tip over in a single satisfying moment rather than digging a fork through the border. For first early varieties, a bag on a sunny patio will often outperform a row in heavy clay.

Choosing Your Bag and Your Seed Potatoes

Purpose-made potato bags are usually made from woven plastic or heavy felt with handles and drainage holes near the base. Felt breathes well and holds moisture steadily, while woven bags drain faster and suit wetter western climates. If you are improvising, a strong compost sack with plenty of holes punched in the bottom works fine, as does a builder's bucket with drainage drilled in.

Variety choice matters more than most people expect. In a bag you want potatoes that crop early and stay compact:

• First earlies such as 'Rocket', 'Casablanca' or 'Sharpe's Express' give you small, waxy new potatoes in roughly ten to twelve weeks from planting.
• Second earlies like 'Charlotte' or 'Kestrel' take a fortnight longer but yield more per bag and store better.
• Salad blues such as 'Blue Danube' are slower but look wonderful on the plate — worth one bag for the novelty alone.

Buy certified seed potatoes rather than using supermarket ones, which may carry disease and are often treated to suppress sprouting. Aim for three to five tubers per bag. Chit them from late January or February by standing them upright in an egg box or tray, rose end upwards, in a cool, bright, frost-free spot. Short, sturdy green shoots are what you want, not long pale ones stretching for the light.

Planting in Layers

Timing depends on where you are. In mild coastal and southern areas you can start bags under cover in March. Elsewhere, wait until April, or plant in mid-March and be ready to fleece or move the bag indoors when a late frost is forecast. The soil temperature wants to be around 7°C before the tubers go in.

Fill the bag to about a third with a loose, moisture-retentive mix — roughly half multipurpose compost and half soil-based compost, with a handful of slow-release potato fertiliser stirred through. Sit the chitted tubers on top, shoots uppermost, spacing them evenly and keeping them clear of the sides. Cover with 10 to 15cm of compost and water gently until it settles.

This layered approach is the heart of the method. Rather than burying tubers deeply at the start, you add compost as the shoots grow, and each buried stem produces more tubers. Keep the bag somewhere bright; potatoes will tolerate light shade but cropping drops noticeably.

Earthing Up, Watering and Feeding

Once shoots reach about 15cm above the compost surface, add more mix until only the top few centimetres of leaf remain visible. Repeat every two to three weeks until the bag is full, usually by late June. This earthing up protects young growth from frost, discourages green tubers and multiplies your harvest.

Watering is where bag-grown potatoes are won or lost. Bags dry out far faster than open ground, especially felt ones in a sunny corner. Check daily in warm weather by pushing a finger in to the second knuckle. Water thoroughly until it runs from the drainage holes, then leave it alone; little and often leaves the lower compost bone dry while the top looks damp.

Begin feeding once the buds appear. A high-potassium tomato feed at half strength every fortnight suits them well; too much nitrogen gives you handsome foliage and very few tubers. Keep an eye out for aphids in July and pick off any yellowing lower leaves to improve airflow. Blight is less of a problem on a windy balcony than in a damp allotment, but if brown patches spread fast in a wet August, cut the foliage off at soil level and leave the tubers for a fortnight before harvesting.

Harvesting and Getting a Second Crop

For the freshest new potatoes, start rummaging about ten weeks after planting. Slide your hand down the side of the bag and feel for tubers the size of a hen's egg, taking a few from each plant and leaving the rest to swell. This "bandicooting" keeps the plants growing and gives you repeated small pickings across several weeks.

When the foliage yellows and flops, stop watering and leave the bag for ten days. Then tip the whole thing onto a tarpaulin and lift out your crop. Home-grown tubers bruise easily, so handle them gently and let them dry in the shade for an hour before storing. They will keep for weeks in a cool, dark cupboard in a paper sack — though in most small gardens they vanish long before that.

Once the bag is emptied, don't waste the compost. It is perfectly good for a late sowing of salad leaves, winter spinach or spring bulbs. Rinse the bag, let it dry, and store it flat for next year. Grow two bags in succession, one planted in March and another in June, and you can be lifting fresh potatoes from a patio well into autumn.