Growing potatoes in containers: the UK month-by-month guide

Why bother growing potatoes in containers?

Three reasons. First, slugs. The curse of UK ground-grown spuds, barely bother with container plants. Second, the harvest is genuinely theatrical: tip the bag onto a tarpaulin and the potatoes tumble out clean, no digging required. Third, you don't need a garden at all. A single sunny step or patio corner will grow you real food.

The trade-off is yield per plant. A bag plant gives you 0.5–1kg; a well-grown ground plant gives 1.5–2kg. Stack three bags and you've more than caught up, in a footprint of less than a square metre.

Picking the right variety

First-earlies. Plant late March, harvest June. Beat the blight, beat the slugs, beat the weeds. The beginner's category. 'Charlotte', 'Pentland Javelin', 'Lady Christl', 'Rocket'.

Second-earlies. Plant April, harvest July–August. Slightly bigger yields, slightly more risk. 'Maris Peer', 'Kestrel', 'Nicola'.

Maincrops. Plant mid-April, harvest September. Best yields, but real blight risk. Only worth it in containers if you want storage potatoes. 'King Edward', 'Sarpo Mira' (blight-tolerant), 'Pink Fir Apple'.

The month-by-month routine

February

Buy certified seed potatoes from a UK supplier. Not supermarket potatoes, which carry a real risk of disease and weak vigour. Stand them in egg trays, eye-end up, in a cool light room to chit. Aim for 2cm dark green sprouts by planting time.

Late March (first-earlies)

40L bag, 10cm of compost in the bottom, three chitted seed potatoes spaced evenly, eyes up. Cover with 10cm of fresh compost, water once, and place in full sun.

April

Foliage emerges. As soon as it's 15cm tall, add 10cm more compost, this is "earthing up". Repeat every two weeks until the bag is nearly full; it triggers more tubers along the buried stem.

May

The bag is full of compost, foliage thick and dark green. Water once a week unless it's dry. Resist the urge to feed. Potatoes don't need it in good compost.

June

Flowers appear on first-earlies. Once the flowers start to fade, the potatoes are ready. Stop watering for five days, then tip the bag onto a tarpaulin. Sort, eat the lot within a fortnight, or store in paper sacks in the dark.

July–August (for second-earlies and maincrops)

This is the critical watering window. Tubers bulk up during this period, and inconsistent water gives you hollow or split potatoes. Water twice a week, deeply.

September (for maincrops)

Once the foliage yellows and dies back, the crop is mature. Wait two weeks after die-back to let the skins set, then harvest. Store maincrop in paper sacks in a cool, dark, frost-free shed; expect 8–12 weeks of storage.

1. 1

   Use peat-free multipurpose

   John Innes No.3 works too, but it's heavier and pricier. Multipurpose holds water better through summer.

2. 2

   Drainage holes. Check them

   Plenty of shop-bought 'potato bags' have weak holes. Pierce with a screwdriver before filling.

3. 3

   Stand bags on pot feet

   Lifts the base off the ground for drainage and stops slugs climbing in.

4. 4

   Position in full sun

   Six hours of direct sun, minimum. Shadier corners give you thin, leggy plants and small tubers.

Blight in containers

Container potatoes succumb to blight the same way ground plants do, brown lesions on leaves, rapid collapse. The fix: pick blight-tolerant varieties (Sarpo Mira), keep foliage open by spacing bags 40cm apart, and remove infected leaves the moment you spot them. Once blight reaches the stem, cut all the foliage at compost level and harvest the tubers within a week. Leave them in the bag with diseased foliage still attached and you'll spread spores straight into the crop.

The bag potato isn't a compromise. It's the cleanest, easiest, slug-proofest harvest of new potatoes you can grow in Britain.