How to Grow Potatoes on a UK Allotment: Complete Guide

Potatoes are the perfect allotment crop. They're forgiving for beginners, produce heavy yields, help break up new ground, and there's nothing quite like digging your first harvest — like finding buried treasure. This guide covers everything you need to know to grow excellent potatoes on a UK allotment, from choosing varieties to curing and storing your crop.

Choosing Potato Varieties for a UK Allotment

Potatoes are divided into three groups by harvest time. First earlies are planted March–April and harvested June–July — they give you new potatoes, the first fresh harvest of the year. Second earlies follow 2–3 weeks later and are harvested July–August. Maincrop potatoes are planted in April and harvested August–October; they produce the largest yields and store best.

Recommended varieties for UK allotments: First earlies — Rocket, Swift, Pentland Javelin. Second earlies — Charlotte, Kestrel, Nicola. Maincrop — Desiree, King Edward, Maris Piper, Rooster. For blight resistance (important if you've had problems): Sarpo Mira and Sarpo Axona are exceptionally resistant.

Always Buy Certified Seed Potatoes

Always buy certified seed potatoes rather than using supermarket potatoes. Certified seed is guaranteed disease-free, which matters because potatoes carry several serious soil-borne diseases that persist for years. Supermarket potatoes may also be treated to prevent sprouting. Seed potatoes are available from late December from suppliers including Suttons, Thompson & Morgan, and Kings Seeds.

How to Chit Potatoes

Chitting means letting your seed potatoes sprout before planting, giving them a head start. It's optional but particularly useful for first earlies where you want the earliest possible harvest. To chit: stand potatoes rose-end up (the end with the most eyes) in egg boxes or trays, in a cool, frost-free, light spot. Leave for 4–6 weeks until you have short, stubby green shoots 1–2cm long.

Avoid long, pale, spindly shoots — these are etiolated from too much warmth and too little light and will break off. If your shoots have become too long, move to a lighter spot and they'll gradually toughen up.

When to Plant Potatoes in the UK

The traditional guide is to plant first earlies around St Patrick's Day (17 March) in the south, or Good Friday in the north — but soil temperature matters more than the calendar. Potatoes need soil that's at least 7°C and not waterlogged. In most of the UK, first earlies go in late March, second earlies and maincrops in April.

How to Plant Potatoes

Dig a trench 10–15cm deep. Place seed potatoes shoots-up at the correct spacing: first/second earlies 30cm apart with 60cm between rows; maincrop 37cm apart with 75cm between rows. Cover with soil. If frost is forecast after planting, a layer of fleece over the bed will protect the emerging shoots.

Earthing Up: The Most Important Job

Earthing up — drawing soil up around the emerging shoots — is one of the most important tasks with potatoes. Do it in two or three stages as the plants grow, building up a ridge about 20–25cm high. Earthing up does three things: protects shoots from late frosts, prevents tubers from being exposed to light (which turns them green and poisonous), and increases yield by giving tubers more room to form.

Watering and Feeding Potatoes

Potatoes need consistent moisture, especially once they start flowering — this is when tubers are forming and irregular watering causes scab, hollow heart, and poor yields. Water deeply once or twice a week in dry spells rather than lightly every day. Avoid waterlogging. If you added compost or well-rotted manure before planting, extra feeding is rarely needed.

Potato Blight: How to Prevent and Manage It

Blight (Phytophthora infestans) is the most serious threat to outdoor potatoes in the UK, particularly in warm, wet summers. It spreads rapidly and can destroy a crop in days. Prevention is the only real control: space plants generously for good airflow, water at soil level not on foliage, and choose resistant varieties if you've had problems before.

If blight strikes, cut and remove all top growth immediately, wait two weeks, then harvest the tubers. Any tubers left in blighted soil will rot. Never compost blighted material — bag it for the council waste.

When and How to Harvest Potatoes

First and second earlies are harvested once the plants flower and the haulm (top growth) starts to die back. Gently dig under the plant with a fork to find the tubers. Maincrop potatoes are left longer — until the haulm has died back completely, usually August–October. Allow maincrop potatoes to dry on the soil surface for a few hours before storing to cure the skins.

Storing Potatoes

Store maincrop potatoes in hessian or paper sacks in a cool (4–10°C), dark, frost-free place. Never use plastic bags — they trap moisture and cause rot. Check regularly and remove any that are sprouting or rotting before they infect others. Well-stored maincrop potatoes keep for 4–6 months.

Frequently Asked Questions

Can I grow potatoes in the same bed every year?

No — this is one of the golden rules of allotment growing. Rotating potatoes prevents the build-up of soil-borne diseases including blight and scab, and the potato cyst nematode. Leave at least 3–4 years before growing potatoes in the same ground.

How do I stop potatoes going green?

Green potatoes contain solanine, which is toxic. They turn green when exposed to light. Earth up well during the growing season and store in complete darkness. Never eat green potatoes.

Why are my potatoes small?

Small potatoes are usually caused by: not earthing up sufficiently, irregular watering during tuber formation, overcrowding, or harvesting maincrops too early. For bigger yields: earth up well, water consistently once flowering starts, and leave maincrop varieties until the haulm dies back fully.