Storing Potatoes — The Potato Clamp

Harvesting for Storage

Potatoes destined for winter storage should be left in the ground until the haulm (top growth) has died back completely. This signals that the skins have set and will resist bruising and disease in store. Choose a dry day for lifting; wet potatoes store poorly and rot quickly.

Inspect every potato as you lift. Any that are damaged by the fork, blemished with blight lesions, slug holes, or soft patches should be set aside for immediate use. Only perfect, unblemished tubers go into long-term storage.

Green Potatoes

Any potato that has been exposed to light — either in the ground (if earthing up was inadequate) or after lifting — will have developed solanine, a toxic alkaloid that makes the potato bitter and potentially harmful. Green or greenish potatoes should not be eaten. Greening can be prevented entirely by thorough earthing up during the growing season and by storing in complete darkness.

Storing in Hessian or Paper Sacks

The simplest method for smaller quantities is to store in hessian or thick paper sacks (never plastic, which traps moisture and encourages rot). Place in a cool, dark, frost-free building — an unheated outbuilding, cellar, or garage. Temperature should be 4–7°C. Check monthly and remove any that are rotting — one bad potato genuinely will spread to its neighbours.

The Outdoor Clamp

For larger quantities, the traditional outdoor clamp is effective and requires no special buildings. It was the standard storage method for farm-scale potato crops across Britain and Northern Europe before the era of refrigeration.

1. Choose a well-drained site. Lay a thick bed of straw (20–30cm) on the ground.
2. Pile the potatoes in a conical heap on the straw, with the narrowest point at the top.
3. Cover the heap completely with straw (another 20–30cm).
4. Cover the straw with excavated soil, packed firmly. Leave a tuft of straw protruding from the top as a ventilation chimney.
5. In hard frosts, add a second layer of soil or extra straw around the base.

Clamps maintain a stable temperature around 4–6°C through their insulating mass and the slight heat generated by the potatoes themselves. They are surprisingly effective even in severe winters.

Chitting

Potatoes removed from store in late winter for spring planting should be "chitted" — placed in egg boxes or seed trays in a cool, light (but frost-free) place to encourage short, sturdy green shoots before planting. This gives them a head start.