Polytunnels for an allotment: are they worth it, and what to look for

If a greenhouse is a jewel box, a polytunnel is a workhorse: far cheaper for the space, quick to put up, and big enough to walk into and grow proper rows under cover. It buys you weeks at both ends of the season, shrugs off the worst of the weather, and finally makes outdoor tomatoes, aubergines and melons a realistic prospect in a cool British summer. For an allotment, pound for pound, nothing else gives you as much.

The trade-offs are honest ones. The cover (the polythene 'skin') needs replacing every five years or so. It needs good ventilation or it bakes. And it absolutely must be anchored properly, because a tunnel that catches the wind wrongly can be destroyed in a single gale. Get those three things right and it'll repay you for years.

Frame: thicker steel tubing stands up to wind far better than the flimsy poles on the cheapest pop-ups — worth paying for if it's staying up year-round. Cover: look for UV-stabilised, anti-drip ('anti-fog') polythene, which lasts longer and stops cold drips falling on your plants. Doors at both ends give you the cross-flow ventilation that stops it overheating; roll-up sides are better still. Size: taller and wider than you think — you want headroom to work and a path down the middle. And anchoring: ground anchors or a base rail, plus burying or trenching the cover edge, is what keeps the whole thing earthbound.

Not ready for a tunnel? A cold frame or small greenhouse gives you a gentler, cheaper way into season extension — there's a guide to those below.