A polytunnel is my lifeline to a longer growing season and tender summer veg. It opens up possibilities I could never enjoy when living in higher, more marginal ground.

In warmer sheltered parts of the country, a tunnel acts just as a greenhouse does for me. But, in a balmier spot, you’ll need to be sure the temperature or humidity level isn’t too high. Ideally you’ll have a dryish atmosphere that reduces the risk of blight developing on tomato foliage and guarantees a fine ripe crop of peppers, chillies and aubergines.

At 200 metres, I grow fast-maturing bush tomatoes, sweetcorn and cucumbers which I’d find impossible outdoors. And overwintering endives, lettuce and chard stand a much greater chance of pulling through an icy spell.

My beds are never empty: they’re the only ones that give me 2 or 3 crops a year. So, wherever you live, if you’ve the space, start the year by planning for a new tunnel.

You may not have much choice about where to locate your new toy, but, ideally, look for a sheltered, sunny place. Tunnels can and do take some battering, but severe gusts will distort the supporting ribs, thereby putting pressure on the polythene skin.

The structure gets best protection when the narrow entrance directly faces the prevailing wind, and plants benefit when the long side is south-facing. The base must be absolutely level, and preferably not on a slope. But mine hasn’t come to too much harm with a slight front to back gradient. A final consideration is the water supply. For many years, I ran a garden hose from an outside tap quite successfully, but had the tunnel piped when the yard was relaid a few years ago - bliss.

Erecting a polytunnel is highly skilled, requiring at least two people, so, unless you’re a DIY expert and have a meticulous eye for detail, I’d recommend engaging a professional. I found even replacing the skin after last winter’s snow was pretty demanding, especially as winter gales had slightly distorted one of the ribs.

Water, weeds and wind are the points to consider when running a polytunnel. Although the structure needs to be protected against the weather, some air circulation is essential as it guards against fusts and helps control temperature. A still atmosphere makes 50C perfectly possible on a fine, summer’s day. And overnight winter temperatures are often 2C lower in a tunnel than outdoors.

I increase ventilation by having ‘stable doors’ at the front, with the upper door open throughout the summer, and the lower one closed to exclude questing poultry beaks. I raise or lower a fixed sliding door at the back of the tunnel to also help control temperature and use it to nip out with a weed bucket to the tunnel’s compost bin.

I’ve tried every conceivable watering system over the years: drip irrigation from a header tank; under soil leaky hose; and the trusty watering can. The drip system is self-regulating and the leaky hose is fine when you’re around but it could also be controlled with a timer. But I’ve come to favour a hand hose, because I can monitor how plants are growing and how much water they’re needing. Though it’s also very relaxing to gently sip a pint of home brew, while pretending to be doing something useful.

This hand watering also lets me notice the progress of unwelcome weeds, for they enjoy the benefits of tunnel life as well. A mulch keeps them at bay. I cover layers of newspaper with grass clippings and top them up till the plants close canopy, taking care the grass doesn’t touch and scorch stems.

Plant of the week

Sarcococca confusa. On a mild winter’s day the tiny white flowers fill the garden with sweet scent. An evergreen shrub with box like leaves. Needs a shady site protected from the harshest frosts.