For the first three years of my gardening 'career' I grew without polytunnel, although we did have a tiny greenhouse. We managed ok, we used low tunnels and cold-frames to great effect and by the third year we were self-sufficient in veg and seasonal fruit all year round. I've covered the general range of options for growing under cover in the basics section of this eBook.

However when we got a polytunnel, everything got so much better. Not only were we able to grow more food and a wider range of food, but more importantly we had a lot more fun doing it. The polytunnel is such a lovely space to spend time in! It's also a great space to retreat to in winter, to warm up, shelter from the rain, or chill out and have lunch.

This section of the book is a celebration of polytunnel growing!

About my polytunnel

https://youtu.be/OxsDFpRbOto

My tunnel is 20 ft by 10 ft and we bought it from First Tunnels, this is the biggest tunnel that would fit on my plot. I really do recommend getting a big tunnel, the small extra cost is really worth it! We live in a windy area, so it has extra thick tubing and wind bracing and I added crop bars in the roof which have been brilliant. My favourite crop for the roof is strawberries in hanging baskets in spring, tomatoes in spring and lettuce in winter!

My tunnel is oriented east/west and it has double sliding doors at both ends, it's not heated. There are a few issues to cover when deciding how large a tunnel to get, assuming you have the space:

  1. Normally as the size of a tunnel increases, the marginal cost reduces, that means for example that if you double the size of a tunnel, the cost might only increase by 50%, rather than 100% and the bigger you go, the lower the increase. However the harvest value increases at a faster rate, as the tunnel gets bigger, by which I mean that if you double the size of a tunnel, you will probably triple the size of the harvest.
  2. Can you keep it cool in summer, this is very difficult in big tunnels. A big tunnel will always be too hot in summer unless you do something to manage the heat, you have the following options:
    1. big double doors at both ends
    2. roll up sides
    3. roof vents
    4. shade cloth or similar (but this will also reduce light levels as well as heat)
    5. big fans
  3. Conversely a big tunnel will be warmer in autumn, winter and spring than a smaller one during the day, it will cool down slightly slower at night, but it will eventually dip to the same temperature as a smaller tunnel. A big tunnel is however often easier to fleece, because you have more space to move around. In a big tunnel you could for example reserve the central bed for tender crops that need fleecing and if you have paths on each side, this will be very easy to lay down and remove. Even in spring and autumn you will find your tunnel gets too hot, unless you can open the doors during the day
  4. Can you water it? A large tunnel needs an enormous amount of water in summer, the larger the tunnel the more time you will spend watering unless you have an automated system. If you are on an allotment you also might not have water from late autumn until mid-spring, so you will need to collect a lot of water too. You can collect water off a tunnel (see below) some suppliers supply integrated gutters
  5. Do you need the space? In autumn, winter and spring a tunnel is wonderful, if you intend to grow food all year round, the larger the tunnel the better, almost everything will grow well in it. It’s just a wonderful space to spend time in, humans love it, plants love it just as much, provided it’s ventilated. However if you just want it for summer crops then it’s not always ideal unless as I mentioned you can manage the heat. Peppers and tomatoes don’t appreciate too much heat in summer, cucumbers like it more. I find most crops do as well outside or under low tunnels and cold-frames as they do in a big tunnel in summer and these are much easier to manage
  6. If you are in parts of Ireland or Scotland though, where it rains a lot and is often cloudy and/or frosts are late and early, you will definitely benefit from a tunnel in summer

Capturing water

One of the downsides to a polytunnel and especially a big one is that you will need to water it a lot and if you are on an allotment you will almost certainly need to capture water off the tunnel and store it up for use in autumn, winter and early spring when the allotment water supply is off.

I've used two different techniques for capturing water, both work. This is the first attempt.

https://youtu.be/LuLloAEcaMg

This is my second attempt, which I much prefer, as it's more stable and as a result puts less strain on the adhesive holding the plastic to the tunnel and gutter.