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  • Posted March 8th, 2015

    Putting up a polytunnel: fresh fruit & veg all year round

    Putting up a polytunnel: fresh fruit & veg all year round

    There’s loads of information around when you come to put up your polytunnel. The one I’ve just finished erecting came with really good instructions and the company website provides a whole host of instructional videos for the fiddly bitshttps://www.firsttunnels.co.uk/tunnel_vision.asp.

    I should say that putting up polytunnels is nothing like riding a bike or swimming. Years ago, when I worked as a grower on organic farms, I put up some really big tunnels, but I shouldn’t have thought that that necessarily stood me in good stead for avoiding all of the potential pitfalls this time around.

    So, never try to put up a tunnel on your own. I already knew this. I really did. But this was only a small tunnel, right?

    And when you do have help, as I did for putting on the plastic, try to get one more person than you think you’ll need. It’s well worth having to buy the extra pint or hand over the extra bag of veggies just for the extra pair of hands on the team.

    I found myself wrestling with hoops and desperately wishing that I had someone to hold the other end of the tape measure. There is no way to be as accurate when you’re on your own and especially on an imperfect site – which is what you’ll have unless you’re putting up your tunnel on a flat lawn – the job can very quickly become a sort of firefighting exercise correcting problem after problem.

    polytunnel interior

    Also, make sure that you have all of the tools you need. Make the instruction booklet your bedtime reading for a night. Write a list. If in doubt, take an extra spanner and a range of screwdriver sizes.

    Charge your drill!

    Setting out is the most important stage. A polytunnel is easily put together, but don’t rush the preliminaries. It’s only a tunnel, and I’m a great believer in the “close enough for a country job” philosophy, but you’ll have to look at the off-centre ridge for a long time once it’s up. And yes, my new tunnel does have an off-centre ridge!

    Struggling with hoops is one thing, but even an imperfectly erected tunnel will transform your growing. Propagation space and four season gardening are invaluable advantages of tunnels. As a small scale grower I know that the productivity of my garden is multiplied enormously by even a modest tunnel space.

    The value of protected cropping can be easily seen by looking at the British strawberry industry, booming thanks to polytunnels. The thing is of course that whilst for growers tunnels can be a godsend, for people who have to look at them they can be a glaring eyesore, and we all have to wonder about the polythene. I’m supposed to be an environmentalist, what am I doing using a vast sheet of polythene?

    polytunnel front

    Polythene is made from crude oil in a gasification process. It’s not nice and it’s certainly not sustainable. When we’re done with our polytunnel cover, five years down the road or so, it has to be disposed of. Fortunately, at least these days it can be recycled: http://www.solwayrecycling.co.uk/farm-waste-recycling-system/polytunnel-recycling but nonetheless, this kind of protected cropping is energy intensive.

    So growers will argue that their tunnels reduce food miles, and also that they allow for less use of fungicides and pesticides. For me it’s about making my small garden a viable business proposition, well, that and the delights of good winter salads and reliable summer tomatoes. Still, I wouldn’t deny that polytunnels are problematic: they most certainly have an environmental impact and above all they are noticeable in the landscape.

    One of the things we can do as tunnel users is try to place them where they will have less visual impact; we can also use plantings to hide them. I’ve nestled my tunnel up against a wood, and I’ve planted trees around my garden; it’s still quite visible now, but eventually it will be much less so.

    Protected cropping has always been energy intensive. It’s instructive to look at a walled garden; there’s a lot of bricks and mortar in a walled garden. Also walled gardens were traditionally built with big greenhouses, glass and iron all along their interior south-facing wall. In the days when walled gardens fed whole estates, they used tons of manure every year and enormous amounts of labour. I don’t mean to suggest that polytunnels will ever be seen as beautiful things, but it would be interesting to know if anyone ever complained about the visual impact of a walled garden.

    I have friends who talk about using glass instead of polythene and there’s nothing I’d like more than a big greenhouse, preferably in a walled garden. Cost of course, is prohibitive. In any event, if we take energy descent seriously, greenhouses and vast enclosing brick walls are barely more of a long term solution than polytunnels.

    polytunnel door

    Polytunnels are a transitional technology, in my opinion best seen as a way to get us through a few years during which we establish durable food growing systems. This argument necessitates some other more sustainable strategies for season extension. What could those strategies look like? When the last skin is taken down from the last polytunnel what are we going to do?

    Well, we might perhaps at least come up with interesting ways to use the frames, clad them with planks or weave willow in amongst them and thatch them with reed. But as for the advantages of protected cropping, we will need to design for the creation of warm microclimates. If we don’t want or can’t have tunnels, then we’ll need to use courtyards, hedges and windbreaks; we’ll need to use pond placement to warm and to light our sheltered spots, and every wall will have to lend its thermal mass to growing.

    Designing microclimates to replace expensive and energy intensive methods of protected cropping is a really exciting challenge; it can also be expensive and energy demanding to put into practice in the first place. This is the puzzle of transition, and we all need to be thinking about it when we’re enjoying stepping out of the March wind into the Mediterranean warmth of our polytunnels.

    The views expressed in our blog are those of the author and not necessarily lowimpact.org's


    • 1Peter Richardson March 17th, 2015

      I’m not sure that we need to think about polytunnels as a transitional thing that we can’t really have in a properly green future. The metal poles last for decades and are fully recyclable. The polythene covers are recyclable, and I’ve not got the figures but I suspect the amount of oil and energy that goes into producing a polytunnel cover is tiny compared with the oil and energy it saves by reducing food miles. We do have to eat – whereas we don’t need half of the things that oil and and energy are currently wasted on. Could there be a long-life non-oil-based covering material developed as an alternative to polythene? You bet there could if it was something required by the military rather than just by the people who feed us!

      I put up my first polytunnel last year. It’s fabulous, I love it – yesterday was a dull and chilly 8 degrees outside, and a snug 18 degrees inside. My experience was similar to yours. I put up the 12 x 15 foot frame 99% on my own which took days and was much harder than expected, especially the setting out and levellng on my sloping site. Mine was also from First Tunnels – yes their instructions are very good but a bit overoptimistic. Their advice was to allow a weekend to put up the whole tunnel – as a novice polytunnel builder (but experienced DIYer) it must have taken me 4 or 5 days to erect the frame and doors. I had a big crew for the covering, including someone who’d done it before, so that was OK but it took us most of a day.

      After I’d completed it, there were a couple of tips I felt like publishing in the hope of helping others, so here goes:

      1) don’t expect the self-drilling screws to self-drill into the steel tubes. I found it necessary to pre-drill a small hole first, and even that was difficult as the drill bit kept skating off the round tube. In the end I found that a masonry drill bit was best for making a dent in the tube, followed by a sharp HSS (metal drilling) bit to make the pilot hole, followed by the ‘self-drilling’ screw!

      2) First Tunnels didn’t mention in their 50 page instruction manual that the hoops are not quite symmetrical when assembled. So you have to get them all the same way round (socket joints facing the same way) or the hoops won’t line up.

      Growing-wise, the tunnel has already been a great success and I’d hate to be without it. Loads of tomatoes and melons and cucumbers last summer, and salads this winter. I’m also raising tomato/courgette/squash/cucumber plants to sell, so I’m pretty sure the tunnel will pay for itself in 2 or 3 years.

    • 2Paul Jennings March 17th, 2015

      Thanks for the response, Peter.

      I suppose that in terms of whether polytunnels will prove to be a transitional technology, a lot depends on how steep and how severe we expect energy descent/collapse to be. I’m rather afraid that it may simply prove impossible to keep polytunnels, but of course I hope I’m wrong because, as you say, they’re great!

    • 3Oscar March 30th, 2015

      I’ve put up a few tunnels. Some tips. You need to drill a pilot hole for self-tapping screws, the hole should be nearly as wide as the thread of the screw. An engineer’s punch and a good thump with a hammer will make a hole to hold the drill bit and stop it skating around the hoop as you are starting. A calor-gas or parafin heater (more energy) in the tunnel will warm the plastic enough to get one last stretch out of it before fixing the final tension, making it nice and tight over the frame. You need as many people as you can get, on as sunny and still a day as you can get. And you can zip-tie a six-inch nail to the end of your tape measure to give it an anchor point in the ground as you try to lay out by yourself.

    • 4Paul Jennings March 30th, 2015

      Thanks Oscar, always good to get a few tips. First Polytunnels self-tapping screws were really easy I must say and gave me no bother at all. The heater is a really good idea and I always try to wait for a sunny day if I can. I think most of all I lacked people……………….. and a 6-inch nail – that is a really good idea! ?

    • 5John Harrison March 31st, 2015

      It’s quite possible to grow enough vegetables to sustain us without greenhouses or polytunnels and to store crops to cover ‘the hungry gap’ without freezing. However, your tunnel will allow you to grow a much wider range of crops over an extended season. The covers are often guaranteed for 5 years but a decent cover will usually last twice that, so it’s only half as bad as you thought!

      My pet plastic hate is those who cover plots with black plastic to supress weeds and to grow potatoes under. No way I could justify that.

    • 6John Lightfoot April 1st, 2015

      Out of interest, what is the green part of the Polytunnel ?

    • 7pdjennings2014 April 1st, 2015

      It’s a mesh over a wind-up vent all along that side. Very useful for controlling the conditions inside the tunnel.

    • 8John Lightfoot April 1st, 2015

      Growing in a poly tunnel in the UK is not the best thing, poly tunnels have huge temperature swings compared to a glasshouse. Saying that they can be super things for extending the seasons and allowing you to grow items that otherwise would be difficult. If you are buying new a poly tunnel can be quite an investment, if you have a reasonable plot of land and can club together with some friends a proper glasshouse would serve you a lot better. Quite a lot of nursery’s are closing down or upgrading and glasshouses come up at silly low prices because of the labour costs to dismantle, transport and erect at a new place, but if you have a group of you those costs would be low and you would get far better results. I bought a dutch frame glasshouse 40′ x 140′ for £600 ,

    • 9Terry K April 7th, 2015

      Interested to hear about the wind-up vent with mesh, particularly as I was shocked to find a friend with a West Devon smallholding had dispensed with his polytunnel and replaced it with a greenhouse because the polytunnel got too hot.

      I am about to erect a 35 yr old greenhouse which has never been put up. Fingers crossed!

    • 10pdjennings2014 April 7th, 2015

      Good luck with that Terry!

      Yes, tunnels can be very well vented these days and vents can certainly be retro-fitted on to old tunnels.

    • 11Izzy Darbishire April 15th, 2015

      Hi can I ask, did you get the glasshouse from a nursery? We have been looking on eBay but they are mostly too small or too expensive if big enough and we are now on the verge of making a DIY polytunnel. We’d still have to buy the plastic new though, as I imagine piecing together old pieces of plastic wouldn’t work.

    • 12John Lightfoot April 15th, 2015

      Register at a few estate agents that handle nursery sales. They go cheap because usually they want them offsite asap. Gather together loads of friends to dismantle and take away. Remember that usually you can buy one that is too big and just put up as much as you need so do not be put off if the glasshouse is the wrong size. Also do not underestimate the massive weight of the glass that needs to be transported. Need any more info just ask.

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