Growing Exclusively in Polytunnels

The recent weather and crop massacres have made me give serious consideration to how I could alleviate both issues. When there is so much to be done, but it’s simply too wet to do anything, you can’t help but feel the season is slipping away from you.

More frustrating is that much of what has been planted has been consumed by birds, slugs and insects. This year, nothing has been saved – if it’s in the ground, it seems to be fair game.

It’s clear I need to better protect my crops, regardless of whether history tells me they could be targeted or not.

Over the last few days, I’ve given a great deal of thought about how I can do this.

Hoops and Netting

I’ve considered simply adding hoops and netting to each bed, which is what most people do. There are, however, several issues I have with this. Firstly, unless you buy the more expensive ‘off the shelf’ net tunnels with access hatches, they are very fiddly to access adequately. Especially if they’re secured well enough to keep off the pests you’re protecting from. I’ve used this approach in the past and found it such a hassle that weeding became a daunting task. It does, however, work.

Timber Frame Covers

Rather than using hoops, most fellow plot holders on my site have opted for timber frames with netting stapled to it. This typically is more robust, it appears, and as long as the frames aren’t too big, they are simply lifted off. In theory, a frame could be built on a hinge to make this even easier, which I know a lot of people do for strawberries.

The problem with this approach, however, is height. A frame big enough to protect crops such as corn or sprouts would simply be too big and heavy.

Walk-In Cages

Encasing the entire 500sqm plot as a walk-in cage was my preferred option – until I priced up the timber. I initially looked at some of the ‘off the shelf’ products, but at this size realised that unless I match 6 numbers this week, it’s not going to happen anytime soon.

Setting aside the time and skill required to build such a structure – and allowing for various ‘doors’ that would need to be placed within it to allow for different types of netting – it became apparent that it was neither cost-effective nor likely to be a quick process.


Inside a productive Polytunnel

While all of the previous solutions would work in terms of managing pests, none solve the issue of the weather. As much as I enjoy time on the plot, none of us really like working in the rain or snow. While a polytunnel during winter won’t stop me getting cold, it will at least keep me dry – and that is half the battle during winter.

Many people leave their plot at the end of Autumn and don’t return until Spring. Aside from a few, that’s very much the case on my site too. Personally, I like to be there as much as I can. For me, there is always something to be done.

I already have two polytunnels – both 3m x 2m. They have been a very useful addition, especially in these early stages of developing the plot. They’ve kept me sheltered from the weather, allowed me to get seeds going and doubled-up as a storage shed for the time being.


As I’ve yet to get either a dedicated shed or greenhouse, they’ve both very much worked overtime. Both are now crammed full of both plants and general odds and ends. As I’m in the process of building my shed base, most of the materials are in them – which means there’s little space for me to actually get in there!

Ordinarily, if I was following my original intended route of growing outside in the ground, these two polytunnels would have sufficed. Coupled with a greenhouse for seed starting, they are big enough to accommodate a dozen or so tomato and cucumber plants.

At 3m by 2m though, there’s little space to manoeuvre when you start planting in them. It really is a case of space to tend and water, but little else. To fulfil my objective here fully, I’ll need bigger tunnels.

The Options

There are a huge number of polytunnels available. You can spend as little as £40 for a small one, or tens of thousands for a really big one. As nice as the ‘semi-pro’ or ‘hobby’ models from specialist suppliers are, they’re still outside the price range of most allotmenteers – myself included. Having looked at dozens of options, 6m x 3m would appear to be the right balance between size and cost. These are big enough to be useful, but ‘cheap’ enough to justify.

Frame Considerations

The two polytunnels I already have cost £60 and £80 new. The more expensive one has a metal framed, hinged door and 25mm tubing. The cheaper of the two has a zip-up door and 16mm tubing. While I’ve learned that the zipped ‘central’ door allows for better use of space (you can easily use either side), the size of the tubing makes a huge difference. The cheaper tunnel has a tendency to ‘rock’ in high winds and needed much more robust anchoring. The more expensive one with the larger tubing, though still well anchored, barely moves at all – even in gales.

So, a minimum of 25mm tubing I would consider essential, especially at larger sizes. Additional crop bars could be added to further strengthen the frame. They are rarely provided at the budget price point, but are fairly cost-effective to buy elsewhere. Importantly, they only appear to be available for tubing 25mm or above.

Ventilation Considerations

If the polytunnels are to be used for virtually all crops, then consideration needs to be given to ventilation and cooling too. While they may only provide an extra degree or two during the winter months, during summer they can easily exceed the level of heat most crops are comfortable with. While most offer ventilation ‘flaps’ either side of the cover, which do help, they won’t provide enough cooling for many crops you’d usually plant outside.

There are however some polytunnels available that have doors at either end. Opening these, combined with the side ventilation, I expect would provide a decent balance.

Of course, leaving the doors open also means access for the very pests I want to keep away! The solution to this is potentially to add a timber frame at either end, into which a door could be fitted. This frame could be netted, and potentially also adds to the overall strength of the structure. This approach would limit me to the ‘zip-up’ style doors, but fortunately, they tend to be cheaper anyway. The advantage with this, however, is that I can be more flexible – the poly doors can be down during winter, and left up over summer.

With the addition of timber-framing for the doors, and timber-edged beds AND crop bars, I could make maximum use of both ground and vertical space. Potentially, I’d have more growing space than had I stuck with beds outside.

Pretty Plot versus Productive Plot

As crazy as it may sound, this is the element I’ve battled with all week. Having an ‘attractive’ plot is fairly important to me. Partially because I share a great deal about it here and elsewhere. But more importantly, because sometimes it’s nice to simply sit back and enjoy it. However, there’s nothing attractive about empty beds, slug-munched leaves or battered crops. I’d sooner be harvesting than admiring.

Realistically, I’ve also reflected on what I’m growing or want to grow. I consume many salad leaves, which polytunnels would allow me to grow year-round. I participate in the growing of experimental, unusual, often tender, crops too. I’d like to be able to do more of this too, but to do this sufficiently I need a little more control of the conditions. Polytunnels, in theory, would allow this. A huge number of such crops have already been lost this year due to either weather or pest damage.

As part of my research for this post, I spent some time looking for examples of how polytunnels had been integrated into a garden or plot in an ‘attractive’ way. There are a huge number of examples of attractive interior layouts, especially when in full growth. However, I couldn’t find a single example of exterior integration. I have a few ideas of how this could potentially be achieved, but it’s far from the priority right now.


Finally, aside from cooling and ventilation as already mentioned, the other challenge is water. Clearly, polytunnel crops can’t rely on rainwater. So, watering has to be done manually. Or via some kind of irrigation or self-watering system. As our site doesn’t have mains water, this could potentially be problematic. However, one advantage polytunnels (and greenhouses, and sheds…) do have is a means to collect water for storage. It’s a little trickier to accomplish with a polytunnel than say a shed or greenhouse, but perfectly ‘do-able’. This, combined with the two reservoirs we do have on site, should ensure water shortage isn’t too much of an issue. I would, however, have to ensure I have as much storage capacity as possible – and ensure my layout accommodates it.

I know of other plot holders – including one on my own site – that do most of their cultivation undercover alone with few problems. In terms of making the most of our ever-changing weather patterns, and extending the growing season by a month or two, it almost seems like a logical thing to do.

Do you grow everything under cover? Have you found any challenges I haven’t considered? I’d love to hear more!

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