I’ve had my own polytunnel for a little over 6 months now, and it’s seen plenty of different extremes in weather – including some particularly blustery conditions. I’ve also moved it once, which means anchoring it twice.
There are a few different ways of anchoring, some work better than others. It can be as simple as digging the frame into the ground, or as elaborate as using anchor plates or concrete. My chosen method has proven itself to be both effective and relatively easy – without being ‘permanent’.
Securing the Frame
I use fence post spikes in each corner. Once these are in place, cable ties are attached to the base frame of the polytunnel. For assurance, I use either 2 or 3 cable ties in each post – in case one fails, though it hasn’t happened as yet.
It can take some effort getting the posts in the ground, and you’ll definitely need a hammer of some kind – but once in, they are solidly in place.
If the ties are tightly in place, once all 4 corners are done, absolutely nothing will move the frame – and I’ve deliberately tried moving it by hand a few times! The advantage of doing it this way is that not only is it effective, but it’s also relatively easy to undo when you need to. All without leaving behind chunks of concrete!
Securing the Cover
Of course, that only secures the frame. Most covers (mine is a single piece, shaped cover – as most ‘smaller’ polytunnels are) are secured to the frame using fabric ties on the inside. These are tied around the frame and into a knot. If you’re fortunate, yours will have quite a lot of these. These certainly help, but I have found in the past they have a habit of loosening over time. As they loosen, the cover can begin to lift, which puts extra strain on the remaining ties.
Fortunately, most covers have a little extra at the bottom – a ‘skirt’, if you like. Most people dig a small trench around the frame, insert this skirt into it and re-cover with the removed soil. I’ve found this to be effective. If that sounds like a bit too much effort, you could instead place some slabs or heavy stones on top of the skirt. But be careful not to rip the cover, which is surprisingly easy to do.
Ensuring your tunnel stays where you want it, and not on a neighbouring plot, relies on the quality of the frame too. If you have a relatively weak frame, the kind that is assembled by ‘pushing’ parts together, rather than screwing – then it’s worthwhile trying to strengthen the frame a bit. Having had a few of those over the years though, it’s somewhat inevitable that at some point the frame will fail. If you haven’t purchased yet, I’d strongly recommend ensuring you have a strong, and heavy, frame to start with.
Regardless of how you choose to anchor your polytunnel, it’s also worth putting some hotspot tape between the frame and cover – this helps the cover last an extra season or two.