How to protect your poly tunnel greenhouse from strong winds

Having a high tunnel greenhouse is a blessing for most gardeners. It allows us to expand our growing season considerably, or even grow all year round in some areas, and it also gives us the chance to grow things that wouldn’t otherwise fair well in our local climate. However, installing a polytunnel greenhouse in a windy area does raise some concerns. Here, at the Lost in Valhalla homestead, we have occasional storms with wind gusts way above 100km/h (60 mph). Nothing too crazy, but enough to require us to properly secure and protect our poly high tunnel from strong winds.

Our new high tunnel greenhouse

Like most other gardeners out there, we’re constantly expanding our growing areas with each passing year. We also like to test things out before scaling up, and this can be clearly seen in our greenhouse purchases over the years. We even owned a tiny plastic greenhouse back when we were growing vegetables on our balcony. We scaled up to walk-in plastic greenhouse last Fall, but come Spring, we stumbled upon a high-tunnel greenhouse at our local hardware store, and we just bought it on the spot.

We didn’t go for the largest size they have, as we felt that 18 m2 (194 sqft) was enough for our current needs. The high tunnel came as a kit, with some easy to follow instructions on how to put everything together. The greenhouse frame is made out of galvanized pipes and the kit provided the plastic tarp as well. The plastic cover is green and has some insertions in it to make it stronger and to offer some shade for the hot summer months. It has windows on either side and one door that opens and closes using zippers.

Installing the greenhouse

Before we started putting together the greenhouse we spent about two weeks planning the location and orientation of the high tunnel. Our property is surrounded by hills and tall old trees. We needed to find the sunniest spot, that was still close enough to our house, water supply and compost area. We had a little snow during this planning phase and that really helped us see which areas were getting the most sun from the late winter, early spring sun.

We also carefully considered our prevailing wind direction and the storm wind direction, which are not the same in our case. The spot we chose had to be next to our orchard to use the trees as protection from the strong winds. For orientation, we chose to align our tunnel on the East-West direction, since that way all parts of the greenhouse will get equal amounts of sunlight at our latitude.

We’ve then marked down the exact spot and staked out a 3 m x 6 m (10 ft x 20 ft) perimeter. Using our trusty rototiller we then tilled two beds on the inside of the tunnel, leaving a narrow path in the middle. We did this to dig into the grass turf and prepare the area for creating a nice weed-free space. This will be the last time we’ll till this area, as I can’t go inside with the rototiller. From now on, we’ll build those garden beds up with layers of compost. The path in the middle will be covered with cardboard to smother out the vegetation there and prevent it from spreading to our beds.

Following the instructions from the greenhouse kit, we fasted together the frame and placed it at its final resting space, over the freshly tilled area. We resisted the temptation to add the tarp right away because we needed to make sure our green won’t blow away at our next storm. Our smaller walk-in greenhouse wasn’t as lucky when it went through its first storm. But we learned our lesson and we added some weights on the bottom shelf and tied it better to the ground using some string, which seemed to do the trick.

Wind proofing our high tunnel

Before we added the plastic tarp, we wanted to firmly secure the frame to the ground. We drove 10 wooden stakes (we actually used some old boards) about 50cm (20 inches) to the ground next to each of the tunnel’s arches. Then, we used some zip ties to secure the high tunnel frame to the posts we’ve put in the ground.

Once the weather turned for the best and we nice a nice day without any wind and plenty of Sun, Greti and I worked together to pull the plastic tarp over the greenhouse frame. We dug a small trench on all sides of the greenhouse and we buried the excess plastic in the ground to prevent any wind getting inside the tunnel. After waiting for a couple of hours for the plastic to warm up and become more flexible, we stretched the poly as hard as we could, pulling from different sides of the same arch.

The tighter the plastic is around the frame, the more it’s protected by wind gusts. We used some U-shaped wires to pin the stretched plastic in the trenches then covered them with the dug-out soil. Next, we tied the plastic sheet to the greenhouse frame from the inside. If you don’t get strong winds where you live, this should be enough, but in our case, we also tied a few strings over the plastic sheet between each arch and tied it to some more wooden stakes.

All these measures, plus careful planning of where to put our greenhouse will ensure that it will survive even stronger winds than what we’ve seen so far. And since this is a big investment for us, I’m happy to know that our greenhouse will be safe. We can’t wait to start some early crops inside this spring and by summer we want to use it to grow some of our tomatoes, hot peppers and peppers. If everything goes well we’ll even try to overwinter some crops, but before we do that, we also need to protect our greenhouse from big snow loads, but that’s for another time.