In 2015 I acquired my first portable greenhouse (or as I refer to them sometimes, a pop up greenhouse). Back then I wrote a post about setting up that first one. (Which is worth reading, as I walk through setting up one of these.)
Those blissful years of urban gardening. This one was beautifully set up, where it even had a finished floor.
Now that we live rural, I am not so worried about things looking pretty, but it was worth the work then for the look.
Often in reviews of them the constant complaint is how the wind shreds the greenhouses, and they are destroyed quickly. Over the years I have learned many tricks to make them last longer. Because the portable greenhouses are a (mostly) affordable tool that one needs in microclimates. Particularly on Whidbey Island in Washington State. If you want to have a longer growing season, and produce more food, you need season extenders.
So over the years, even after I got a real greenhouse, I have continued to use these portables. And I have found I can get them to last far longer. I keep the covers on from around February to May, then I make sure they are dry, and fold them up to use the next year. The frames last 3 to 4 years, or more. They will get rusty, but will keep working. If your cover tears, you can get replacements. They might not be perfect fitting, but will work. The white covers I find at Do It Center hardware franchises, they are holding up well. I avoid the clear plastic greenhouses, I find those covers are very tight and tend to rip easily.
Don’t leave the covers on year round if you can help it. The UV damage will eat at the covers and cut the life down on them quickly. If it snows, and you have them up, be sure to go out and knock the snow off gently. Reduce the weight on the roof.
I use them along with my greenhouse, for overflow (we grow a lot of starts) and have the potting table next to them for ease of use. This year we set up an actual grow station, and put it inside a large dog run that was given to us, to keep the chickens, dogs and deer out of. Having it all nicely together, it makes my work more time efficient but also keeps it warmer, with it being dense, it blocks more wind.
I shuffled things around this year till I liked it.
I need to buy a replacement cover for one of the pop ups.
Having a tidy area to work in also gets you more likely to get to work.
Potting table ready to go.
Now then. If you build a portable greenhouse the frame won’t blow away. But once you put the cover on, it becomes a kite. You must keep it held down. Each brand/version that is sold will have different ways to tie down. Some have 4 (or more) points to attach rope to, to then connect to stakes. These in theory work, but if it is windy (and this island when is it not windy?) will either rip out of the ground, or rip out on the cover. Instead, here is what we do:
After building the frame, you can wrap duct tape around the metal pieces where they connect to the plastic connectors, if your frame has that. Some newer styles are fully built and are a pop up tent. However, these styles don’t have built in shelving.
Zip tie the shelves onto the frames. This gives stability in wind storms so your pots don’t fall off. As well, always put your pots on 1020 trays so they are not bouncing on those (always) unlevel shelves.
For best wind protection, have your greenhouse back up to a fence or building. Fences work well as you can connect to them.
If against a fence, and your cover has D rings or fabric loops, use zip ties to connect to the fencing up high. I lash the lower frames to the fences as well using long zip ties (or connect a couple together to make it longer). This holds down the back side efficiently. If against a building, it will be harder to do this. You can use the included rope to stake out the back however.
The biggest thing you can do is weigh out the bottom of the frame. We use paver bricks to do this. They are flat and heavy. We use 4 per greenhouse. 2 per side. I suggest using 12″ versus 16″ size, so you are not tripping over them as you putter inside.
You can see both sizes are used and the 16″ overhangs quite a bit. You can also see a white zip tie in the corner, around the frame, where it connects to the fence behind.
Another option if you have extra wood laying around, is to make a frame, and then using the U shaped brackets, screw it down into the frame. That will add a lot of stability.
Some of the covers will have overhang at the bottom, a skirt if you will. These you can place rocks or bricks on, to help hold it down. If it has it, use it. The white covers I am using now don’t.
The last thing though, that ensures dealing with winds? ZIP THE COVER TIGHTLY. I know. It is crazy, but don’t leave your greenhouse open at night. Only during the day, to regulate the temperature inside. As soon as the sun starts dipping I go zip up. Often you won’t need to vent the greenhouse until end of March and on. By May as I get ready to plant the covers come off to harden the plants (just snip the zip ties on the cover and pull off). Each day, when you open up the greenhouse and roll the door up, take the time to check the Velcro tabs around the frame are still together. Some covers will have ties instead, and these hold better over time. The Velcro will slowly loosen over time, so redo periodically.