Storm-Proof Your Plastic Greenhouse: 5 Ways To Make Sure It Stays Standing Strong

Plastic greenhouses are great for extending your growing season but have gained a reputation for collapsing or blowing away in winter weather — and in some cases only lasting a single growing season. However it doesn’t need to be this way!

Simple re-enforcement to the base using garden pegs, upgrading the supplied guy ropes to ones suitable for all-weather camping, reorienting the plastic greenhouse away from prevailing winds, pinning the frame down to the ground with weights or lumber, and staying on-top of maintenance can all ensure that your plastic greenhouse lasts for several years.

In this article (and in the video below), I’ll walk you through some of the top tips submitted by hundreds of gardeners explaining how they secure their greenhouses. And I’ll show you what I do to make sure that my plastic greenhouse stays standing strong all year round.

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1. Reinforce the Frame

Perhaps the most common and demoralising issue that owners of plastic greenhouses face is them collapsing in strong winds due to the relatively loose fit between the metal poles and the plastic connectors.

But there are a few quick steps that you can take to stop the frame from collapsing in the night and from having to spend the morning rescuing all of your seedlings.

Connect the Roof to the Base

When Storm Isha came rolling through, it blew so strongly here that the plastic cover that wraps around the outside of the greenhouse, tried to tear off the top half of the metal frame and it partially came away from the base. The base itself was firmly fixed in place and unmoved – and I’ll explain why in a moment – but the roof was simply pulled out of place because it was only held down by a tiny amount of friction and gravity. But we can do better and stop this from happening!

To stop the roof from being torn off, you should add an additional connection from the top cross beam directly to the base of the structure using a rope or a bungee cord, as shown in the photo below. That way you have an external tension holding the frame together rather than just relying on the small amount of internal friction created by the contact with the plastic connectors.

You should also add additional bungee cords across the sides of the structure, ideally diagonally from near the top and down to the bottom corner, to both prevent any large-scale twisting motion and to prevent the poles at sides from popping out of the frame.

If you do this on all sides of the greenhouse, you should have added enough extra rigidity that the structure that could, in principle, be rolled around your garden without it breaking. Keep tightening the ropes until the poles can’t be gently pulled out by hand. Since Storm Isha, we’ve only had Storm Kathleen and it didn’t cause any damage but I’ll let you know here if it ever falls down again.

Use Cable Ties to Secure the Shelves

In my plastic greenhouse, the shelving is just a set of wire racks that are loosely placed on metal poles on the inside of the frame. A stray swing from your hips or even a tug from getting caught on your jeans can be enough to completely destroy a tray of seedlings, let alone a storm.

To make sure that the wire racks don’t go anywhere and that your plants have somewhere solid to grow, use small cable ties or zip ties to attach the racks to the frame. Not only will this prevent your shelves individually collapsing but it also adds additional rigidity to the overall structure and stops the bottom half from collapsing.

Use Glue if You Don’t Plan On Moving Your Greenhouse

When I reviewed my plastic greenhouse last year, I was left with hundreds of comments from viewers about how they secure their greenhouses. And one of the simplest and easiest ways of creating an unbreakable structure was to add plumber’s glue on the inside of the plastic connectors during the build to secure the metal to the plastic.

To me, this seems a fairly weather-proof way of making sure that the structure cannot fall apart.

It also has the added advantage of ensuring a water-tight seal around the edge of the metal poles which should prevent any possible rusting on the exposed edges of the pole or even inside the poles – which are hollow and uncoated. This should mean that your plastic greenhouse lasts much much longer.

2. Secure the Plastic Greenhouse to the Ground

The cornerstone of protecting any plastic greenhouse from wind damage is ensuring that it stays firmly fixed to the ground. There are many ways you can do this and my viewers left a lot of great suggestions but I think I’ve stumbled on the cheapest, easiest and lowest-profile way of making sure that your greenhouse doesn’t budge in high winds.

Use Garden Staples to Peg the Greenhouse to the Ground

Applying garden staples* around the base is the simplest and easiest option if your plastic greenhouse is positioned on grass or earth. Take two garden staples for every metal pole that touches the ground and use a mallet to peg it in at each end.

On my greenhouse there are 22 poles around the base and that means it took 44 pegs – although you could skip the short poles under the shelves and use fewer in the centre if you’re running short. You can buy them relatively cheaply on Amazon and after applying them, you can leave them alone and there’s almost no maintenance.

I’ve not touched mine in two years and the greenhouse hasn’t moved even slightly. The second greenhouse I purchased was damaged by Storm Isha and the top came off completely but the base didn’t budge at all and helped keep much of the upper part standing.

If you were to do one thing to improve your plastic greenhouse, let it be this. It’s a ten minute job that will help you plastic greenhouse stand strong for years.

Weigh Down the Frame With Anything and Everything

Many viewers said they added weights on top of the poles in the centre of the greenhouse to help weigh it down. That way, when there were high winds, they simply weren’t strong enough to lift the extra weight.

Popular items were bags of compost, paving slabs, breeze blocks and bricks. If you’ve got the materials lying around and need to store them somewhere, maybe try storing them on the base of your plastic greenhouse. Although be aware that slugs may enjoy hiding underneath them.

Use Ground Anchors to Strap or Bolt the Plastic Greenhouse Down

Other viewers suggested using more extreme DIY solutions for securing the frame to the ground. One suggested using ground anchors, digging them into solid ground, and strapping the whole greenhouse, cover and all, firmly to the ground. While others suggested mounting the frame on wood and attaching the frame to it with pipe clips. Some people went further and buried the wood in a trench.

3. Stop the Plastic Cover Blowing Away & Tearing Down the Greenhouse

Once you’ve reinforced the frame and ensured it’s pinned to the ground, there is little that can go wrong if you make sure that the wind doesn’t get inside or damage the external plastic cover. This cover is hard to replace – you usually need to buy an entire greenhouse, poles and all – and once it’s damaged, it’s hard to repair. So let’s make sure it never gets damaged in the first place by taking the following precautions.

Replace the Guy Ropes and Ground Pegs

Get rid of them. The ones that come with the greenhouse are useless. They’ll give you a false sense of security which makes the damage even more devastating. Throw them in the trash asap.

The supplied ropes don’t lock in place very well – there isn’t enough friction or tension to be able to do so. And that means that the ropes just come undone in the wind as it slowly makes the cover tug on and loosen the ropes. Once the ropes are loose, you have no protection and the cover will flap whenever the wind blows and that will cause the fabric ties on the inside of the cover (that connect to the metal frame) to break. Once the fabric ties are broken, your cover will fly off and be gone forever and, if you do find the cover, they are difficult if not impossible to reattach. Small rips will also start to appear where the fabric ties have come off and they will get bigger over time, making your plastic cover pretty useless pretty quickly.

So the best thing you can do is to throw away those ropes and buy a new set that is designed to hold tents up in high wind. You basically want to buy some high quality camping gear.

I use these guy ropes* because they were well priced at the time and had good reviews and were a lovely green colour but any guy rope set with good reviews will do. You’ll need 4 ropes as there are four loops on the cover – one on each corner – but you can always double up (which is what I did).

And to connect the ropes to the ground, I just use the same garden pegs* that I used to secure the frame in place – one per rope – but you can always use tent pegs. After the garden pegs, I think this is the second most effective thing you can do to improve the lifespan of your plastic greenhouse. Don’t skip it!

Use a Bungee or a Strap Over the Top of the Cover

I’ve not tried this myself but a few viewers wrote in to say that they use straps going over the entire structure, including the cover, and tie it down to either the base of the frame or to nearby breeze blocks or other weights or anchors on the ground next to the greenhouse. Apparently the cover doesn’t budge even slightly, even in high winds and even with the door open.

While this will definitely work and completely limit movement and therefore any stresses on the frame and the fabric ties and prolong the life of the cover, I think you can avoid this step if you can make sure that the wind doesn’t get inside the structure.

4. Maintain the Plastic Cover to Stop Wind Getting In

Plastic deteriorates under ultraviolet light. There’s no way of getting around that. It’s also easily damaged by sharp objects and, from time-to-time, you might start to notice signs of damage on your greenhouse cover, especially following extreme conditions.

When you see signs of damage, you should act straight away to minimise the extent of the problem.

Patch Up Any Holes

If you spy a hole in the cover, then you should use duct tape or gorilla tape to patch it up as soon as possible. If you don’t, the wind will start to get in which will create further stress on the cover and potentially exacerbate the damage (depending on it’s location). If the hole continues to get too large, the wind will get inside and start to shake both the frame and your seedlings.

Patching up holes is straight-forward. Clean off any dirt, wait for it to dry and then apply the tape to cover over the area, being sure to use several pieces to fully cover the hole and adhere to a large area of the nearby cover. If you apply the tape from bottom to top, the patch-up will last slightly longer as less water will get in through the seams. And be sure to patch up the same area on the inside too so that the adhesion to the cover and the seal is even stronger. For any holes that form on the corners of the cover, patching both the outside and inside will limit movement and prevent further damage.

I use gaffer/duct tape*, but some of my viewers prefer all-weather Gorilla Tape*.

Consider Removing the Cover Over Winter

If you don’t plan on using your greenhouse during the coldest, darkest and windiest part of the year, then the easiest way of prolonging the life of a plastic greenhouse is to remove the plastic cover over winter and store it indoors or in a shed.

I find my greenhouse frame didn’t suffer any rust damage without it’s cover but some viewers have managed to make their greenhouse last several years by completely dismantling their plastic greenhouse when it isn’t in use.

Make Sure Wind Can’t Get in Under the Flaps

Around the base of the greenhouse are plastic flaps, sometimes referred to as an overhang. This isn’t normally attached to anything and while it does provide additional airflow, it also allows a lot of wind to get in. Be sure to either pass the flaps under the frame and tape them to the inside of the cover and then to lightly mound earth around the base of the greenhouse, or weigh down the flaps with heavy weights.

Many viewers have used items like stone, bricks, wood and breeze blocks to weigh down the flaps and I find grow bags a very practical option which, when full of plants, can hide some of the plastic and make the whole setup much more visually attractive too.

With the frame fully solid and secured to the ground, with the cover strapped on tight, and now able to keep the wind out, your greenhouse should last a lot longer. However there is one more thing that you should do to make your plastic greenhouse last as long as possible…

5. Position Your Plastic Greenhouse Away From the Wind to Limit Damage

With the door open, your greenhouse cover acts as a giant sail, picking up the wind and trying to fly away. This is what causes of most of the damage. In the winter you can leave the door shut when it’s windy but, in the spring and summer, when there is more sun and higher temperatures, some airflow is required to stop temperatures rising to the high 30’s or even 40’C/104 F and damaging your plants.

The best way of positioning your greenhouse to limit wind damage is so that the smallest side or one of the corners furthest from the door is facing the prevailing wind. That way the wind can simply deflect around the edge of the cover, without imparting much force on the greenhouse.

In the UK the prevailing wind is usually from the Atlantic in the South West but it will depend on the shape of the landscape in and leading up to your garden. By having the door facing North East you can reduce much of the wind damage – just be sure to keep an eye on the forecast and to close the door when the wind turns!

You should also take steps to prevent the temperature inside the plastic greenhouse from getting too high in the summer, including placing the greenhouse in a sheltered position. Conveniently, this can also help reduce wind damage, particularly so in the UK, where the prevailing south westerly happens to coincide with the position of the sun during the warmest part of the day.

Are Plastic Greenhouses Really Worth It?

With a little bit of modification, I think these plastic greenhouses are a really cost effective way of extending your growing season and providing a dedicated space for growing plants – I did buy two of them, after all! You can find out why I think they are so good in my review article below.

Many viewers also agreed that they are great starter greenhouses, despite some of the above issues. And while they can’t beat the quality expensive glass and metal greenhouses, they can beat poly-carbonate greenhouses after making these upgrades and they beat all of them on flexibility. They are also great for renters like me and that’s why, if space allows, I might even get a third.

Happy Gardening!

Are Plastic Greenhouses Any Good?