Are Plastic Greenhouses Any Good?
Plastic greenhouses are a great way of extending your growing season and creating a safe environment to stop seedlings from going leggy and even growing plants from tropical climates. But are they really worth it for home-growers?
Plastic greenhouses provide an affordable alternative to glass but they have a reputation for collapsing and not keeping out frost at night. However they are a cost effective and flexible way of increasing your growing space that can outperform more costly options such as poly-carbonate greenhouses.
What they lose in strength and insulation, they make up for in flexibility: being suitable for almost all surfaces, very easy to transport while built and disassembled, and being quick to take apart and rebuild as needed, making them a great option for renters and beginners.
In this article, I’ll review my experience with plastic greenhouses and highlight the positives and negative experiences that come with owning one and outline some key upgrades that you need to make to improve the experience ten-fold. And I’ll draw on comments left by hundreds of viewers on a review video I made last year which you can watch here or below.
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What’s In The Box & Assembly
I bought this greenhouse on Amazon* and it comes with all of the poles and plastic connectors used to build the frame, a plastic cover to go over the top and wire racks used to create the shelves inside the structure. It also comes with some less than ideal instructions on how to put it together…
But after spending an hour or two assembling the frame, once you’ve figured out how to get the cover on over the top and attach it with the fabric ties, used the ropes to secure the cover to the ground like a giant tent, and you’ve placed the wire racks on the interior poles to create some shelving, you should be ready to get growing.
But that’s where the problems begin….
The Ropes Don’t Hold Fast In Mild Winds
The supplied guy ropes aren’t good ropes – there isn’t enough friction to hold the metal clips in place so you can’t adjust the tension like you can with normal (functional) guy ropes. I suspect the problem is the material itself being entirely polymer, rather than a blend with other fibres. Therefore it only takes a slight blow and the ropes that are meant to secure the cover, simply come undone.
But worse than that, the pegs don’t peg very well either! They bend really easily and don’t firm into the soil at all. Which means under strong winds, the pegs just come out of the ground so your ropes detach entirely – leaving your plastic cover to fend for itself and fight off the winds using nothing more than a handful of fabric ties knotted around the metal frame. When the wind blows and gets inside via the flaps around the base, it puffs out the plastic cover and shakes the frame – and that’s how seedlings end up spilling over the floor.
So the first thing you should do is replace the guy ropes and ground pegs to secure your cover to the ground. Use ones designed for camping and they’ll last for years without needing to adjust them. I use these ropes* and I use regular garden staples* as my ground pegs. I also recommend taking the garden staples and pegging the frame down to the ground using a mallet – I used two pegs per pole and my plastic greenhouse hasn’t budged in two years now.
The rest of this review is written assuming that you make these (sadly) necessary upgrades.
Common Failure Points
Despite making the above improvements, there are a few more common failure points of these plastic greenhouses that you should be aware of.
Zips
Okay, you only paid £60-80 for this item but to me it’s terrible that zips breaking is such a common problem. I own two plastic greenhouses and so far two zip tags have split in half, making it hard to open the door single-handed. One set of zip teeth managed to unpair themselves and while I did manage to rejoin them, it has caused some minor damage to the plastic cover. The other zip is okay though….
It’s not a deal-breaker at this price but be ready to do some DIY repair and to have to reattach the zips to the teeth or to the plastic.
Fabric Ties
If you rely on the supplied guy ropes and ground pegs or leave the door open during a storm, you’ll put a lot of stress on the fabric ties that hold the cover onto the frame of the plastic greenhouse. And you’ll find that it doesn’t take too many gusts to start to cause the fabric ties to tear away from the cover.
Unfortunately, you only get eight (one in each corner and two at the base by the door) and once they are gone, they are gone… You might also find that holes begin to form in the cover where the fabric ties were previously connected.
You can prevent this by limiting wind damage using the above precautions or making the DIY improvements in this article, but if you do see holes you’ll need to patch them up with tape to stop them getting bigger and allowing progressively more wind into the greenhouse, causing further damage.
Cover
The plastic cover isn’t made of strong stuff. It’ll survive you stretching it or trying to twist it but it’s very easily pierced by sharp objects and, like most plastics, will degrade under ultraviolet light – which is a significant problem for a greenhouse.
I’ve not experienced it myself but some viewers have noticed small perforations in the ceiling of the cover after one or two seasons. While I find that if trays are pressed against the inside of the cover, you can quite easily cause small holes to form in the wind as it rubs against hard items.
These small holes don’t cause structural issues like the holes around the fabric ties can because of how the cover is stitched together. And while holes in the ceiling might be beneficial in reducing heat build-up in the plastic greenhouse during the height of the summer, you do need to take care of your plastic cover or it will degrade and, unfortunately, you can’t just buy a replacement – you need to buy a new greenhouse.
Many viewers choose to remove their cover over winter and some even say that this act alone has allowed them to make their plastic greenhouse last for several years. I personally didn’t notice any rusting when one of my greenhouses was exposed to the elements during the winter of 2024.
Are Plastic Greenhouses Worth It?
For such a low price and given how much extra dedicated growing space it provides, I think plastic greenhouses are a steal – an unbeatable buy for the home-grower, especially for beginners.
They are easy to assemble, disassemble and transport to new locations. Even when fully built, you can carry it around the garden until you’ve found a position you like. And, perhaps controversially, the plastic cover flapping in the wind seems a more robust mechanism for absorbing the force from the wind than poly-carbonate greenhouses which are much more expensive and require a hard standing and yet they still collapse.
And if you make the upgrades outlined above and in more detail in this article here, then you can increase the lifespan of your plastic greenhouse and create a very safe space to grow young seedlings which doesn’t require cluttering your house with seed trays for months on end and provides the extra light that young plants need.
There is one drawback not due to manufacturing quality which is that there isn’t much airflow in there so, in the summer, it can get really hot in there and you’ll need to cover the top with a towel or shade cloth, but in the Spring it’s perfect.
Since buying a second plastic greenhouse* and making my upgrades I’ve not suffered a collapse, although the original greenhouse with holes in was less robust and requires a lot more maintenance.
If I had more space, I’d probably buy a third…
Happy Gardening!
