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What is the Best Greenhouse Plastic to Use?

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Shade cloth in greenhouse

No one wants to pay more than they need to, and you might be wondering if the plastic sheeting at the hardware store can be used for a cattle panel or poly tunnel greenhouse. I had the same question when I was planning my greenhouse, and I get asked this question a lot.


The quick answer is no, general-use plastic sheeting should not be used. Greenhouses should be covered with greenhouse plastic, as it's designed to stand up to sunlight and low temps. Other plastic sheeting will end up costing more and will be a ton more work.


Here’s why.


Greenhouse plastic is made with additives that provide UV protection so it can withstand the sun day after day. I used this 6 mil greenhouse plastic with UV-resistant materials that prolong the life of the plastic. It’s also designed to stand up to freezing temperatures. This means it won’t get brittle and crack. I’ve heard several stories from folks that used non-greenhouse plastic and it barely lasted a year out in the weather. In addition to the cost of replacing the plastic, it’s a lot of work to rip off the old plastic and attach a new sheet.

Thickness is important too, since it needs to stand up to heavy rain, snow, hail, and falling sticks (if it’s partially under a tree like mine). I recommend 6 mil rather than 4 mil.


What about the color of the plastic? Is clear, white, or green the best? Clear plastic lets the most light through and is the recommended choice for greenhouses. Some small greenhouse kits come with green plastic because green (and white) don’t let as much light and heat in. This can be important for a small 2’x3’ or 4’x’6 mini greenhouse that doesn’t have a lot of ventilation and can overheat very quickly. For larger greenhouses, shade cloth is used to help keep the greenhouse from overheating.


Now that we know which greenhouse plastic to use, let’s answer a few more common questions. You might still be wondering a few things like how long will it last, is it recyclable, how much will I need, or how is it attached, so let’s talk about those.


How long will it last? The manufacturer says the UV-resistant properties last for 4 years. I’ve read of several people keeping them for 5-6 years before replacing it. I’m heading into year 3 with mine, and will see what the condition is when it hits 4 years. It’s still in great condition other than the few holes I’ve patched due to falling sticks from the trees overhead.


Is it recyclable? I find conflicting information when I research this question. I recommend calling your local recycle center and asking if they take polyethylene plastic sheeting. You may also find some other uses for it in your house or garden once it’s no longer good for the greenhouse. It can be used to cover raised beds in early spring when there’s a threat of frost or heavy rain. It can be used as barriers and enclosures when spray painting or for containing dust when woodworking. It can be used as a tarp to collect and haul leaves in the Fall.


How much is needed to cover a greenhouse? For an 8’x12’ greenhouse, the minimum size should be about 24’x36’. This allows for plenty of room for it to extend down and onto the ground.


And finally, how is it attached to the greenhouse? When attaching the plastic to a wooden base, you can use a staple gun. A word of advice here; a few pieces of wood trim should be placed on top of the plastic once it’s stapled down. Without the trim, a strong wind will rip the plastic up from the staples. With trim, this isn’t an issue.


I hope this is helpful and answers some questions for you about greenhouse plastic!

 

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