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If you’ve been dreaming of a greenhouse, you’d be at an advantage to learn what a greenhouse is and how it works. Your research will most likely bring you to this issue of UV rays, which is a hotly contested one in the greenhouse community- UV rays. So, do greenhouses block UV rays?Do you want to block UV rays?
While this issue of whether or not to block UV rays is contentious, it is true that certain greenhouse materials will block certain kinds of UV light. For example, greenhouse glass blocks 96% of UV-B radiation while only blocking 25-35% of UV-A.
So, why is blocking UV light important? Should you get material with high UV-blocking capacity? Why does the issue matter? This article will discuss everything you need to know about greenhouses and UV rays and why the issue is such a hotly debated one in the greenhouse-building community.
The Main Question- Do Greenhouses Block UV Rays?
While we’d like to simply state a yes or no answer for our readers, the question really isn’t so easy to answer. Whether or not and how much UV will be blocked by a greenhouse depends not on the presence or absence of a greenhouse but on the materials it is made of.
Not every gardener wants to block UV rays in his or her greenhouse, and therefore, greenhouse material industries have learned to cater to the variance of opinions on UV blocking.
For example, depending on the material you may be considering, you’ll likely find a differing range of UV-blocking capacity. According to Greenhouse Product News, your standard greenhouse glass blocks different UV rays at different percentages.
While we’ll go over the difference between UV-A and UV-B radiation later in the article, it’s not important for now. The point is to remember that different greenhouse glasses will block different percentages of these rays. For example, you may find two greenhouse glass plates, one with 25-96 UV-A to UV-B blockage and another with 35-90.
What percent of each ray to block will vary depending on opinion. Some gardeners believe that allowing the full spectrum of light into their greenhouses will better mimic natural conditions, just with a greenhouse’s added advantages. Others believe in minimizing damage to plants and greenhouse equipment.
So, when we’re asking whether or not greenhouses block UV light, we’re really asking what materials a greenhouse is made of.
It gets even more complicated when you consider options like shade cloth (Amazon link). According to Greenhouse Hunt, shade cloth can be used to minimize UV rays in seasons where such rays are in over-abundance.
We won’t even talk about the decreasing UV-blockage that occurs when UV rays damage a greenhouse’s roof and walls. That’s another topic for another day, involving lots of maths and sciences, which we as simple gardeners aren’t quite qualified to discuss. It all just goes to show you- the question is a complicated one.
So, why the differences in opinion on UV rays? Are UV rays somehow harmful? We know how damaging they can be to human skin, but can they hurt your plants, considering the fact that they’ve evolved to sit in full sun all day, every day? In the next section, we’ll discuss some of the differences in opinion on UV radiation and whether it belongs in a greenhouse or not.
Why Do Different Gardeners Choose to Block Different Amounts of UV Light?
In the greenhouse gardening world, the topic of UV radiation is far from decided. Some gardeners choose to block lots of UV light, some very little, and some as little as humanly possible. So, why such a divide on UV light?
The fundamental origin of this divide stems from the paradox of UV light: it is a potent and damaging form of radiation, and at the same time, it’s part of a plant’s natural environment. A gardener’s goals and personal preferences will vary widely, and thus the amount of UV light a greenhouse blocks will differ as well.
Some gardeners, whose tactics involve complicated contraptions- the Rube-Goldbergs of the greenhouse world- dislike UV rays for their corrosive properties.
UV rays are a very potent form of radiation, with the potential to damage everything from greenhouse plastic to internal wiring.
These kinds of gardeners, the kinds who build greenhouses for which one turn of a lever can water whole rows of plants, aren’t content to go around each plant by hand. They want big contraptions, complicated wiring, and convoluted tubing.
To keep all of this going, they have to do a lot of maintenance work. Part of that maintenance work is protecting their equipment from damaging UV rays, which have the potential to derail an entire system of pipes, nobs, and sprinklers.
For these gardeners, a greenhouse is about efficiency and innovation- and they’re willing to sacrifice the allure of a more ‘natural’ growing environment to make sure their plants are watered evenly, and that nursing plants is an intuitive and straightforward task. In a sense, they pay for convenience and efficiency in the chance to give their plants a more natural surrounding.
Other gardeners like to keep things au natural. For these gardeners, a greenhouse is just a way to keep their plants protected from destructive elements in the atmosphere- like, for example, frosts and windy thunderstorms.
These gardeners may be more focused on providing conditions that mimic a perpetual summer day. Part of the advantage of a greenhouse is that its walls will insulate your plants from thunderstorms, frosts, and even too much heat if you tune them up right.
So, you can see why some folks prefer not to pay attention to UV or take efforts to allow UV radiation into their greenhouse environment. The philosophy here is that if the plants can take it, they must need it. Plants have evolved thousands of years to live in the environments they currently call home, and those environments include UV rays.
But are they right in assuming that everything natural is good? Can UV rays actually harm your plants or stunt their growth?
Can UV Rays Harm Plants?
The question of harm to plants done by UV rays all revolves around one question: what kinds of UV rays are we talking about?
With regard to UV-A, you don’t have much to worry about. You’ll notice that even the high-blockage greenhouse materials we mentioned at the beginning of the article don’t concern themselves so much with blocking UV-A.
UV-B rays, on the other hand…
According to a NASA-affiliated website, overexposure to UV-B rays can impair photosynthetic activity in plants, hindering their ability to create the energy they need to survive.
This results in less plant growth, which will result in a smaller-than-desired yield for gardeners with bigger goals. You can see why some gardeners might want to block out UV-B rays in this case.
However, the jury is far from out on the UV-B issue. According to another study, UV-B, in conjunction with UV-A, can actually help stimulate photosynthesis. This would result in the exact opposite outcome from what was suggested in the NASA article- greater growth and greater yields. So what’s up- why all the difference in opinion?
One has to remember that the sciences are a touchy field. What’s discovered one day may be contradicted the next day, and what’s considered cutting-edge research today may be history tomorrow.
That’s not to say that the sciences aren’t valuable. If you’re looking to get the best possible yields out of your plants and your greenhouse, you’d be at an advantage to study horticulture. The sciences are full of helpful little facts that can help you optimize your yields and build the best possible garden.
It’s just to say that there are no definite answers. If you want to get the best yields, take suggestions and do as the scientists do- experiment. Do what you love most and grow- the results from your experiments will teach you which ways work best for you.
So- Yes to UV?
Since this article is all about whether or not a greenhouse will block UV rays, it would make sense to talk about whether or not you want it to.
Yes, and no. If you’re letting your plants receive the full battery of the light spectrum, and you’re getting tiny yields and pitiful growth, then you might try a UV-blocking material or a shade cloth.
On the flip side of that coin, you may want to try a more permissive solution with UV rays if your greenhouse is a high-tech space-age masterpiece, but you’re still not getting higher yields. Play around with your UV-blockage. Become a mini scientist. Have fun, just as you always do when you’re in the garden.
All in All
All in all, the question of whether greenhouses will block UV rays is a complicated one. On the one hand, yes, they could, but that depends on whether or not you build them with UV-blocking in mind. On the other, you could undoubtedly make a UV-permitting greenhouse if that’s what you think works.