Burlap, sheets, shade cloth, lace…what can you use? What should you use?
Let’s simplify this so that you and your plants and animals stay happy and healthy!
The most important thing to consider will be the density of the fabric. This is the term for how loosely or tightly the fabric is woven - and therefore how much sun shines through. Yes, color and type of fabric play a little role, but are secondary considerations in my opinion.
Spoiler alert! 50% shade cloth that is knitted (vs woven) is the simple answer that will be a fine solution for quite a few plants and greenhouse locations.
Of course, we’ll go ahead and dive in deep and consider all aspects, but know that 50% shade is good for many plants.
The trick to knowing which shade cloth to buy is simply to know how much sun your plants need. Are you growing tomatoes, tropical houseplants, orchids, or herbs? You’ll want to choose shade cloth density based on what you want to grow.
You may be wondering if you need shade cloth if your greenhouse is already in shade or partial shade. Like the answer to many gardening questions, the answer is…it depends…and you may want to experiment. (My greenhouse is in partial shade and I use shade cloth. More on that below.)
The ultimate goal here is to control how much sun your greenhouse is getting, whether that’s by it’s location or by using shade cloth. And how much sun you want your greenhouse to get will depend on what you want to grow.
Shade from trees or a building will block light from reaching the plants. Shade cloth will filter sunlight to let a certain percentage through.
This brings us back to fabric density. This refers to how loosely or tightly the fabric threads are woven, which directly affects how much sun gets through. Products labeled as garden shade cloth are either knit or woven. Knit shade cloth is made from polyethylene and it has more loosely woven threads and it can be cut it to size without it unraveling. This means it’s more lightweight and easier to work with. Woven shade is made from polypropylene. Its threads are tightly woven together and it’s a bit heavier, but it offers more UV protection than knit shade cloth. It will unravel if it is cut or gets a hole.
Let’s talk about some other options. I use burlap in my greenhouse and a friend of mine uses large pieces of lace. Both of these are loosely woven and so they make a good shade option. Burlap is a natural material made from the jute plant. It can also be made from sisal, hemp, flax, or other fibers. Lace can be made from cotton or synthetic fibers.
Now that we’ve talked about thread density, let’s talk about what that means for shading our plants! Garden shade cloth will be labeled with a shade percentage such as 30% shade, 60% shade, and so on. Here’s a guide to optimal plant shade percentages:
Heat-loving fruits and vegetables such as tomatoes, cucumbers, and strawberries, generally need shade cloth that is around 30% shade, meaning that about 70% of the sunlight gets through to the plants
Many flowering plants and many fruits and vegetables generally like 40%-50% shade
Partial-sun vegetables and herbs such as lettuce, spinach, and cilantro do well in 60% shade
Shade loving plants like ferns, orchids, and philodendrons like 60%-90% shade
People and animals will be the most comfortable in 80%-90% shade
Burlap isn’t labeled with a shade percentage of course, but it’s about 50% and creates a beautifully natural look. I’m going to guess that lace is about 30%-50%, depending on the lace pattern and if pieces are layered and overlap each other. Thrifted lace from garage sales and second-hand shops can be one of the cheapest options and has huge cottage charm appeal!
I’ve seen some folks use pretty sheets as garden shade. Since sheets are made of tightly woven fabric, I’d have to guess that the shade percentage is pretty high. I probably wouldn’t use them unless I’m growing shade-loving plants. Even then, it might turn out to be too much shade.
As I mentioned above, my greenhouse is located in partial shade and I use shade cloth. The back half of my 8’x12’ greenhouse is under very tall oak and maple trees. The front half gets more sun although it still gets a little shade from surrounding trees. Even though it gets natural shade, it still heats up to 100 degrees on hot days when it’s in the path of the sun. It definitely feels better inside with shade cloth! Plus, I use my greenhouse as a sanctuary to putter about and hang out in. It’s important to me that it’s comfortable. I don’t try to grow fruits and vegetables; those are in my raised beds in the garden.
I decided to use burlap because I love the airy charm it lends the greenhouse and because it was inexpensive. Believe it or not, when draped across the header beam and down the sides, it has a billowy, elegant look. It easily clips on to the metal cattle panel sides, and I can roll it up if I want to. As of this writing, I’ve been using it for two years, and I love it.
Now, back to some other considerations when choosing shade cloth. You might be wondering if dark colors or light colors are better.
Here’s the scoop. But first, it’s important to remember (you’ll see why in just a minute) that if you’re using greenhouse plastic on your greenhouse, it protects from UV rays.
White shade cloth reflects sunlight and heat. It keeps a greenhouse cooler, but it only diffuses light and so lets the full light spectrum in, including harmful UV rays. You might want light shade cloth if you live in a hot climate and you’re constantly trying to protect your plants from too much sun and heat.
Black shade cloth absorbs sunlight and heat. It makes a greenhouse hotter, but It filters light and offers protection against harmful UV rays. You might want dark shade cloth if you live in a cooler climate and want to keep as much heat in as possible. Or you might want dark shade cloth if you’re using it out in the garden without the protection of greenhouse plastic; as an added benefit, it will blend in to the landscape better than white shade cloth.
Are the differences significant or negligible? It’s hard to say. It will depend on your climate, your goals, and your aesthetic preferences. For me, black shade cloth wouldn’t help me much in the winter because my greenhouse doesn’t get much sun during that time of the year (it’s on the north side of my house and I live in a cloudy area). In addition, I don’t try to grow during the winter, so I’m only concerned about the other seasons.
This post wouldn’t be complete if I didn’t mention one other idea. And that is to place the shade cloth over the top of the greenhouse, on the exterior. The benefit is that the cloth absorbs or reflects the light and heat before they even enter the greenhouse. Again, is it significant or is it negligible? I haven’t done it so I can’t say. But some folks do place it on the outside and then fasten it down.
If all this information has got you feeling a little heady, just remember this: shade cloth in a greenhouse is usually necessary, and many, many plants do just fine with 40%-50%. If your greenhouse is dedicated to growing something specialized then you may want to consider a different option, but for many of us this will be a good solution.
And don’t forget about other little tweaks you can do in the greenhouse. Move light-sensitive plants under a table or behind a larger plant. Place shade cloth on the sides and leave the top unshaded. Or shade one side and leave the other side unshaded. The more time you spend out there, the more in-tune you'll be with where the sun is hitting and what plants need shaded. Observe, and your plants will tell you what they need.
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