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Reflective sunlight

Posted by lowraine North Carolina (My Page) on
Mon, May 25, 09 at 9:00

Now that I determined that I have about 6 hours of sunlight I would like to increase the amount with reflective light. My sfg space in within a space that is made up of railroad ties that bring the space up off the original yard. The north side of the sfg comes up to the railroad ties so I have a large maybe 8" tie that I can use to place something that can reflect the sun from that side. I would like some thoughts of what some of you think would be a good material to use and if you think I am only spinning my wheels. I will try and give you a pic of the garden if I can figure it out. I guess I also need help in sending a pic.


Follow-Up Postings:

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RE: Reflective sunlight

Hi, ^hours of sun is actuallt probally enough, however if you want more try alluminum foil. mirros may las longer but they will most likey cook your plants. another thing to consider is that extra reflected sunlight probally won't increase the length of time light hits your garden but rather will increase the intensity of that light . the mor intense light may do more harm then good. Another option would be to paint the ties white which may be a better option then covering them with alluminum foil.


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RE: Reflective sunlight

I would go with something white rather than something reflective.

To post a pic, upload your photo to a site like Picasa, click on the "link photo" button then copy/paste the embedded photo info into your post.

Here is a link that might be useful: Tales of a Transplanted Gardener


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RE: Reflective sunlight

Thanks for the thoughts, I think I will take the wait and see for the moment. Maybe I will have enough sunlight. Better to do no harm and wait and see. I will go with white if I decide to do anything. Thanks again.


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RE: Reflective sunlight

As long as the light is only being reflected and not magnified or concentrated, you shouldn't be burning your plants. Mirrors will only reflect light so you should be o.k. if you went that route. To test this theory, take a magnifying glass, a mirror, and a piece of paper outside. Reflect the light from the mirror onto the paper and nothing happens. Now, use the magnifying glass to pass light through to the paper and it will burn easily. If you had multiple mirrors all focusing on the same point of your garden, it would heat up enough to damage your garden.
Mirrors big enough to reflect light onto your garden sounds expensive though.


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RE: Reflective sunlight

I was just researching this, and I'm thinking about trying a mylar blanket. They're pretty cheap. I did a quick search and found one that's 84" x 52" for $1.66. I haven't even tried ebay yet. I just finished arranging some straw bales for my garden, and realized one part only gets partial sunlight for almost the whole day. So I'm considering my options. And I'm also wondering if I could set some up to direct enough light through my windows to grow some tomatoes indoors. I'm thinking a good sized reflector could really brighten up a shady area. But you'd probably have to be careful not to add too much light to the sunny parts of your garden.


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RE: Reflective sunlight

How about planting things that require less sunlight?


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RE: Reflective sunlight

Mylar blankets are a poor choice as they can concentrate light and burn tissue. This is why foil is a bad idea in coldframes in winter.

Reflected light is lower light quality than direct sunlight and is a suboptimal solution to seeking more light or planting crops that need less light.

Dan


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RE: Reflective sunlight

Dan,

If the reflector is flat, how will it concentrate the light? Wouldn't the reflected parallel rays remain parallel, and maintain the same intensity, minus what didn't get reflected? Or is there something about the mylar, or foil for that matter, that I'm not aware of? I'm pretty new to this, and I've never used a cold frame. But I can see how foil would keep light and heat from being absorbed by the walls. And if there wasn't enough ventilation, it could cook what's inside. I'm planning to use that idea to build a dehydrator. But out in the open, I can't see how you'd have that problem.

I know the other option is planting stuff that likes shade. But sometimes you really want more space for something that needs direct sunlight. Anyone know a type of heirloom tomato that likes dappled sunlight? I'm planning to rotate tomatoes into that area next year, so I thought I'd try one plant near that space this year to see how it does.

Dan


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RE: Reflective sunlight

Tomatoes need at least 6hrs of 'direct sunlight' to do well. You can grow them in indirect light no doubt, just not well.

The right plant for the right spot. That's how mother nature does it ;-)


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RE: Reflective sunlight

Dan,

you can't get Mylar flat, and one doesn't need to bring reflected light to a focus to find reflection is problematic. My coldframe has foil only on the south wall for a reason, from experience. Greenhouse growers don't put mirrors or foil in their greenhouses for a reason.

Dan


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RE: Reflective sunlight

Dan,

I don't doubt that mylar or foil is a problem in an enclosed space like a cold frame or greenhouse. Just like a car in the sun with the windows rolled up, where the heat gets trapped. But that's not the same thing as being out in the open. If the mylar happened to be shaped so it was concentrating the light, that might be a problem. I dunno, maybe there's some other reason it's a bad idea. I can't say for sure, because I've never tried it. Do you know of anyone who's tried it in an open area? And what the results were?

Dan


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RE: Reflective sunlight

First, dope growers use Mylar inside, so we know it works. The issue here is that too close and you get burning,, as the manufacturers themselves say (thinking about on top of soil). .

Second, AIUI above, there is a need to increase the light due to the prevalence of shade in the area. Reflecting poor-quality light still gives poor-quality light. Unless there is a system of mirrors pointed throughout the yard., Mylar is not going to increase the light quality. So why bother? White paint is cheaper and less obtrusive.

Brighter light is not the same as better light quality. It takes direct solar radiation to start photosynthesis. Bright indirect light merely delays the metabolic processes that start, among other things, dark respiration.

Bottom line: waste of money in this instance.

Dan


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RE: Reflective sunlight

Dan,

I read that mylar has about 97% reflectivity, which is more than white paint. So unless it absorbs certain important wavelengths--I'm assuming it doesn't--then the reflected light shouldn't be any worse than it's source. And it's cheap. But--and maybe this is what you've been getting at--if a plant is getting a certain amount of light in a shady spot, and 97% of direct sunlight is added to that, then maybe it's getting way too much now, instead of not enough. Is that the problem? And if you set up the mylar to reflect from a spot that isn't directly pointed at the sun--possibly missing wavelengths important to plants--is that the low quality light you're talking about? I'm thinking it would be more blueish like the sky, instead of whatever color the sun is. So a different mix of wavelengths. If that's what you've been trying to say, then I can see why white paint could be a better idea outside. In my case, I can't really paint anything--I'm renting, and I can't paint the garage--so it would be easier just to hang something reflective up in a sunny spot. But if that ends up being too much light, I guess I'd be better off trying something else.

Also, when you mentioned "on top of the soil", did you mean it's a problem if light is reflected up, so it hits the leaves from underneath? That would make sense, since plants have evolved to grow in stuff that doesn't reflect like a mirror. But I'm just guessing on that.

Even if I don't try mylar outside, I may still try it inside. I'm thinking I could use smaller grow lights, and save on electricity that way. Hey, if it works for the pot growers... :)

Anyway, thanks for your insight. You sound like you've been doing this a lot longer than me.

Dan


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RE: Reflective sunlight

If mylar works inside (i.e. dope growers - who seem to have no growth problems) then why can't it work outside as well, especially if we were to use a series of mylar panels to capture sunlight from say the rooftop of an urban home and reflect that light onto perhaps 2 other mylar panels or dome shaped frames (perhaps facing the dome angle outward not inward like a pocket)??


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RE: Reflective sunlight

Because the light is different.

Dan


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RE: Reflective sunlight

Do a search for Daily Light Integral and the type of plant you want to grow. Skip the stuff about Mylar, white paint and such.

Mike


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RE: Reflective sunlight

Hi lowraine,

I realize that it has been ~ 4 years since your posting, but this is something you might want to double-check: railroad ties are said to be toxic and I was told that they pollute soil around them ( by releasing whatever stuff they were treated with when manufactured). So, maybe you would consider getting rid of them (and possibly of the soil they have contaminated)... Take care!


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RE: Reflective sunlight

Bring this post back from the dead. This is maybe the pretties way to use mirrors yet- a picket fence, where the pickets are mirrors. I haven't tried it yet, but for even a south facing patio, it would be hard to burn plants with this, as far north as I am. I may try a mock up of mylar strips.

Here is a link that might be useful: Picket fence of mirrors


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