I just replaced all my south facing windows with low-e glass. I've been growing African violets successfully in these windows (with the shades down) for years, but now I'm wondering if the direct sunlight through the low-e glass will be too much for them. I'd rather not put up new shades if I don't have to, but I don't want to lose the violets.
effect of low-e glass on African violets
How much heat is coming thorough those windows? I have no clue about low e-glass but I would think as long as your AV's are a foot or so away from the window, they will be okay. I just don't think they would do well right up close to the glass reflecting that sun. Maybe you could buy an inexpensive AV and try it for a week and see what happens ... that way you wouldn't be subjecting your good plants to a possibly bad situation.
Thanks Plantladylin. The people who sold/installed the windows claim that the low-e glass reduces heat transmission by 75%, and I do notice a difference compared to the plain old insulated glass. Got no way to measure it, though. You would think the manufacturers/Professional Associations in the glass industry would have some data on this, but I haven't been able to find any. Some of these AV are 10-12 years old, and probably should be replaced anyway. Think I'll do a variation of your suggestion: take cuttings from every one of them and grow them in the greenhouse this winter, then just keep rotating the old plants as we've always done. If they crump, I'll have the answer...but I'll also have replacements if the older plants get too much light and pass on. Thanks again.
Never found anything official anywhere on the effect of Low-e glass on plant growth. But I've been growing my AV in full sun with no obvious ill effects since early November. They get 4-6 hours of direct sunlight through the windows every sunny day. Now I'm going to pull a plant from the GH that needs full sun to thrive and see how that fares...
Thanks for the update! Glad your plants are doing well. You're going to enjoy those new windows this summer... you can stay cool & still enjoy the view!
I can't add to the conversation but hope you have many avs thriving with your new glass!
Does anyone know if uv light is the cause of "sunburned" plants? The reason I ask is because my GH has twin wall glazing "with a uv filter coating". I have shade-loving plants growing happily side-by-side with known sun worshippers in the thing, and neither seem to be suffering. When I first built the GH, I used to "hide" all the shade lovers under benches, behind foam insulating boards, anything really, to protect them from direct sun. I haven't done that this year, plus I took down some trees to increase direct sunlight to 6 hours. Both shade lovers and sun worshippers seem to be gowing happilly. Now I've got AV/Dracaena/Pothos growing in basically full sun at the house behind this "low e glass", and they show no ill effects. So now I'm wondering if "foot candles" is the best measure for sunlight tolerance (what I always used), or would a "spectrum measure" be more useful? Help!
I imagine the manufacturers of low - e glass don't publish data that answers your question because there are too many variables to consider. For example, I have low -e coating on my east facing two-story windows, but still use supplementary lighting for my succulents and other light-loving plants because in the winter here in Connecticut there just isn't enough sun. We probably have similar low-e products, yet because my conditions are so different from yours we have very different results. With regard to foot candles vs. spectrum measure, that's a very interesting question. Here is a link to an article that is mostly about comparing the efficiencies of various light bulbs, but also has a detailed discussion of lux, lumens, PAR and a few other terms that have to do with how light is measured and how plants use light for photosynthesis. I don't know if it will answer your question about whether uv light causes plant sunburn, but I think you will find it interesting nonetheless. http://www.aquabotanic.com/lightcompare.htm Look for the article by Ivo Busco under lighting and equipment
You're right, wandygirl, that article didn't anwer the question---but it was absolutely fascinating! Thanks! Particularly the part about so many measures of light being related to the "human" perception of light. Plants aren't human last time I checked, so our common measures may be totally inadequate. Suspect the dearth of information of effect of low-e glass on plant growth simply means the work hasn't been done yet. Believe it would make a great thesis for a graduate student somewhere, so I plan to contact Clemson to explore it. There ARE many variables involved, but most are controllable. Simple split-plot design would do it. Thanks again! BTW, I used to live in Southbury back when it was a small, quaint NE town...I loved it back then...