shade cloth question for cattleya orchidss

[clay576]

Hi,

I am in Houston and my patio receives about 4 hours of intense afternoon sun, shaded in morning though unfortunately. I had 40 percent cloth over all my cattleyas but I'm noticing there's some sunburn showing up. Does sunburn show up immediately or does it take a couple days? Also, I recenlty just added another layer of the 40 shade cloth. What percentage of coverage do I now have? I realize this is probably a simple math equation but I'm not sure how to calculate it. I realize it's not 40+40 = 80%. Anyway, thanks for any help.

Clay

[Miller]

I am considering putting shade cloth over my orchids on my deck as well. The arbor covering gives them dapple lighting mid day but some orchids still received some damage on their leaves. I too am in Houston and the morning light is great on my deck but there is a bit of afternoon sun that creeps in between my arbor covering and the neighbors trees. How do you have your shade cloth setup? Would you be willing to post some pictures?

Thanks,
Miller

[Halloamey]

The calculation part is easy, as you thought 40+40 is not equal to 80 in this case.
Consider there are 100 photons of light coming from the source of light to your plants.
Now you have a 40% shadecloth, that means it allows 60% of the light to pass
Therefore 60% of the 100 photons = 60 photons pass the shadecloth
Now you have another layer of 40% shadecloth, it allows 60% of the 60 photons to pass through it
Therefore 60% of 60 photons = 36 photons pass through finally to your plants
That is finally your double layer of shadecloth allowed 36 of the 100 photons through i.e. 64% shade.

[Halloamey]

Hi,

I am in Houston and my patio receives about 4 hours of intense afternoon sun, shaded in morning though unfortunately. I had 40 percent cloth over all my cattleyas but I'm noticing there's some sunburn showing up. Does sunburn show up immediately or does it take a couple days?
Clay

Sun burn can show up immediately or can take a couple of days depending on the temperatures, humidity and air movement around the leaves. You can look up some recent posts about similar questions, one nice link would be from the AOS about the right light, here it is

AOS Beginners Newsletter

If your conditions are a bit drier and there is less air movement I would recommend the filtered light conditions illustrated in the article, but if you can provide enough humidity (>60%) and good air movement then bright light as illustrated in the article will benefit the Catts.

[clay576]

perfect! ok then
I did the calculation right. Down here in Houston, apparently I need that much shade for afternoon full sun. Does this sound right? I thought 40 percent, one layer, would be enough, but not so since they started sunburning. Thanks for the help.

[tucker85]

40% shade should actually be pretty good for most cattleyas. But if they aren't used to it, they'll burn. They'll usually show signs of burning within 24 hours. If you want to use that shadecloth, put the orchids out there for an hour a day, for a couple of days and slowly increase the time. You can mist the leaves to keep them from burning also.

[Kmac]

I just put up shadecloth for my catts. I debated between 50% and 60%, and finally settled on 60%, since Texas sun is pretty strong, and this spot will get sun most of the day. So far, all I know is that nothing is burning...too early to be sure its enough light, but it seems pretty bright. Well see. Let us know how yours does.