Rust color on Vanda leaves.
 

All of my different species of orchids are developing brown (rust) color on the leaves. May I ask what is causing this? Thank you.

pictures pls

Also, what are your growing conditions? Temperature day/night? Humidity? What kind of light? Which genera of orchids?

Hello: Thank you to those that responded before I posted a picture. My orchids are developing this reddish, rust, brown color on the leaves. Seem healthy otherwise. I have them in a green house here in the Sonoran Desert. The green house is heated but I had trouble keeping it above 50 degrees during the coldest time this winter. High is set to 85. I have misters that I turn on manually a few times a day. I sure would like to know what I am doing wrong.

From the photo, that looks like the "suntan" that orchids get when they are at the upper end of the light range that they want (especially pronounce on those that have red or purple flowers) - no harm at all. It could also be reacting to the cold, depending on the specific parentage. Do you have a name for that plant? I would suspect cold is not a problem if that Phalaenopsis next to to it is OK. (The Vanda is a lot more cold-tolerant than the Phal, a few hours of 50 deg F shouldn't hurt it if it warms up during the day) It's important that the plants be dry at night when the temperatures drop - best to water in the morning, so everything dries out by evening. As for light, you may want to have some shade cloth handy to put over the greenhouse as the sun gets higher and more intense. (I have toasted plenty of orchids in March when the sun starts to clear obstacles such as houses and the light increases suddenly)

Thank you Roberta. I forgot to mention that I do have a 70% black shade screen over the entire green house. At this time of the year, the green house gets a lot of shade from a large shade tree to its south. I think that I will experiment then and move plants around to a shadier part of the green house. In summer, the green house will get full sun. Thanks again.

The Phalaeonpsis will definitely benefit with more shade. The Vanda can take higher light - that "suntan point" of light is actually ideal to encourage blooming. (Dark green leaves may be attractive, but insufficient light - indicated by dark leaves - is the primary cause of non-blooming in an otherwise healthy orchid) With any orchid, higher light can be fine as long as it is increased gradually - it is sudden change that toasts leaves. I can't read the tag in your photo... what is that Vanda? (it's species or hybrid name can tell a lot about cold-tolerance and light requirement)

I trust that you can read the labels now. These are obviously very young. I am a newby and just getting started trying to do the right thing with the orchids. I moved my Phals to the shadier side of the green house. The vandas have a lot of discoloration on the leaves not light green that I see on internet photos. Thanks again.

They are, indeed, babies. They would be happier a little warmer at night but I think they'll be OK. For such small plants, a heat mat would help keep them cozy on cold nights. Do keep an eye on light intensity... these are high-light plants, but in your location it is so bright that especially with seedlings you may want to give them a bit more shade.

I can bring them in the house for a month or so until the weather heats up some. Thank a lot for your advise.