actually looks like sun burn

Georgetoo,

The damage looks like sunburn to me. Why do think it is not sunburn? Outside in Mexico would seem to be a good place to burn phals. I burned some phals when I pulled off my shadecloth in December and I'm about a 100 miles south of Chicago.

Mike

I have seen similar -- sunburn.

Reflected sunlight can also be a cause of fried plant tissue. A friend of mine has referred to an occasional orchid being "lasered".

--Stitz--

I think it might be a combination of sunburn and not enough water. You can loose leaves due to them not having enough moisture to maintain cellular tissue. What do your roots look like? Are you watering before it gets totally dry?

Looks like a classic case of sunburn to me also. Could there be an open area in the tree where the sun manages to get through just to these few plants at a critical time of day?

I ruled out sunburn because these are plants grown under shade cloth. I water them all once a week and of the 175 or so phals in the collection only 7 or 8 have been thus affected. Most are in small lava rock. The phal pictured is still in bloom and I will repot as it is lifting and check the roots when the flowers are done.

Have to keep an eye out for that laser.
Pictures are of my front growing area, due north on right hand of both pictures.

Here is a link that might be useful: Carport growing area

I vote sunburn. Maybe there's some sort of reflection coming off your shade cloth?

Beautiful plants, love those dens.

Jane

Georgetoo,

I took a look at the photo's of your growing area. Is there a chance that the light in the morning or afternoon shines directly on the phals, even for just a few minutes? Also, I use 80% shadecloth on my phals and they seem to get enough light to grow well and flower. I believe that high light intensity damages the leaf by raising the surface temperature of the leaf beyond its limits and that high ambient temperature and low humidity contribute to the problem. If you had WAY too much light, you would be seeing it on all of your plants, but if you're on the edge, the damage would likely be limited to just a few. When I remove my shade in the winter, I usually get a burned leaf or two and it seems like it is usually a broad new leaf with its surface at 90 degrees to the early afternoon sun. Somestimes it's several from the same gross, while others in the immediate vacinity, but with different parentage, are as happy as can be. The last time this happened was with a venosa cross.

Mike

Well ok everyone....sunburn.

Have to observe a little better and find out the source. I have 70% shade but it has that opaque fiberglass above it. We have a rainy season from Jun-Oct and it is necessary to control watering.

Jane....I'm a late comer to dens but I think you get more bang for the buck out of them when they are in bloom. Unfortunately not many available down here.

I love your carport growing area, your orchids are lovely and so healthy looking. Love the ones that are growing,
up to the roof. They are really reaching to the sky. Tricia

Sunburn. Hands down. I have one that I know I burnt a leaf on, still sitting in my kitchen. It looks IDENTICAL.