Yes that's sun/heat burn for sure. You can even see the line where shade
from the upper leaf protected some of the tissue from burning. You can see
a less severe burn on adjacent leaves which are on the same plane in
relationship to the light source.

Temperature on a hot day can contribute to the burn; where on a cooler day
the same
amount of light would not burn them. Considering the temps outdoors in
Houston, I would guess a shading close to 60 to 75 % from normal noon day
light would be advisable.

for me "scorched" is the buzzword that brought to my mind the exact type of
damage your cattleya leaf shows.

"jtill" wrote in message
oups.com...

Al wrote:
in cattleya bumpy, raised, rough, discolored patches in the upper surface
epidermal tissue of a leaf show up in about 24 to 48 hours after a
"burn",
even longer in some cases. The mesophyll layer and underside of the leaf
may not be destroyed may continue to function. It usually but not always
shows up on tissue that is perpendicular to the angle of the light/heat
source. You may notice that sharp lines delineating burned and non
burned
tissue that seem to parallel the shadow cast by nearby leaves of other
things.

In contrast it is possible to burn the whole plant of a phal completely
"white" in just a few hours of direct sun at the right time of year here
in
Virginia.

It is harder to burn the same tissue if the light level/heat level is
increased slowly over several weeks, months and once the tissue has paled
because chlorophyll reduction. I often see sudden burning in the spring
since the increasing intensity of the sun gets ahead of my shade cloth
application.

There are other symptoms of 'burn' on different orchid's leaf tissue.
Under
the right conditions thin leaved oncidiums will burn flat and dead all
the
way through as even the mesophyll layer and lower epidermal tissue gets
destroyed by the heat/light.

There are many other ways to interpret your question depending on how I
think about the type of burn, and the light intensity and duration you
have
in mind. It can happen slowly or faster depending on all kinds of
variables. Got pictures for abpo?


"jtill" wrote in message
oups.com...
How quickly does sunburn show up? I seem to have scorched one CATT but
it's neighbors look fine. Just trying to push the light to far for
"Mother's Favorite" I guess.
Joe T
Burned in Baytown

This should show the scorched CATT although I am having startup
problems with this Blog.

http://joerex99z.blogspot.com/2006_0...z_archive.html

Joe T
Baytown