To Burn, Or Not To Burn...

[silken]

I grow my orchids in a greenhouse that is attached to our house. It has a triple glazed clear poly carbonate roof and fairly large western windows. It also has 3 south facing windows on the short wall but the neighboring house shades the sun pretty much there. In winter there is snow on the roof more often than not and I supplement with T5 lights. In spring thru fall we cover the entire roof with a shade cloth. I forget what % of protection but it is a green mesh one and is likely around 50%. This year for various reasons (long story) we have not put the shade cloth on yet and I am cringing for my orchids. I have hung a few outside but 90% of them are in the greenhouse. Many of the Cattleyas and Dens are exposed to the worse sun and glare you can imagine. We have always said we're sure that the roof magnifies the sun more than just being outside. You almost need sunglasses to be out there. I have increased the humidity and am looking into getting a swamp cooler. In the meantime I have also installed a mist line from the roof that goes on for a few mins 4 times a day. It doesn't wet the plants much, just helps cool. Nothing is showing any sign of burning so far so I doubt that they will now. For the Milts and Masdies, they are out there too but I have a thin fabric over their stand and a fogger running as of recently. I also have a mist wand that creates a fine cloud of mist several times a day in their direction. So far so good and it gets to 90 degrees in there. They do get a cool quite humid break every night thank goodness.

I'm not saying this is a good thing to do, but mentioned it to illustrate how much sun some of these orchids can take. I am curious to see if I will get more or less blooms in the following months.

[MJSK]

Quite an interesting discussion. About month ago, I gradually introduced a Den. nobile hybrid, a Den. kingianum and a Schomburgkia lueddemanii to the sun. Last week in Boston it got incredibly hot. The leaves on the Schomb. got bleached out, the Den. kingianum hot a few bleached spots on some of its leaves and the Den. nobile's leaves turned a bit yellowish. I left the Schomb. where it was because it seemed so damaged, the Den. kingianum I moved to a slightly shadier spot and I moved the Den. nobile into my 'sun room' greenhouse where it gets afternoon sun, filtered through the glass, but it gets sun from above which is better than a window sill. These are relatively new plants, the Schomb has never bloomed. I am interested to see if the Dendrobiums bloom again for me.

Bud, it is amazing that you are able to grow orchids around tall buildings in New York City.

[RJSquirrel]

sunburn injury results when plant tissue becomes dehydrated after being heated to a critical point by direct sunlight. keeping the plant properly hydrated will go a long way in avoiding sunburned leaves bulbs or canes. Of course if you cant keep up with the need for this then your plants are at risk and should be kept in a cooler location. Now all things considered if you cant keep up with the need for moisture then you have to reduce the light and then the plants dont grow as fast and possibly not bloom either. I convinced myself you dont need to burn your catts and reyleas to get nice blooms. I havent gotten any blooms yet but Im still convinced I can grow a nice foliaged catt that blooms out without burning the leaves as I see too often done to them.

[isurus79]

Originally Posted by RJSquirrel

sunburn injury results when plant tissue becomes dehydrated after being heated to a critical point by direct sunlight. keeping the plant properly hydrated will go a long way in avoiding sunburned leaves bulbs or canes. Of course if you cant keep up with the need for this then your plants are at risk and should be kept in a cooler location. Now all things considered if you cant keep up with the need for moisture then you have to reduce the light and then the plants dont grow as fast and possibly not bloom either. I convinced myself you dont need to burn your catts and reyleas to get nice blooms. I havent gotten any blooms yet but Im still convinced I can grow a nice foliaged catt that blooms out without burning the leaves as I see too often done to them.

I definitely agree that burning leaves is a no no! But acclimating plants to higher levels of heat and light over a period of time is definitely acheivable. From my personal experience, I've seen much better results (in terms of growth and blooms) from plants that are given very high levels of light. I've also seen a lot of plants that do well in lower levels of light as well though. Orchids really are very adaptable!

[Trini Kjeldz]

i actually grow papilionanthe in 50% shade for months then give them 6 hrs direct light.....u wont believe the amount of flowers that bloom....ofc i live close to the equator my sun is deadly......but as for ur species....leaf burn is not necessary at ALL for good blooming......at ur latitude sun muchhhh lesss intense so try direct morning and protect at midday hrs and den allow direct light again after the hottest part of the day......mist directly before u do that and ensure humidity is always high