Help! my orchids were burnt in my new greenhouse!

[SMS]

I have been nurturing along a small group of plants that I had atop a bookshelf in my kitchen with some direct and diffuse western light through a window, plus some limited sun through the southern window. All plants seemed to be happy, but I wanted a better set up for them, so I bought a small portable greenhouse. However, the greenhouse is 70" tall, and the non-orchid lover I'm married to (!) declared it too big for the kitchen, so I moved it to my deck. I live in Oakland, CA, where it has been warmish this summer, lately day time temps ranging from 68-85, barely cooling off now and probably somewhat mild for at least another month. The Greenhouse door area ( vented open) faces southward , while the sides face east and west.

After a few days most of the plants were not having a resort experience! The phals are pretty much OK ( except hat one has a small whitish patch on one leaf), and my small cataleya is fine. But, my 3 paphs look awful. Two older, larger ones ( late fall and early spring blooms originally) have blackened or brown leaves, and /or dark spotting on leaves. One paph has a black patch that has made the leaf almost translucent, so that you can see veins on the leaf. Another has two leaves with large black patches that yellowed and appeared to produce smaller patches that look almost moldy. The smallest one has one brown spots on one leaf.

So, questions:

For the paphs with the darkened leaves ( esp the "moldy like one) can I just cut off the outer most severely damaged leaves?

Any other immediate care ( insecticide, other treatment for these leaves?

And, regarding relocating the greenhouse, I could move it downstairs, which would be beneath the deck, so the light would be a bit less harsh and I have an eastern facing wall that could block one side. I also have a large basement, which gets cold in the winter, and has limited light. But, I do not have the time to work on lights etc right now.

Thanks,

Shelley

[chemist]

Hi Shelley,
First question: do you have good air circulation in your greenhouse? From your description sounds like you don't. Put an oscilating fan first (non oscillating will do the job too I think at least for now), otherwise nothing else will help. Even though one side is open it might be not enough to circulate air inside if there is no wind blowing toward greenhouse door.
You dont have insects so you don't have to use insecticides, but something to get rid of mold and fungus. Probably physan 20 will work. More experienced growers might suggest something else.
Good luck!

[78Terp]

Svetlana is right. Air movement is critical on a number of levels. Cooling the plants is one of the reasons. I had a fan blowing on my outdoor growing orchids this summer. I had a couple of friends kind of laugh at me, but I don't care. The fan helped keep the damage from outside sunlight to a minimum.

Also, the air movement helps keep disease at bay.

Can you post pictures of the damaged orchids? Pics are the best way to get good advice on the steps needed.

[Jx3]

Paphs and an unobstructed southern exposure. ... ouch! How about some kind of shade cloth for your mini greenhouse?

[SMS]

thanks for the input. I'm thinking of moving the greenhouse downstairs so that it will be below the deck ,, keep the western side vented open and adding a fan. If I do that and put shade cloth ( best kind? how much/thick?) on the southern facing side, does that sound like it might work? My paphs were a bit burned, one has a bit of ribbing, and one lost a leaf, but they are actually persevering. The catelya lost one tiny leaf, but otherwise seems OK. The Phals , however, are in terrible shape. My healthiest, most roust phal lost almost every leaf. ( repot?) Another has 3 moldy ish leaves, while the third and fourth still seem alive. Attaching photos, would appreciate comments.












Thanks,

[raybark]

There is nothing you can-, or should do with the burned tissue. As the still-living cellular structure is intact and protected by the burned tissue, there is no potential for infection. In time, those areas will become brittle and parchment-like, and you ought to be able to break off most of it, leaving a "fringe" of dead tissue on the living part.

I haven't looked into the physics of it, but for some reason, plants seem to perceive the glazing of a greenhouse to be the apparent source of the light. A plant that is 3' from the glazing might burn, while one 6' away will not - obviously it's not the difference in distance from the sun that's the cause, as that's only 3 feet out of 491040000000!

[kdennis14]

Thank you Ray,