Roots dying - am I not watering enough?

[flyfishdoc]

I have an Oncidium Sweet Sugar that I repotted last month. I don't recall any root problems when I repotted. I changed to CHC, perlite and charcoal from whatever it came in from the dealer (bought last year from good seller). Today when I watered, I saw rotten roots. I am watering once a week, with rain water. Feeding 3 out of 4 weeks (weak). There are 2 new growths (seen on the right). The humidity even on the humidity tray gets to 35-40% a lot of the time now. Most of my other orchids have drying air roots, so I doubt over watering or staying moist. I switched my phals to a mix with some sphagnum moss to keep them from drying out.

My inclination is to water more often until it gets warmer and the heat goes off (next month I should see 70s and humidity and can open the windows)

Jerry

[Ross]

I would not increase watering yet. It's rather common for older roots on backbulbs to brown up, especially right after transplanting. New roots will emerge from the newest bulbs and new growth, when the plant gets ready. You could try to induce rooting with one of the hormone compounds like Superthrive or KLN. Additional watering will only speed up root decay at this point.

[King_of_orchid_growing:)]

Is your humidity through out the entire room 35% - 40% or is it just the humidity tray?

[flyfishdoc]

Unfortunately the whole room (and house) has low humidity also. It may be 1 or 2% less

[King_of_orchid_growing:)]

Well then, I think humidity is the problem.

You may need to increase the humidity. If the air around the humidity tray is 35% - 40%, it's still pretty low. A humidity of around 60% - 70% would be better or if that's too difficult, try to shoot for at least 50%.

I also suggest the next time you repot, to find a way to do it in an area that's not so dry or maybe wet the roots. If the air around the room has humidity as low as 1%, it may have put your plant(s) into shock.

[Ross]

I grow mine in lower humidity (30-40%) and do not have this same problem. My Paphs and Phals and Masdies all grow well under lower humidity.

[flyfishdoc]

Everything else is doing well. This humidity level has been the same all winter. I have 2 phals that bloomed a month ago. Some of the air roots are dry, others have stayed green. I have a potinaria that has 4 blooms that just popped out of the leaf cover, and I have a 3 foot spike on a McIra. Yellow Star 'Okika' that grew 3/4 of an inch a day until this week

[Tommyr]

Get a humidifier. I use a Air O Swiss 2 gallon model.