Yellow Leaves

[jayman8117]

Novice here, new to the Orchid Board.
I saw a yellow leaf, and it turned yellow quickly on a Burr. Stefan Isler "Lava Flow". I removed the leaf.

also, I see a leaf getting yellow from the tip of the leaf on a blooming Bulbophylim echinolabium X sulawsii

day time temp is in the high 60's because plants are in my office, and we like the AC on high. I leave an open window to bring a breeze, and some coolness at night, when the AC shuts off, am I doing this right?

by the way, the office window is West North West., the plants are 10-15 feet from window. I had them on a table next to the window, and then I read they don't like direct sun, so I moved them.

What's going on, please help. I don't want to lose them.

[RosieC]

Hi Jay and welcome to Orchid Board.

A pic of the 'chid would help, but here are my first thoughts...

AC is probably not good for most chids. It dries the air a lot and humidity is probably too low. Also cold drafts from the AC may not be good, Orchids like air movement but most don't like cold drafts.

I've searched online about this chid. I've not found info on the same one but the link below gives care info for Burrageara Nelly Isler 'Swiss Beauty' and I would guess it could be similar.

Orchid of the Week Library: Burrageara Nelly Isler 'Swiss Beauty' AM/AOS

According to that high 60s will be right on the lower end of the required daytime temps, it would really prefer to be warmer. Also Humidity should be over 50% and I would bet the AC is making it lower than that.

Leaves can yellow in different ways, so a pic may help us to understand what is happening.

[King_of_orchid_growing:)]

The Bulbo hybrid you have will not like it too much when the temperatures are that consistently low.

Both Bulb echinolabium and Bulb sulawesii are intermediate to warm growing. Day time temperatures should ideally be between the mid to high 70's F and 90 F. Night time temperatures can be as low 55 F to 65 F. There needs to be a significant temperature difference between day and night in order for them to initiate a spike. Humidity should ideally be around 60% to 70%. Bright shade to shade is fine for lighting. Do not allow Bulbos to go bone dry. They should only dry out to the point where the media is damp, then water again. Bulbos love good air circulation, but not from a direct fan or AC breeze.

[King_of_orchid_growing:)]

Bulb sulawesii has the species name sulawesii for a reason...

They're originally from a place in Indonesia called Sulawesi.

Indonesian mid to highlands have pretty mild climates.

[camille1585]

Where was the leaf the Burr lost? If it was on an older growth and was one of the outer leaves, it could be natural leaf loss. Or it may be due to the AC and low humidity as was mentioned above. Also, 15 feet away from a window is like putting the plants in total darkness, since the amount of light recieved at that distance is negligable even though it may seem bright to us. How much direct sun does that window get? While they don't like full sun all day, Oncidium intergeneric do appreciate a few hours of sun in the morning or late afternoon. If you have more sun than that, just pulling them a few feet away from the window is enough to avoid full sun yet get bright light. Or you diffuse the light with a sheer curtain.

[jayman8117]

Camille 1585
thanks so much. it is an outside leaf. also, there is new growth, some new leaves growing.
I have a money plant next to the orchids, and the leaves move from circulation from the open window nearest the orchids.
Also, i do have a tray(a long flower pot),w here i have gravel and keep water to near the top of the gravel, for humidity.