Oncidium yellow leaves

[Lilarty]

I am relatively new to orchids and I am hoping to learn why individual leaves in this Sharry Baby are turning yellow.

[silken]

Can you give a little bit of history and your care info for this plant? How long have you had it, did you re-pot it, what kind of moisture and sun is it getting.

From the picture it appears to be potted in what looks like regular potting soil in a large pot. Oncidiums need a potting medium that can let some air to the roots and if potted in too large a pot, they will suffer from root rot since the pot takes too long to dry out. What kind of flowers are in the pot with the plant?

[tarev]

Various reasons for leaves to turn yellow. Could be over or underwatering..but Onc are water hogs, so it maybe underwatering.

What is your watering regimen and what kind of media did you use when you potted this plant. Have you checked the condition of the roots?

[Lilarty]

The plant is one my wife got at an orchid show about 3 weeks ago. It is still in the medium and pot we bought it in. There appears to be a layer of what looks like chunks of shellfish shells on top of the potting medium. There are no other flowers in the pot. I do suspect I was over watering it the first couple of weeks. I am considering repotting it so I know the condition of the roots and the real composition of the potting medium. I have gone to a weekly watering for it as of last week.

---------- Post added at 09:19 PM ---------- Previous post was at 09:14 PM ----------

Forgot to mention, the plant is in a West facing window with a 4 foot overhang above the window. My first orchid ( a Phal ) acquired last year bloomed there, if that is any indication of the light available there. I can move it to a window that gets more light.

[silken]

I would get a medium to fine potting media prepared and re-pot it. It's always a good idea to re-pot new purchases unless it is not a good time as in no new roots growing. I would be concerned about the condition of the roots on this. When you re-pot, place it in a pot with about an inch or less of room around it to allow for new growth. If you can tell where the new growth is coming from, you can place the old bulbs closer to the edge of the pot and only leave an inch of space on the new growth side. When they are in too big of pots they can get root rot too easily from always being too wet.

It can likely take more light than the Phal but should be done so gradually and not if it is stressed out with root problems.

[Lilarty]

I did re-pot it after the last response. The roots seemed very small. and would have fit in a 4 inch pot. It seemed to me that the roots were really undersized for the plant, and it had been in a 10 inch pot. Having said that It has now put out a spike. (in spite of my best efforts lol)

[RandomGemini]

No, the roots are not undersized for the plant. Sharry Baby has finer roots than other oncidium hybrids I've had experience with. I'm not sure why, but I think it's a feature of this particular hybrid. No need to worry about small roots. That's just normal.

Worry if you see brown or black roots that feel mushy to the touch. Healthy orchid roots are firm to the touch, white, silvery or green in color and sometimes yellow or white roots can be stained brown from tannins in the medium they've been planted in. The texture of the roots is key, IMO.

Are these yellowing leaves both on the same pseudobulb? If so, this is normal aging of the plant and isn't a problem. Oncidiums will drop leaves on their oldest psuedobulbs when they are done drawing all of the energy they can from them, so they can use that energy to grow new pseudobulbs, roots and leaves and hopefully, a spike.

If the pseudobulb is not also turning yellow, then I wouldn't worry too much about a yellowing leaf.