My Oncidium roots are molding, leaves turning yellow

[grasshopper]

In your original post you say that the orchids are potted in Hydroton in a net pot, which I can see in the pictures. To clarify, this is not the same as potting them in S/H. S/H allows for a reservoir of water to remain in the pot at all times to keep the medium moist. When you water in your current set up, it's really not that different than having potted them in bark...the only difference being the Hydroton won't break down like bark would.

Also, keep in mind that the areas of the medium that you can see will always be drier than the core (i.e., what's underneath what you're looking at). Onc's like to dry out some between each watering, so watering daily (even with Hydroton) might be considered overwatering.

To give you an idea of what I've done with a few catts: I have a few catts in regular clay pots potted in Hydroton and I water them as if they were in bark. This translates to 1-2x a week in the winter, 3-4x a week in the spring (it gets hot in Dallas very early) and almost daily in the summer when the temps really start to rise.

I am not an expert by any means, so maybe I'm missing something. Hopefully more people will chime in with advice.

Good luck!

[nutgirl]

I repot oncidium types into hydroton as a potting medium when I get them. I have found….
It usually takes a while for them to adapt to the change and the original roots eventually die off as new ones replace them (just because they look like they’re not growing doesn’t mean they’re not working). They seem to sulk for quite a while until enough new growths and roots develop.

I use clear plastic pots and even though the hydroton looks dry I can usually see condensation down inside. If you are using net pots you will have to water more frequently.

The outmost leaves on the existing ‘bulbs will turn yellow and drop off as the plant puts out new growths ( I see a new one in one of your pics.) They may also be reacting to the change in conditions.

Once the existing bulbs shrivel they usually don’t plump up all the way again. It’s OK, the new ones should be nice and plump
You plants look nice. You might send a pic of the whole plant.
　

Maureen

[Vanda lover]

If the plants were bare root, I would suggest cinnamon. I agree with the week Hydrogen peroxide. I know a man who adds a little to his watering can on a regular basis, ever since his daughter was cured of cancer by receiving injections of it.