Oncidium 'Tiger Crow' from grocery store
 

Hi everybody,
I'm very happy to get this plant back! I had one for almost one year but I managed to kill it. The plant was growing good but then I transplanted it and all roots died, old and new.
I have a lot of Dens and Cattleyas that grow wonderfully but with Oncidiums I'm cursed. But I would definitely like to learn!
What would you do with it?
Thanks,
Tango.

Beautiful!

What are your growing conditions? Day/night temperatures, summer and winter? Humidity? How much light? How are you watering? Are you using fertilizer? How often do you repot your plants? Is the entire pot full of sphagnum moss, or only part of it?

To generalize, I think in hot climates most Oncidiums that die do so from not enough water, and in cooler climates they die from old medium that breaks down and suffocates the roots. Scale or mealy bug insect attack, or spider mites, can also kill them.

Really nice flowers

Hi Estación Seca,

I have the plants in a bright SW-oriented, glass-covered terrace. Climate here in Málaga should be similar to San Francisco. I have 22-30°C in Summer and 17-24°C in winter, the air is normally moist (60%, even during daytime). I potted the Oncidiums into a mixture of perlite, bark and Seramis, and covered the top layer of the pot with sphagnum so the surface does not dry up so fast. I water the plants once a week, when the surface feels dry (the core is still wet, I have some wood sticks in the pots). The plants were almost for a year in their original substrate (coconut fiber), doing well. When they started to grow in June I transplanted them and since then, they started to decay. I already killed the old Tiger Crow and two nice Nelly Isler from my grocery store. I got a beautiful Goldiana from a friend and I also killed it. I have lots of Dendrobiums and some Cattleyas, and they thrive so nicely though... But I would not like to give up on Oncidiums.

What do you think?

Your medium is quite loose. Most of what you describe sounds correct. I suspect you did not water enough. The Oncidium group does not like to become completely dry. My growing area (with evaporative cooler) is usually 25-32C in summer and I must water Oncidiums every 2 days. In fresh open medium like you are using, in your conditions, I don't think it would be possible to overwater Oncidiums.

Edit: If they are making new growth without enough water, leaves develop transverse folds.

Hi again,
Wow thanks. Well this means I'm basically killing them by leaving them without water. Actually the new growths are somewhat folded...

What about transplanting? I hear all the time about people manipulating roots, cutting pseudobulbs, changing substrates... But I think Oncidiums are moody plants that like to be left in peace. What would you say?

Transplant orchids as they begin making new roots. For Oncidiums this is with new growths. I don't cut orchid roots. I take off medium that falls away easily but I don't meticulously remove old medium. Use whatever medium you like, but remember thet like lots of water.

So, common sense! Thanks!

I also agree that you likely aren't watering enough. Even here in somewhat northern Europe I water my Oncs 2 times a week in the summer and frequently leave some water in the saucers (not too much, just enough that the saucer in empty within 2 days or so). I use to kill every Onc I got until I realized that they need much more frequent watering than Phals!

Hey Camille,
Thanks for your feedback.
I guess I did not understand how different they are from the "dry" orchids.
I hope I can save my 4 remaining grocery store plants.
Best,
Tango.