Oncidiums in trouble

[OrchidsSweden]

I've had these Oncidiums for about 8 months now, they were never doing great but they keep trying. The Twinkle is trying to grow a new pseudobulb, but at the same time many leaves have been yellowing and falling off. The older pseudobulbs that recently completely lost their leaves are now drying up and dying off as well.

Do you think anything can be done for the poor guy, or is it doomed to fail? The new growth does look healthy so far and it is growing new roots, but I'm not sure it will be enough to save the orchid.

I only have two Oncidiums and both of them are struggling. The other one (I don't have an ID for it) is all shrivelled up and while it attempted to grow a pseudobulb it appears to have given up on it. It has stopped growing.

Both Oncidiums were delivered to me in the same pot as an arrangement, I thought with some attention they would recover.

What to do? I'd be grateful for any help and tips. Also I've got photos from when they were in bloom if anyone wants to try to ID the mystery orchid. Thanks!

[Roberta]

First, Welcome!

The new growth is key... keep it happy and the plant will thrive, it's natural to "feed" from the old pseudobulbs to grow the new one. That's also the source of new roots. The medium looks much too coarse for Oncidiums, which like to stay damp. Two major causes of desiccation of the older pseudobulbs - not enough water, or bad roots (so that the plant can't utilize water). A suggestion would be to unpot it and see what is happening with the roots - if new ones from the new growth, just increase frequency of watering, and ideally get a more water-retentive medium (smaller bark, or sphagnum) If there aren't good roots, the challenge is to keep the humidity up around the plant (like maybe plastic bag over it) to keep it from further desiccating while it is working on a new root system.

[estación seca]

Welcome to the Orchid Board!

These are plants that like water and shouldn't dry out. Yours have been kept too dry. I don't think medium to large bark is good for Oncidiums except in a very wet growing environment.

I agree with the suggestion to check the roots. I would repot into sphagnum moss kept moist but not soggy wet. Use a much smaller pot just big enough to hold the plant. Raise the humidity around them any way you can - bag, terrarium, jar. They are amazingly tough plants so they certainly can survive.

With central heating spider mites often attack Oncidium leaves. I don't see them in the photos but you should watch for them.

[Leafmite]

The other way you could go is to pot in lava rock and soak once a day. Doing this is more work but will provide more humidity to help those thin leaves from losing so much moisture. It will also prevent the roots from rotting.

Those of us that live in places that become cold during winter often have trouble with humidity during the winter. The pseudobulb stores extra water for the plant and when leaves lose more water than the roots can absorb for the plant, the pseudobulb is forced to supply the water to keep the plant alive...until there is no more water to supply.

If you can keep the new pseudobulb alive, the plant will recover. If these ones die, I hope you will try again. Good luck!

[OrchidsSweden]

Thanks for all the advice! I've repotted them in sphagnum moss with a top layer of bark/leca. Hopefully they will recover. Oncidium is a new area for me and I haven't seen them in flower shops here in Sweden before or since. Fingers crossed, replacing them won't be easy unless you turn to nurseries.

On the photo you can see the arrangement as it was when I bought it, minus the condition of the pseudobulbs. I guess I was too focused on the flowers...

[OrchidsSweden]

Unfortunately the 'Twinkle' issues continue...

Now it seems the new pseudobulb is rotting away (see photo).

Does anyone have any suggestions?

[estación seca]

It's a difficult situation. The commonest causes of new Oncidium growths dying are not enough water or excessive temperatures. I doubt your temperatures are too high.

New roots only form on new growth. The plant needs to make new growth to survive. The older pseudobulbs may still hace enough strength to make another growth.

I would suggest keeping the medium moist but not wet. Raise the humidity if possible with an enclosure. Keep in bright light but not direct sun. Hope for a new growth, but it may not happen.

[OrchidsSweden]

My indoor temperature ranges from around 21C (69,8F) to 23,5C (74,3F) with humidity levels usually around 40%. It can go up to 60% on more humid days when I keep the balcony door open. Maybe the moss absorbed too much water?

Also, I finally managed to find another Twinkle from a nursery, yay!

If this one dies, which I suspect it will no matter what I do at this point, I'll have a back-up. Its fragrance is what won me over... so I simply have to try again with this one. Maybe Oncidiums don't do well in my climate, I'm not sure.

Other species grow well for me, I put all my orchids on a shelf with artificial light. The Oncidiums are the only ones that don't seem to appreciate it all that much so far. The challenge is on... Although the loss of an orchid is kind of a big deal for me, I haven't lost one since I got a sick phal in 2018. It immediately dropped its flowers and wilted away within a week or two, it went fast.

[Gardening in WM]

you know what they say, overwatering is the fastest way to kill an orchid.
The ideal water to air ratio for orchids is 50:50

Moss holds 16 times its own weight in water.

Ironically you were encouraged to overwater it which is a shame but I'm glad you have found a new one.

The only reason I have struggled with oncidium twinkles was from pests, otherwise they are one of the easiest beginner orchids.

Unfortunately orchids bought from flower shops very often contain pests that can catch any inexperienced orchid grower off guard, they will suck all the moisture out of the orchid and make it dry out. Otherwise healthy orchids can go months without water and still survive.

It's a learning experience for everyone.

[estación seca]

Your temperatures should be fine for Oncidiums.

The plant was in bark in the first photo, already looking like this. Oncidiums don't do well going months without watering.