Urgent Orchid Advice - Withering/Yellow Lower Leaves

[phalorchidto]

Hi OrchidBoard!

I've grown orchid flowers for awhile. My phalaenopsis orchid plants have gone from green leaves to yellow leaves within a few weeks and many leaves have dropped off of all the plants. The leaves turn yellow/light green and drop. The plants receive bright, indirect light and the upper leaves don't show light burn.

I water once every one/two weeks during the winter and every 9 days depending on the moisture in the pot. So, I removed the sphagnum moss from one pot and the bark media from the other pots which have many perforations for circulation.

Positives: There were no rotting or mushy roots to cut. All the roots are green and firm. No aphids/mealybugs/pests were found. I water the plants with distilled or rain water at 0 ppm.

Cons: The leaves continue to turn yellow and dozens have fallen off of the 6 orchids.

I appreciate any advice.

[Mountaineer370]

Welcome to the OB. I'm sorry you're having some troubles with your Phals. One thing I'm not totally clear on from your post: You say you've been growing orchids for a while. Do you have other orchids besides these Phals discussed here, and if so, how are they doing? One of your pictures says it was taken in July. Is that when these Phals were acquired, roughly eight or so weeks ago?

Another photo shows a new leaf on one of the plants that appears to be brownish. A growing, healthy Phal will sometimes shed a lower leaf or two, but what I'm seeing in your photos and what you describe does seem abnormal.

Also, you've described the light conditions and watering regimen. What about your temperatures? Are you using fertilizer? I apologize for all the questions, but I think a little more information would help our members come up with some ideas and suggestions.

[rbarata]

The new leaf colour might indicate too much light.
Does that plant gives you pink flowers?

[phalorchidto]

Thank you for the replies Mountaineer370 and Rbarata.

Also, several light/medium-green leaves dropped following the yellow leaves.

@Mountaineer370: I grew dendrobium nobile-type orchids and oncidiums before but only phals at the moment. I acquired the plants in July and the temperatures are around 68F/20C.

I use dilute fertilizer every other week. Also, the yellow leaf color only occurs in the lowest leaves and the upper leaves are dark green. It can't be shedding as 5-6 leaves have dropped from each plant. Maybe it is humidity or temperature, as the air indoors is somewhat dry?

@rbarata: The phal had a purple leaf when it was acquired and the flower color is either purple or yellow-white.

[Mountaineer370]

Hmm, if your temperature is around 68F all the time, I'm thinking that's cooler than Phals like to be. I grow only Phals because that has ended up to be the genus that seems to do the best in my conditions. My house is in the lower 70s in the daytime and may drop down to 68 or so at night.

There are others here who are far more knowledgeable than I, and hopefully, they will be along shortly.

[Mountaineer370]

Bumping this for our new member here. Anybody have any other ideas?

[rbarata]

68 F is acceptable for most phals, except some more demanding species.

[aliceinwl]

Were the leaves dropping before you removed the substrate and what kind of substrate did you switch to? If you’re leaving them bare root in the pots, they’re going to need a daily soak.

I’ve had some Phals drop leaves when going from moss to bark or when water stressed for an extended period. The light is also shifting with the changing seasons, I’ve had to shuffle some of my Phals in the last couple of weeks to prevent burning, but I think I was too slow on the uptake and a couple will drop some of their older leaves as a result.