Yellowing from improper repotting?

[Joyce LaSorella]

Hi All,
I am new to this forum but have been growing orchids for quite a while. I appreciate any help I can get!
I repotted an Angranthes Grandalena almost two months ago because the medium seemed broken down. I used sphagnum moss in a clear pot with the expanded clay balls for drainage and except for one yellow leaf early on, all seemed well until the past week. Because I thought I was successful, I repotted other orchids this way... Now my Angranthes is yellowing quickly! The roots were abundant, pot-filling, really...what I can see through the clear pot still looks good. I am growing under lights and natural light in my living room, waiting for my greenhouse kit to arrive(!) Any ideas?

[estación seca]

Welcome to the Orchid Board!

What are your growing conditions? Temperatures day/night? Humidity? How are you watering? Has the light or temperature changed?

I'm not clear on how you potted it. Is the pot full of sphagnum mixed with LECA?

[Joyce LaSorella]

Hi! Since my plants are temporarily living in my living room, temp is high of 75F days and 67F lows, humidity 45-70% in the growing area. I water when the sphagnum is almost dry and the LECA in the bottom of the pot is dry, usually every 3 days. The sphagnum is not tightly packed. I thought I had uploaded a picture but I guess it did not work.
I use a Mars Hydro 1000w T5 LED grow lamp, along with some intermittent light from a shaded south-facing window. This plant's top leaves are approx 14 inches from the lamp and off to the outer region of the 3ft X 3ft grow area.
We have had some heavy winds that lowered the humidity to the 30s, then heavy smoke from wildfires--unsure if this could cause any problems, though.

[SouthPark]

Originally Posted by Joyce LaSorella

what I can see through the clear pot still looks good. I am growing under lights and natural light in my living room, waiting for my greenhouse kit to arrive(!) Any ideas?

The state of the internal regions of the pot and medium and roots will be important too. If for some reason the roots and media down in the depths are ultra wet and the water isn't moving much in that region, then that can create oxygen starvation issues.

Also, very wet and very cold roots is not a good combination. This doesn't mean that is the case for your orchid.

Abrupt yellowing of leaves can mean roots not operating normally ----- affected by something.

Sphagnum does indeed work well for some growers. It often requires finding a suitable watering strategy to avoid getting portions of roots too soggy/too wet for relatively long periods of time (for regular orchid roots).

Professional growers often use TIGHTLY --- or relatively firmly packed sphagnum ...... which can help with the 'wicking' of water. It is not at first intuitive ..... but can work well.

Some gentle air movement in the growing area also is beneficial (as well as having suitable growing temperatures).

[Joyce LaSorella]

Good information about sphagnum, potting firmly and finding that sweet spot with watering, temp and air movement. Thank you both. I don't seem to have this issue with the other plants I potted this way, but I hear that Angraecoids are sometimes touchy with repotting.

---------- Post added at 09:56 PM ---------- Previous post was at 09:41 PM ----------

I should add that all the other orchids that I repotted in the sphagnum with LECA at the bottom had clear pots with numerous small air holes and a large cone-shaped depression at the bottom to aid drainage.

[SouthPark]

Joyce ...... upload at any time later --- some pics of the yellowing etc. Upload the images at roughly 1024 x 768 pixels.

[estación seca]

If it went from higher temperatures or higher humidity to lower temperatures or lower humidity that could cause some loss of older leaves.

You mentioned the roots appear healthy.

[Ray]

You might also be seeing the impact of the change in medium.

As roots grow, they “tailor” themselves to function optimally in that environment, and once they have grown, they cannot change. Move them into a different medium and those existing roots are suboptimal for the new environment, so must be replaced by new roots.

[Leafmite]

I think the pictures will be very helpful. It is really difficult to diagnose this without seeing what is happening.

I worry that this might be a fungus issue. The Madagascar Angraecums seem especially prone to fungus issues (the island is breezy). The classic Angraecum symptom of a systemic fungius infection is the leaves turning yellow or black one by one (can happen within a few hours or weeks). If the roots were not kept dry and given a chance to heal after the re-pot, a wound might have provided an entry point for fungus. If you think that this is a possibility, a systemic fungicide would be the best option to try to stop this. The orchid can probably start new growth from the base if the main part of the plant is lost.

Good luck and I hope that this is not the issue. I looked up pictures of this cross and the result is absolutely gorgeous.

[Joyce LaSorella]

Hello,
Thank you for the information! I will try to post a picture--I thought I had uploaded 3 pics but can't find them...
I have Physan 20 if the cause is a systemic fungus (cringe!), but other explanations make sense as well. I will try the picture again.