Cattleya (Sophronitis) coccinea with yellowing leaves at the bottom

[alfrsa]

Hello everyone. I have two Sophronitis coccinea growing on kool-logs and they seemed to be doing fine, but I noticed one of the plants' leaves started yellowing at the bottom, near the pseudobulb.

Both plants have it, but the one on the picture has it worst. It's putting out two new growths (one visible to the left), but had little to no healthy roots when I got it about a month ago.

I grow them under lights, in temperatures of no more than around 20°C (68°F). I have a fan on a timer about half the time, and I have kept the kool-logs filled with distilled water, letting them dry for about a day before refilling. Humidity ranges from 60% (fan on) to 85% (fan off at night). I fertilize with Akerne rain mix at half-strength.

I've looked around online and found a lot of photos of S. coccinea flowering with yellowed leaves at the bottom, but I found as many photos with plain green leaves.

What do you think? Is this a nutrient deficiency? Too much water? Too little light? The yellowing part is firm, but given this species' reputation for needing very specific growing conditions I'm a bit alarmed!

Thank you in advance for your help.

[estación seca]

Welcome to the Orchid Board!

I'm not familiar with that fertiliser. Does it contain calcium?

[alfrsa]

Originally Posted by estación seca

Welcome to the Orchid Board!

I'm not familiar with that fertiliser. Does it contain calcium?

Thank you estación seca!

The label on the fertilizer lists these concentrations:

(11,8N + 2,7P2O5 + 13,7K2O + 11,8CAO + 3,5MGO + 4,8SO3)

The website also lists these micronutrients: Fe, Mn, Zn, Cu, B, Mo and Co.

I think I've read on the board that this is a copy of an american fertilizer which isn't available in europe.

Do you think I should increase the concentration?

[estación seca]

I don't grow this plant, but I grow other Cattleyas. I think its reputation is more because it prefers cooler and more humid conditions than many people can provide.

Yellowing of leaf bases often happens before plants drop them. In Cattleyas this can happen from any one or combination of insufficient water uptake, excessive transpiration loss or inadequate watering. If your plant has few roots it may not be able to take up enough water to maintain all the leaves. It will eventually grow new roots with the new growths, but that may be some time from now.

What does "little to no healthy roots" mean? Did you cut off any roots?

Others more familiar with this plant may have other suggestions.

[alfrsa]

Is the leaf yellowing reversible if the adverse conditions causing it prematurely are corrected, or once started there's no stopping it?

In the pictures attached there's a better view of the root system of both coccinea plants. I didn't cut off any roots and kept all which didn't fall off by themselves. I thought the younger, bushier plant seemed to have healthier roots.

Estación seca, I did add ventilation in the last week... Could that be it, and that - as you said - this increased evaporative stress pushed the plant into dropping its leaves?

[Roberta]

The ideal time to mount a plant is when new roots are just starting. Old roots getting their environment changed will die (but can help keep the plant going until the new roots establish) Yellow leaves will probably not get green again... older leaves usually will just drop off.



If it is starting to root, then that's great. The new roots, and the new growth, are what you need. (Old growths won't bloom either... but they give strength to the new ones) Just a hint, the buds emerge from the leaves of the new growth as they are spreading out... no sheaths. I would not worry too much about daytime temperature - as long as it gets cooler at night, it can tolerate normal daytime temperatures. (I grow it outside, days can get quite warm but nights, even in summer, cool off and let humidity build up)

Have you had success with other plants getting them to adhere to the "cool log"? I haven't... I tried some, ended up just mounting on cork or wood sticks. But yours look like they have a rougher surface than what I could get so may work better. With the new roots, see what this one does. If it doesn't adhere, consider more "natural" mount... I have not found them to be especially sensitive to cooling beyond the normal evaporation of water. They DO need pure water. The Akerne Rain formula is designed for pure (RO, DI, or naturally low-solids water) (I think it is close to the US-available MSU pure water formula) But fertilizer is the least important cultural factor. You have only had the plants a month, they are just starting to root. So this is the time to just observe.