How deep to pot cattleya in S/H so new root growths doesn't become desiccated?

[EleanorChang]

I have foraged the forum, read Rays website, Google etc about "Desiccated Root Tips in S/H" - Now info overload and getting confused - So I thought to directly ask the question

"How deep do I pot cattleya in S/H so new root growths doesn't become desiccated?"

I have also seen a post on this forum where Ray advised a member that their cattleya should sit ontop of of the LECA and not buried init as it can potentially cause rot on eyes and rhizome.

So....

I followed Rays advice and potted my cattleya with the rhizome onto top the LECA. I have a dryline only on the top layer of LECA.
My new root growths are hit and miss: - some grow into the LECA without problem, some show signs of desiccation - I am currently managing the situation by daily misting the top layer and the rhizome also gets wet. I am watering 25ppmN every 3rd day.

What I was wondering.....

Given my existing environment.
For my next S/H repot on any cattleya. Can I bury the rhizome loosely so that it is level with the LECA?

My theory is that if a dryline exist in a my S/H setup, the buried rhizome will stay relatively dryish between flushes (providing I don't mist) and technically the new root growth are growing into an already moist environment - thus preventing desiccation (I know I cannot assume all root grow downwards!)

I might be overthinking a problem where solutions already exist (i.e top dressing sphagnum moss/plastic disc/misting).

No one to talk to about orchids , my husband thinks I have gone bonkers in the last 7 months! ...thought I ask here.

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[estación seca]

No, don't bury the rhizome in the LECA. It needs light. What is the relative humidity in your growing area?

[EleanorChang]

Day: 35-40RH/ Temp:22-26C
Night: 60-65RH/ Temp 17-20C

I have potted them into S/H 1.5 months ago when I first brought it home: so it is sitting on a seedling heat mat 24/7 at the moment on the window sill.
If it is an especially warm/hot sunny day I switch the heat mat off.

[estación seca]

The RH is slightly low for getting established, but acceptable for long-term growth of most Cattleyas. To compensate you could water more often, or use a spray bottle, as you have been doing, to get the roots wet daily.

Also - are the plants firmly anchored? Wiggling around will bump new root tips into the LECA and damage the tips. This can cause roots to stop growing.

[EleanorChang]

Hmm, I consider it well anchored to 4 plastic chopsticks - however, I do move it from the window sill every misting - maybe some wiggling might have occurred.

I'll continue with the misting and see how it goes and minimising moving the pot.

Thank you for your advice, much appreciated.

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[Ray]

The problem is that the LECA pellets on top are too dry, so they are literally sucking the moisture out of the root tips. To prevent that those pellets must be moist.

Raising the humidity is the key, but sometimes that simply cannot be done. As an alternative, some will suggest a layer of sphagnum on top, but I advise against that, as it tends to break down and clog up the air flow. Instead, you might consider a "semi-barrier" to evaporation.

Using a semi-rigid piece of plastic - I like the "acetate" covers used to protects documents - cut a circular piece that's about 2 cm smaller in diameter than the pot. Then cut a straight line from an edge to the center, then remove enough material from the center to surround the base of the plant, giving about another cm of space around it.

Place it around the plant, on top of the medium. You can water normally, as the water will go through the gaps, but the "cover" it creates will slow the evaporation, result in a bit of condensation, and keep the top of the LECA moist.

[EleanorChang]

Thank you for response Ray, I will give that a go aswell and take a pictures.

[EleanorChang]

Originally Posted by Ray

The problem is that the LECA pellets on top are too dry, so they are literally sucking the moisture out of the root tips. To prevent that those pellets must be moist.

Raising the humidity is the key, but sometimes that simply cannot be done. As an alternative, some will suggest a layer of sphagnum on top, but I advise against that, as it tends to break down and clog up the air flow. Instead, you might consider a "semi-barrier" to evaporation.

Using a semi-rigid piece of plastic - I like the "acetate" covers used to protects documents - cut a circular piece that's about 2 cm smaller in diameter than the pot. Then cut a straight line from an edge to the center, then remove enough material from the center to surround the base of the plant, giving about another cm of space around it.

Place it around the plant, on top of the medium. You can water normally, as the water will go through the gaps, but the "cover" it creates will slow the evaporation, result in a bit of condensation, and keep the top of the LECA moist.

@Ray - Here is my attempt - hope these are ok:-

Both are in 5" containers - if I reduce the acetate 2cm smaller - hardly any of the LECA are covered.

Cattleya

• Abit challenging with so many rhizomes in such a small pot; as a result, some parts of it is covered by the acetate.
  
• Condensation is due to the cattleya sitting on a heat mat.

Den-Phal

• The angle of the picture does not do it justice - the den-phal is not as deep in the LECA as it seems to be.
  
• No condensation as it was not sitting on a heat mat.

[KC Kam]

Hi Eleanor and Ray,

I do have the same problem...i am potting in pure LECA (non SH) the top layer dries out very fast.

Do you think a thin layer of coconut fiber will help? It wont breakdown easily yet it dont breakdown into small pieces and fall into the gaps between LECA.

I havent try this yet because i am battling with black fungus / mold that form on the LECA due to too much moisture. Adding the coconut fiber on top might increase them. I am only watering them once a day yet they still grow. -_-"

Not sure whether it will help Eleanor.

[estación seca]

KC Kam, the black layer on top is probably algae or cyanobacteria (blue-green algae.) These are common on media in very humid climates. If blue-green algae, they are probably beneficial, because they can fix nitrogen from the atmosphere, and this may be helping your plants.