Rock Wool Medium

[WaterWitchin]

Originally Posted by estación seca

The evaporative cooling will be directly proportional to the loss of weight, since the cooling is directly proportional to the evaporation of the water.

For some reason ES, that phrase reminds me exactly of what the Scarecrow said after receiving his brain.

My experiments, based on a very unscientific method... let's call it experiments in practicality, have been going well.

I repotted seven or ten-ish plants with differing amounts of rock wool strategically layered into the area just atop where the reservoir stops, and a layer or so below the top of the pot. Ones where I already knew I was struggling with a too low dry line for the plant. Still mostly LECA. In a couple that were really tall pots, a third small layer in the middle as well.

ALL are doing much better with holding the dry line much higher than before. I was impressed with the difference. I'm not wanting to use rock wool instead of LECA, as it gets yucky looking after awhile, and it makes my hands itch. Just using as a "boost" of the dry line. I'll try to take a couple of picture examples later today showing the difference in similar containers.

[WaterWitchin]

So pictures. Not great pictures, but still. These were all watered three days ago. I tried to pick ones with similar height, size, reservoir size, etc. First one hasn't been modified. You can barely tell what's wet and what isn't. On this one, it's dry from about an inch or so above the reservoir hole. It's an established phrag and always thirsty.



All three were having the same issue of a too low dry line prior to repotting these two with a little rock wool.

This one the top and part of a second layer of LECA are dry. But I used non-soaked LECA to repot, so think it's fine and will increase by next watering. I split when repotting, and one on right side with whiter roots I re-transitioned so now roots are down in LECA. Before they were laying on top of LECA and it was attempting to crawl over side of pot.



This one, another thirsty one, has moisture all the way to only top layer of LECA being mostly dry.



A significant difference, for me. Worth repotting more and incorporating a little rock wool into.

---------- Post added at 02:45 PM ---------- Previous post was at 02:44 PM ----------

PS It isn't Bill Nye type scientific, but I think you'll still get the drift.

[Ray]

I think the "mixed-in" approach will work better than the single layer.

[WaterWitchin]

Why do you say that Ray? Because it’s doing what I want, which is decreasing the level of the dry line which is now almost nil. Please elaborate.

[Ray]

Originally Posted by WaterWitchin

Why do you say that Ray? Because it’s doing what I want, which is decreasing the level of the dry line which is now almost nil. Please elaborate.

I view the individual cubes as being “mini-reservoirs” in the LECA column. With them scattered throughout the material, the distance the water has to be wicked is small, but in the layer you showed, it has greater distance to travel.

Maybe in your current conditions it’s fine, but if your conditions changed to favor really fast evaporation, it might still outstrip the wicking, driving the “dry line” down.

Sure, a mini-reservoir closer to the surface is going to give up its water faster than one lower down, but considering the water-holding capacity of the cubes, I’m not concerned it’ll be significant.

Just speculation...

One thing for sure - folks concerned about traveling and leaving their plants for a long time should definitely consider adding some rock wool to their potting media!

[WaterWitchin]

Originally Posted by Ray

...
Maybe in your current conditions it’s fine, but if your conditions changed to favor really fast evaporation, it might still outstrip the wicking, driving the “dry line” down.

Sure, a mini-reservoir closer to the surface is going to give up its water faster than one lower down, but considering the water-holding capacity of the cubes, I’m not concerned it’ll be significant.

Just speculation...

One thing for sure - folks concerned about traveling and leaving their plants for a long time should definitely consider adding some rock wool to their potting media!

For me, I'm already in the driest evaporation time of the year. The it-just-snowed have-furnace-on crap we call winter. Blech. So pretty sure I'm good.

I don't travel... too many dependent animals. But I would certainly agree on that one. Rock wool has been around for plant use since forever, but I've not seen in used much in the orchid world before, other than plugs for seedlings. It's used in aquatic plants a LOT; especially the ones grown non-hydroponically that sit in a bag on a shelf for months (like aquarium trade). I wonder why.

Here's speculation on that subject...I guess partially I was reacting to your "mix" of LECA/wool cubes on the previous page. To me that seems like way more wool that LECA... too much for my taste. Yes, lots of spaces in it, in a plain old dumped into pot. The issue I'm having is when repotting and incorporating those cubes into my mix. Just having it mixed in with LECA, no problem. But getting it in and around the roots of the growing plant, having to tap, poke, shake, prod with a chopstick to get it into the middle or down the sides. Especially with something Oncidium with the tremendous amount of fine roots. It gets too packed with rock wool compressing as I try to nudge it into place. That's why I just slowly drop in pieces here and there, and save the LECA for the tamping down part.

[Ray]

In my example mix, it was 50/50 by volume. Is that much needed? I doubt it, but don't know for sure.

If the cubes are saturated when you mix them with the LECA, they blend in more thoroughly. If they're dry, the LECA tumbles to the bottom and you're left with the cubes at the top.

[DirtyCoconuts]

i have a device i made from an old swing arm lamp that holds the orchid in place while i place the medium around it...i am unable to get any decent SH setup when i try to pour in the LECA with the plant on one side...this gently holds it in the middle so i can carefully place those tricky little pieces to fill gaps

[B727]

@WaterWitchin @Ray
How are you working with those cubes, are you wearing gloves?
In the past I made some really bad experiences with rock wool fibers.

[Ray]

Originally Posted by B727

@WaterWitchin @Ray
How are you working with those cubes, are you wearing gloves?
In the past I made some really bad experiences with rock wool fibers.

I wear gloves when measuring out dry cubes for repackaging, but once they are wet, I have not bothered.

So far, no issues.