LECA surrounded by Sphagnum

[Ray]

In any container, it isn’t a matter of the “top layer” being dry, with the rest wet; it’s a gradient.

There are two, competing processes happening - wicking that moves liquid upward from the reservoir at a fixed rate (unique to the medium used), and evaporation, which varies based upon many factors, with relative humidity being the most significant.

Buildup of minerals and waste does not only happen at the top. It’s a gradient process, as well.

Having W>E is the “ideal” situation, because it minimizes (note I did not say “prevents”) buildup by both slowing precipitation and allowing a more thorough flush when watering, and by having the top of the LECA column stay moist, the potential issue of newly-growing root tips becoming desiccated upon contact with dry, mineral-laden pellets.

Sure, one can work on the moisture-distribution side of the disparity by adding something that wicks faster, but it is advantageous to work at slowing the evaporation side. Besides shifting the pot more to the “ideal” side of the balance, adding humidity is better for the plants.

[Shadeflower]

that was well put Ray.
I also often have the sun affect my pots in a way that the sun side gets heated and condensation forms on the shady side of the pot.
I showed a Cattleya that was being grown on the wet side but that was an example of what not to do so I will also include a phal being grown on the "dry" side which works better than one might think. I know what you might think - look at all that algae yes that is the point of semi-hydro to have constant humidity but my top roots are dry.
This one is still flowering well and it is recovering from spider mite damage.

[Marcia Ann]

I use pots from Easygro Hydro for all my S/H. Has a little gauge to tell you the water level, inner and outer pot, plus they include a nice leca with each order. The pot come in different sizes from 2 inches up, and you have a choice of outer pot color or black or white.

[Ray]

Originally Posted by Marcia Ann

I use pots from Easygro Hydro for all my S/H. Has a little gauge to tell you the water level, inner and outer pot, plus they include a nice leca with each order. The pot come in different sizes from 2 inches up, and you have a choice of outer pot color or black or white.

Jeree Harms, who founded the company, is the guy who introduced me to LECA in the first place, and he and I were partners at shows and when importing material for a few years.

I like the 3-component pots for houseplants, but not so much for orchids.

For one, it is possible to overfill the pot, potentially drowning the roots. Back when I had a greenhouse full of orchids and was commuting to work at 6 am, I didn't have the time to check each pot individually for water level, so the converted deli container was a better option.

Secondly, that design encourages the grower to just "top up" the reservoir, observing the gauge. Doing that accelerates the buildup of wastes in the medium and solution. They should be disassembled, the outer pot dumped, the LECA flushed, then reassembled and refilled with fresh solution at every watering.

The third negative to me - particularly if you have a lot of plants - is the cost.

[katsucats]

I don't know that roots would instantly die upon meeting mineral deposits touching the velamen. At least in my experience, this has never happened. Mineral deposits are more visible on LECA, but I can't imagine why any other medium wouldn't also have them, including medium that must dry between watering, like bark.

[SouthPark]

With LECA ----- it is pretty good at wicking. So it might be like an elevator or conveyor belt ----- where the chemicals are in solution form, and the direction of travel is upward ----- and then it gets to the dry region and precipitation occurs ----- or turns into solid form up the top, and accumulates.

The bark etc probably doesn't have the same sort of movement. But I think that ------ too much of anything (too much fertiliser ----- or too frequent application) --- is not good for the orchids.

[Ray]

Originally Posted by katsucats

I don't know that roots would instantly die upon meeting mineral deposits touching the velamen. At least in my experience, this has never happened. Mineral deposits are more visible on LECA, but I can't imagine why any other medium wouldn't also have them, including medium that must dry between watering, like bark.

It’s not so much the mineral deposits as it is the porosity of the LECA, and that’s mostly an issue to the surrounding environment.

If the LECA is quite dry, it can literally desiccate a root tip that comes in contact with it.

[SouthPark]

True - and that's where it all goes back to the area of checking to make sure that the growing environment and conditions remain satisfactory. So what could be done to prevent the LECA from drying out too much up top ------- which could involve adding particular materials (rock wool etc), or even machine systems for humidity control etc.

[Clawhammer]

My most successful s/h plants are ones that develop a layer of moss on top. Flushing every day and adding a little sphag/rockwool to the top layer of LECA expedites this process.

My s/h rockwool experiments have gone pretty well so far. I would probably recommend it over sphag.

[WaterWitchin]

I wish I could get moss to grow on the top of my pots. Then again, I'm sure no water-every-day kind of person. Never tried using sphag in SH, because it seemed counterintuitive. I started using LECA in SH for the inorganic and less repotting, plus no guessing about when to water. There are easier ways to solve the dry line by experimenting other than adding an organic material.

The rock wool, I agree, so far it appears to work well. I'm finding I do only prefer adding it to plants that are "thirstier" rather than all. Keeps me from having to water in between times when I WANT to water.