Water pH

[Ray]

Semi-hydroponics has the advantage of maintaining a very stable root zone environment, compared to more traditional culture. Watering daily has absolutely nothing but a positive effect on the plants. Conversely, it can also play a role as a "watering frequency buffer" if you can't water frequently.

I had a paph hybrid in a 6.5" pot that bloomed-out in my kitchen, then I took it to my basement (dry, cool, dark) to divide and repot it. I let it go for a while, then had to go to Canada to help a family member getting out of the hospital, then came back and caught up on orders, so all-in-all, that plant sat unattended for six weeks. The slow release of the moisture from the LECA kept it just fine for the duration. Once placed back in the greenhouse, it jumped right back into active growth.

I certainly don't recommend that kind of mistreatment, but it protected the plant from my inaction.

Unlike fertilizer in that other thread, when it comes to watering, "more is better than more".

 

[Linus_Cello]

Conversely, it can also play a role as a "watering frequency buffer" if you can't water frequently.

Conversely, it's an idiot proof method to prevent root rot. I've had neighbors take care of some of my orchids for vacation, and I tell them NOT to have the pot sitting in water... can't do that with the side holes in s/h.

 

[Justin]

Finally got out the pH indicator...

Water out of tap = 8.5
Irrigation solution 1/16 tsp (or a smidge more)/ gallon 30-10-10 = 7.0
Runoff from 4" pot w/1 year old fir bark mix = 6.5
Runoff from 4" pot w/ 1 month old orchiata mix = 7.0

 

[Stone]

Ray, What's the story with LECA accumulating salts? Does it (LECA) have any sort of CEC? (if not, I presume that it can be flushed at any time to lower salt content). I was told by one grower here that there was a problem of salt build up but he was using it only as an ingredient in traditional potting not permanently wet as in SH etc. Have you monitored EC of the well water over time and is flushing/watering with nutrient better for maintenance as apposed to just topping up the well with plain water with periodic feeding?

 

[Ray]

Mike,

Most brands of LECA have extremely low CECs. In inorganic materials, it tends to be the edges of clay particles that play the biggest role in that respect, and in a fired clay body, those edges have mostly been thermally modified or even vitrified.

Mineral buildup, therefore, is merely the "sponge effect", less than a case of being bonded to the substrate. Consider this scenario:

Pellet saturated with a liquid containing dissolved solids. Every pore contains the same solution. As the water at the surface begins to evaporate, those dissolved solids migrate toward the center of the pellet, as physics tries to eliminate the concentration gradient. Eventually, when enough of the solvent has evaporated, and a solubility limit has been reached, precipitation occurs.

Rewetting it may redissolve some of that precipitate, but not all of it, so by repeating those resaturate/redry cycles leads to visible buildup.

I will add that in the situation of LECA in S/H culture, if done in a high-humidity environment that does not favor evaporation, that buildup rate is VERY low, so you can get away with long periods between necessary repotting. If one often sees the tops of the medium dry out, then more frequent repotting is required - it may only need the top inch or so replaced, but it is something to consider.