Inorganic Media ONLY - Orchid Board

Jmbaum · #1 04-09-2021, 09:40 PM

What is everyone’s thoughts on using solely pumice and/or charcoal? I hesitate on Leca because of what I’ve head about alkalinity over time. I don’t mind watering more, if it means healthy ventilated roots/ less chance of rot.

What should I be worried about?

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Any other ideas to consider?

estación seca · #2 04-10-2021, 12:26 AM

LECA, charcoal, pumice, wine corks, bark chips, sphagnum moss, cinders, gravel can all work fine. It depends on your conditions and how you grow.

Ray · #3 04-10-2021, 07:32 AM

I am curious where you got the info about LECA and increasing alkalinity with time. Alkalinity is the resistance to pH change, usually due to the accumulation of carbonates in the medium, and they often come from hard water, not from the medium itself.

Besides, for the most part, LECA brands are pretty much neutral.

Charcoal is not an inorganic medium, being wood that has not been fully burned.

Jmbaum · #4 04-10-2021, 12:37 PM

So the LECA info was from... YouTuber switching her collection into LECA and was getting those results

2020 Orchid Recap - Why I gave up LECA, Jewel Orchids, cool growers & more! - YouTube

You’re probably correct about it coming from the water. That is definitely something I consider using LA tap water, I’m thinking of adjust pH down to offset this. I’m around 7.4 and want to go to just above 6 if practical for any sensitive plants. I’ve been having good luck with flushing the pots with warmer water, perhaps a more acid flush on occasion would do well. Still need to check the pH of the tap with each of the fertilizers I go between.

With charcoal, I’m considering it relative to sphagnum fir bark and the like. I will likely include a small amount of fir in the mix just for comfort.

Quote:

Originally Posted by Ray

I am curious where you got the info about LECA and increasing alkalinity with time. Alkalinity is the resistance to pH change, usually due to the accumulation of carbonates in the medium, and they often come from hard water, not from the medium itself.

Besides, for the most part, LECA brands are pretty much neutral.

Charcoal is not an inorganic medium, being wood that has not been fully burned.

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Also Ray, looks like you have some fantastic information on your site, I’ll comb through later today.

DirtyCoconuts · #5 04-10-2021, 12:55 PM

That you tuber is straight up wrong lol

I consider charcoal in-organic due to its longevity and almost totally resistance to any fungus but Ray is correct. It behaves differently when in a wet sphag and bark mix than an open and airy basket with rocks. I have some in baskets at least 5 years old. Still the same as when I put it there.

I am a big proponent of inorganic

Leafmite · #6 04-10-2021, 01:36 PM

When selecting a medium, just realize that not all orchids are the same. I grow nearly everything in red lava rock but I have a few that really prefer NZ sphagnum moss or being mounted...and that is what they get. I will probably switch the Phaius to a light potting soil/sphagnum/bark mix but the Phal bellina really loves the moss so she will stay in it. But this is in my growing conditions and everyone has a different environment and level of care.

Kim in CT · #7 04-12-2021, 10:49 PM

Quote:

Originally Posted by DirtyCoconuts

That you tuber is straight up wrong lol

I also saw this YouTube video, right after I moved most of my orchids to S/H. Although I'm a new orchid grower, I am an experienced chemist and I thought this sounded strange. I repeated what the YouTuber did and could not reproduce those results. For me, the pH coming out of the drainage holes (after a 30 min soak) was the same as the pH going into the container.

If there was something in the LECA that was leaching out to make the draining water alkaline, then it would react with acid. I took some LECA and soaked it in a range of hydrochloric acid solutions between 6 M and 0.5 M for a week (I teach high school/college chem) and observed very little change in mass. Nothing was reacting. My conclusion: LECA is fine.

I'll also note that pH meters can be very flaky and inconsistent, especially near neutral pH. The little meter I bought online to use with my plants gives quite different results (up to 2 pH units) compared to the calibrated pH meters at my school.

Jmbaum · #8 04-13-2021, 01:16 AM

Big yes to running your own experiment! I wonder regionally if impurities in the clay would create a difference. I’m going to get water to pH to about 6 anyways. So no longer overly concerned with a slightly alkaline media.

I’m going pot with pummice and charcoal primarily, add a layer of larger LECA as bottom and top layer primarily by for weight and larger air pockets. I think with the same size sphere it gets me minimum 25% air pockets, if I remember sphere packing correctly.

I’m be using an aquarium pH kit to test by color, rather than digital. A 2 unit margins of error for pH is yikes!

Quote:

Originally Posted by Kim in CT

I also saw this YouTube video, right after I moved most of my orchids to S/H. Although I'm a new orchid grower, I am an experienced chemist and I thought this sounded strange. I repeated what the YouTuber did and could not reproduce those results. For me, the pH coming out of the drainage holes (after a 30 min soak) was the same as the pH going into the container.

If there was something in the LECA that was leaching out to make the draining water alkaline, then it would react with acid. I took some LECA and soaked it in a range of hydrochloric acid solutions between 6 M and 0.5 M for a week (I teach high school/college chem) and observed very little change in mass. Nothing was reacting. My conclusion: LECA is fine.

I'll also note that pH meters can be very flaky and inconsistent, especially near neutral pH. The little meter I bought online to use with my plants gives quite different results (up to 2 pH units) compared to the calibrated pH meters at my school.

DirtyCoconuts · #9 04-10-2021, 02:57 PM

Well said Leafmite. That IS the most important consideration

estación seca · #10 04-10-2021, 03:10 PM

Minerals on LECA come from the water. If you use water with low mineral content, or if you water the LECA so it doesn't dry completely, minerals will not build up on the LECA to any extent. I use my tap water with dissolved minerals of 800-1,200 parts per million (=mg/l) on some plants in S/H. With frequent watering I don't get mineral buildup.