Inorganic Media ONLY

[Orchid Whisperer]

I agree with the comments about LECA and problems related to water quality. I think those problems could happen with any porous media (perlite, pumice, bark, charcoal, scoria, etc.).

Two "inorganic" media that I suggest checking out that have less porosity, therefore have fewer of the associated mineral build up problems:

1. If you want weight in the pot, go for rock. Avoid marble chips unless you are certain your plant is a strong calciphile. Try granite chips, quartz pebbles ("egg rock" is quartz in larger sizes from home improvement stores), you can even get bags of polished pebbles from dollar stores or hobby supplies. Try pet stores for finer sizes, but inspect the material to be sure it meets your needs. Some rocks still have pores, but usually less than scoria or pumice.
   
2. I have long been a fan of wine corks. Here's a new spin: PLASTIC wine corks are also great! Cork is a great choice when you want a light weight medium. Plastic corks, 3 or more years in the pot, don't look much different from new plastic wine corks, just slightly more soiled. I've noticed that a plant potted the first time in plastic corks may be slower to root and take off. Use corks of any type for Cattleya types and others wanting excellent drainage at the roots.

[Ray]

As has been discussed in another thread, I have found that a 50/50 blend of LECA and Grodan rock wool mini-cubes to be a great medium that has sufficient weight to hold a plant well, while remaining airy and moist.

[Mr.Fakename]

This 50/50 LECA and rockwool mix has been a game changer for me, it's fantastic.

I'm seeing great root growth, and the even moisture in the pot + increased humidity around the plants really seem to make them happy.

[Jmbaum]

Using rock wool is really interesting, does it behave as sphagnum?
Just thought of another factor, are you using plastic pots?
I have everything in clay pots. I’ve potted them well below the rim for a few of my humidity loving species, notably pleurothallis nossax that had leaf failure for months until I did this. It has grown the moss lush and full. Performing much like LECA I’d imagine.

I was checking on the rupicolous Laelias thread, and towards the end people were talking about growing them in sphag instead, wonder how that panned out after a few years and if rock wool would be a good choice.

I’m looking at focusing on acquiring species with unusual growth habits particularly lithophytes, species from dry forest, species that are resilient to a degree. Balancing out affinity for watering and the harsh southern exposure of my growing balcony collection will all be crucial for longterm success. I’ll be anxious approaching Labor Day when last year there was a heatwave reaching 109 F (43 C).

Originally Posted by Ray

As has been discussed in another thread, I have found that a 50/50 blend of LECA and Grodan rock wool mini-cubes to be a great medium that has sufficient weight to hold a plant well, while remaining airy and moist.

Originally Posted by Mr.Fakename

This 50/50 LECA and rockwool mix has been a game changer for me, it's fantastic.

I'm seeing great root growth, and the even moisture in the pot + increased humidity around the plants really seem to make them happy.

[Roberta]

Originally Posted by Jmbaum

I was checking on the rupicolous Laelias thread, and towards the end people were talking about growing them in sphag instead, wonder how that panned out after a few years and if rock wool would be a good choice.

I’m looking at focusing on acquiring species with unusual growth habits particularly lithophytes, species from dry forest, species that are resilient to a degree. Balancing out affinity for watering and the harsh southern exposure of my growing balcony collection will all be crucial for longterm success. I’ll be anxious approaching Labor Day when last year there was a heatwave reaching 109 F (43 C).

Rupiculous Laelias may be a really good match for that hot, bright location. I'd be very hesitant to use a moisture-retentive medium for those. I have been pretty successful with "rupis" mimicking what they get in nature... roots going into the cracks of rocks where there is a bit of organic matter, and moisture. I use a layer of gravel, a thin layer of potting soil, then top it off with more gravel, in clay pots.

[Jmbaum]

Yes, combing through all the species or rup. Laelia to see what is available for my first few. In this moment I'm more interested in the one that have more squat, spherical, and substantial pseudobulbs over the the thinner ones... though figuring out definitively which ones that is another story.

I'll follow suit I'll probable do something similar with potting strategy since our conditions are similar, though I hadn't considered using any soil.

Btw.. I'm about half way through checking all your outdoor species. There are so many I am interested in, I'll have to ask you about some of them.

Originally Posted by Roberta

Rupiculous Laelias may be a really good match for that hot, bright location. I'd be very hesitant to use a moisture-retentive medium for those. I have been pretty successful with "rupis" mimicking what they get in nature... roots going into the cracks of rocks where there is a bit of organic matter, and moisture. I use a layer of gravel, a thin layer of potting soil, then top it off with more gravel, in clay pots.

[Kim in CT]

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]

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!

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.

[Fishkeeper]

Does inorganic-only media require more fertilization? I know most (good) orchid media doesn't break down very fast, but it does break down, so I'd imagine there's some release of nutrients. Rocks and charcoal aren't exactly known for releasing nutrients.

[Shadeflower]

No inorganic does not require more fertilizer.
Barroot plants do not require more fertilizer either.
Bark does degrade and does release nutrients but it's not something we should rely on for nutrients as all is contained in the right balance in fertilizers and feeding the right balance is important, feeding orchids a lot is less important. One big feed will last them a whole month.
But inorganic cannot store nutrients as well as bark so generally it is better to feed much smaller doses on every watering so the orchid always has what it needs at any time.
The downside to inorganic not being able to store nutrients or buffer the feed water in the pots means you do need to make up a lot more fertilized water and you do need to adjust the ph more. Some people would rather just grow a less scientific and simpler approach, not worry about nutrients, ph or water hardness.
A lot of orchids are very hardy, some might not tolerate it but most will. So going inorganic can be seen as more work and harder but it just requires more knowledge, more dedication to get it right but once one has reached that point inorganic makes growing orchids easier.
But inorganic is not as straightforward as growing in bark and it is best to figure out orchids in something that is more forgiving to start with, once one understands their needs better inorganic is a great place to start experimenting.