Inorganic media

[Johndeaux22]

For the last few years I’ve been repotting in various mixes of bark/leca/large perlite/coconut husk “croutons” depending on the needs of the plant I’m repotting. I’ve had good luck with the mixes I’ve been making, however, I’m considering moving more towards purely inorganic mixes for most of my plants going forward. Obviously, I won’t make this change all at once, and don’t generally repot anything “just because”. My main motivations for going this route are to allow me to disturb the plants as little as possible during repotting, as well as to allow me to automate some of my watering. During the busiest season for my business, 80+ hour weeks are the norm rather than the exception, and trying to get my family to look after things the way I’d like, isn’t always possible.

I’m curious what other people are having success with. My collection is very Cattleya heavy, both species and hybrids, with a liberal helping of various dendrobiums of different stripes, as well as a few odds and ends. I know I won’t be able to put everything into the same mix, but I was thinking with various proportions of leca and rockwool cubes I could probably build a mix that would suit most of my collection, and deal with the outliers appropriately.

[Louis_W]

I highly reccomend Semi-Hydro. Every plant: pure leca, and plants cant really be overwatered so its great for when fiends water plants for you. I grow mostly bifoliate, and other species Cattleyas and they are great in SH. It allows me to drop intact rootballs into new larger pots without really changing their environment. Perfect for sensitive roots. Im sure most Dens would also like it.

I water about once a week in winter and every 4 days in summer.

[Ray]

Many outdoor growers in Florida use LECA in “normal” pots for “traditional” culture, as the stuff cannot rot, which is a real issue when there is that daily, early-afternoon rain.

My collection, consisting of phrags, paphs, and phals, is in 100% inorganic media, ranging from LECA in S/H to a mixture of LECA and Grodan rockwool mini-cubes for more “traditional” pot culture.

Whatever you decide to do, be sure to repot just as new roots are emerging from the base of the plants. You’re going to lose roots no matter what, but that minimizes the impact.

[WaterWitchin]

Everything I grow potted is in semi-hydro, LECA medium. All on baker racks in a sun room in windows with extra LED lighting. Temps are lows of 65-69F winter and up to 90F summer. Been doing solely semi-hydro since around 2012 or so.

Plants with higher moisture needs, e.g., phrags, paphs I mix in Grodan cubes and also adjust depth of reservoir depending on moisture requirements of the plant. Lots of different genus, because I'm eclectic that way.

Usually water once a week, 100-125 plants, takes me about twenty minutes if I'm just watering. Mounted plants are on timed automister and I run water over them whenever I water the rest.

[Johndeaux22]

Thank you for the ideas. I’m not ready to make the change to s/h exclusively, but am considering moving a few plants over eventually.

I already only repot when I see new roots, unless something is seriously amiss. I fully expect the process of switching over to inorganic media to take a few years, as a lot of my collection has been repotted in the last year.

[Leafmite]

Years ago, I grew mostly standard Cattleyas along with a mix of others but I have downsized to smaller orchids.

When I grew the larger Cattleyas, I used the one inch lava rock. If you use basket pots, moving it to a larger pot is just setting it into a larger pot with more rock, no need to disturb the roots. I always potted them into a pot that would allow growth for many years, though. The rock and basket pot allow plenty of air-exchange so rotting roots are not a concern.

Now that I grow smaller orchids, I use 1/4 inch lava rock. Like with the larger rock, the roots of the orchids I grow can grip the smaller rock so that, after a time, if I knock over the pot, most of the rock will stay in the pot.

What I am growing in the 1/4 inch rock:
small Cattleyas, Zygos, a Dracula, a Paph, two Phals, a Psychopsis, three small Oncidiums (Twinkle and the parents), and some Cyncs. Except for the Dracula (small basket pot due to the way it flowers), I use pots that have small holes all over for increased air-flow.

If you do choose lava rock, rinse the rock either outside or in a bucket that is dumped outside as the dust can clog sinks. Flush the rock well, now and then, with water to get rid of any excess fertilizer that is unused. Always stake and wire the orchid very well in the pot when it is first planted as the rock can scrape, cut roots if the orchid moves. Once the roots are well-established, this is not a problem. I would pot the new Cattleyas in the rock in the spring and, by the time I brought them inside in autumn, I could remove all the wires/stakes. If you have any rootless Cattleyas, just stake them over the rock and water the rock well when you water the other orchids. The humidity will help the new roots grow.

If you have any smaller orchids, mounting is another option. I have a nice collection of small mounted orchids, including a Cattleya walkeriana. I was thinking of mounting the Cattleya schilleriana and aclandiae but they are doing well in the 1/4 inch lava rock and I hate to disturb them.

[WaterWitchin]

I've read numerous threads regarding your use of lava rock, Leafmite. Curious... do you just buy lava rock like you'd get from a big box store that some folks use for landscaping? It was one of the filter medias folks used to use in pond building a couple decades back. Only drawback from a filtration standpoint is you'd have to refresh it at least yearly because the pond gunk would get down into the holes.

Also, and knowing different climates thus different culture, but how often do you need to water using lava rock as a medium? I'm thinking about a spring project for outdoors and gathering some different medium ideas.

[Leafmite]

Hi!
My conditions are variable because...Ohio. In days past, we had dark, dreary, cold winters and the home would be cooler and the light would be dim (sliding glass doors, south-facing). Summers can be cool, wet, dry, hot...one never can predict them. Winter has changed, though. Now we have very sunny warm winter days which are a bit of a nightmare as it can get pretty hot in that window. I have to water the rock in the mornings when a warm winter day is predicted.
I have been using lava rock since the early 2000's. I started growing orchids sometime in the 1990's, according to photos (can tell by the ages of the kids). Before lava rock, I used bark and it would always become compacted at some time during the winter and my orchids would be rootless by spring (somehow they would survive to sufer another winter). Lava rock was a game changer. Until recently, the landscaping lava rock was what i always used. The landscaping lava rock is nice because it can be found everywhere, a large bag is CHEAP and you can sort through it and use the different sizes for different orchids (the largest pieces are great for the bottom of a pot). I used it for everything, including large Paphs (I watered them every day). I watered the Standard Cattleyas, Dendrobiums, Oncidiums, Vandas, and Angraecums twice a week in this set up. At first, I used clay pots but then moved to basket pots around 2011 (when I joined an orchid society and found them!).

I now buy much more expensive 1/4 inch lava rock on Amazon for Bonsai. It is proving to be a great medium for orchids that like NZ sphagnum moss as well as the smaller Cattleyas and Oncidiums. I hate paying so much for it but it is cheaper than the moss and lasts forever so, in the end, it is a bargain. Fortunately, most of the orchids I buy are mounted or small so I do not need to buy too much of it.

If you use the rock, as I mentioned, rinse it well outside. The one thing I do not like about it is the initial dust and that, until the roots get established and hold the orchid steady, you just do not want to move the orchids around too much as the rock can damage the roots if the orchid wriggles in the pot. Also, flush the medium well. I always let the rains do this each summer and then fertilize very lightly during the winter.

I like to experiment so I have tried many other mediums and I have to say that lava rock is my favorite (I also like mounted orchids but, well, some orchids are just easier to grow potted in my conditions). The orchid roots really grip onto it and I like never needing to change the medium. I had orchids growing in the same rock over ten years without issue.

[WaterWitchin]

My conditions are also variable, although summer is always hot and rarely wet.... Kansas.

I started dabbling in orchids around the same time period. Bark medium and I never got along well either. Have a couple of plants I need to transition to semi-hydro, and a few phals that have climbed out of the pot. Think I'll grab some lava rock and give it a go with some. I do want to stick to the semi-hydro concept because of not wanting to water often. Will be interesting to see how well it wicks. Thanks for sharing your culture with us.

[estación seca]

Fred Clarke spoke to our society last month. I haven't written up my notes yet, and he agreed to review them before I publish them here. He addressed the issue of inorganic medium. He said orchids do better if there's some organic medium mixed in the inorganic, the better to support the beneficial microorganisms. He said it doesn't take much to have the effect. That made me think.

When I put newly-arrived plants into S/H I don't remove all the old medium. I shake off only what is loose, so as not to damage all the roots and leave the plant unable to take up water before forming new roots. Small plants in sphagnum, like those Ellen at Olympic Orchids ships, I put into S/H without disturbing the root ball at all. Ray points out old roots will die because they aren't adapted to the new environment. I have noticed most of my plants keep most of their old roots.

Leafmite, do you have bits of leaves, sticks and seeds of trees like maple and elm getting into your lava? I could imagine it would be hard to remove without damaging roots.