I, too, can only offer my Cym a rather dry environment, and it's indoors... my plant is only a backbulb that I'm trying to grow. It sprouted fine, and is still growing, but I still have a little learning to do.

I'm using a mixture of small fir bark pieces, coarse perlite, and to help maintain a bit more moisture, I've cut up a couple of strands of the longer sphag moss and mixed it in. So far, so good... however, keep in mind that we live at opposite sides of the equator, and each individual environment will be different.

I'm far from expert, so perhaps some more experienced growers will come to the rescue with better advice... anyone?

I like medium coconut chunks for keeping a bit more water in my stuff. Or maybe you could just add a bit of coir to the type of mix you already use? I just found a brick of it in the garden section of Menard's, of all places and repotted my Nobile Den in a mix of baby bark, medium charcoal, and #4 sponge rock held together with coir.

Thanks for responding.

I'm thinking that these are what I can add to my cym mix so it would retain MORE moisture:
coconut chunks
coir
sphagnum moss
(Are there others?)

These DON'T retain much moisture:
bark (Smaller pieces would more than larger pieces, right?)
LECA
charcoal
sponge rock
Perlite

Is that right?
So I would add more of the first group to the mix to retain more moisture?

There was a mix developed by the Rod McClellan Co. that may be similar to those available at stores like OSH or Home Depot for cymbidiums. It is basically decomposed bark with nutrients added as well as other organics, including sand. To help this type of mix last some growers have used packing pellets as an ingredient in the mix.
To make something comparable with locally available products you might want to start with decomposed granite that would be available at any landscaping products store, combine with any type of low cost compost, available at Walmart, and the finest grade of landscaping bark you can find. Mix the three together in equal parts and be sure to fertilize with an appropriate fertilizer.

For myself, I've found that keeping the medium particulate ingredients comparable in size helps tremendously. And for me, I try to separate organics from inorganics when it comes to the majority of ingredients in container growing.

I've learned that organic ingredients, meaning materials that break down quickly, like peat or compost, and don't provide the root structure with a source of readily available nutrients already broken down for immediate intake, are best saved for the garden... while working with ingredients that hold their structure longer, and at the same time, provide for good aeration and drainage, support for the plant, and eliminating a perched water table, are more beneficial. And I prefer to be the one in control of nutrients and moisture amounts, so I feed a liquid plant food mixed in a weak solution every time I water.

I would agree with granite pieces, and bark... as long as they're comparable in size... but if it were me, I'd nix the compost and go with something like a mixture of turface, very coarse perlite, and if you must have an ingredient that allows for more moisture retention, I'd go for a handful or two either high quality potting soil, or cut up pieces of sphagnum moss.

I don't want to confuse you, or step on anyone's toes... but since Cyms seem to be grown in medium that is closer to an actual soil mixture than an open orchid bark, there are a few things growers should be aware of when it comes to the basics of soils and how water moves through them.

The link below contains an excellent article on the basics of soils... science and physics, broken down into easy to understand terms. It helped me tremendously in choosing various ingredients for different plant types. I think it might help... or at least give you a little insight into the basics.

Happy Growing!

Here is a link that might be useful: Container Soils - Water Movement & Retention XV

Very interesting reading Jodik. But I prefer a stratified type of substrate and the use of net pots which is an entirely different scenario than the extensive analysis given at the link you provided.
For cymbidiums my preferred pot is the most open type of
container I can find, such as the Sterilite Mini Crate or a net pot, into which I place the cymb and bottom fill with coarse bark, covering with a mix of finer bark, hard wood leaves, and shredded bark fibers such as aspen fiber, and then top dressed with natural green moss snugging in around the base of the orchid. This mix provides great aeration and some water retention.
In growing other types of plants uniform mixes may be suitable for typical commercial nursery grown plants in the usual type of plastic pot (1 gallon) but may not be as beneficial unless some adjustment as to substrate depth in lieu of the nature of the plant due to its tendency to retain moisture above a level of long term tolerance of some plants. For example, Dudleya and Lewisia species which I grow with the pot lying on their sides and using substrates that drain rapidly but retain moisture. Cultural techniques also limit the effectiveness of a commercial mix which will break down irregardless, unless the majority of the substrate is of inert materials such as gravel.
All in all, there really is no one method of developing a substrate that is universal in scope as each individual grower practices their own unique methodology in culture. It is tying the how to the means that is what is needed to find some degree of assurance in cultural success.

To make something comparable with locally available products you might want to start with decomposed granite that would be available at any landscaping products store, combine with any type of low cost compost, available at Walmart, and the finest grade of landscaping bark you can find. Mix the three together in equal parts and be sure to fertilize with an appropriate fertilizer.

This should work well. In addition you could track down the recipe for Al's famous 'Gritty Mix' and see if you can source the ingredients locally. It's very similar but, minus the compost, should last longer in your pot.

Pot size shouldn't matter, small, medium or large take your pick. You want more water retention, increase the Turface faction of the 'Gritty Mix'.

Thank you all so much for the info you wrote above.
Today, I'm repotting my cyms again. I'm finding that the smallest ones have all dead roots, but there are new ones growing from below the new green shoots. My medium sized cyms have a couple of live roots, but mostly dead, along with some new roots.
To make my new potting mix, I sifted the largest pieces (1/2" and larger) out of the potting medium I used before: bark, charcoal, and some LECA. I added some peat moss and some very small pieces of sphagnum moss. I also sifted and added some Miracle Gro Orchid Potting Mix, which looks similar to my homemade mix.
I'm hoping at least one of my cyms will be healthy enough by next fall to bloom. :-)

My largest cyms (still medium size) had mostly healthy roots, so I repotted them into the same mix they were in.

Wow! This is a little intimidating. I am a long time gradenweb lurker, but this is my first time in the orchard forum, and I came here looking for advice for re-potting a cymbidium near the California central valley. It gets hellishly hot and dry, from early may through late October, and growing things in anything other than a self watering container seems futile.

For fifteen or so years, mine has been blooming in a large (10 gallon?) black plastic pot under three redwoods in the front yard. I have done NOTHING for them. There would probably have been more blooms if I had. They did not bloom this year, and when I went to check the pot, it wouldn't move. Turns out redwood roots had gotten in and taken over half of the pot.

Right now I have several "pseudobulbs" and "back bulbs" (if I understand what I am reading) in a pot with a mix of regular potting soil and some peat moss. I have a brick of coir from a citrus growing escapade. Can I do something with what I have, or will I be happier getting some orchid medium?