There's no question as far as I'm concerned. Perlite holds its structure, providing essential porosity throughout the medium for a very long time. It's durable stuff and provides great benefits to a potting medium without turning to mush.

Vermiculite collapses, especially when moistened, almost immediately. How can that be useful? It's not!

I have used it as a propagating medium, but it needs to treated carefully. I'll fill the propagating container with dry vermiculite, then water thoroughly with a misting or spray nozzle. No stirring or touching! After I stick the cuttings, I use the misting nozzle to set the stems. I never handle the vermiculite....no tamping down around the cuttings or the air will be squished from the particles.

I completely agree with Rhizo.

Josh

Hi Gill,

I think they serve rather different purposes. I use Perlite to help aerate the mix & make it more fast draining. As I've had access to Pumice, I also use that for the same purpose. I use Perlite in my houseplants & Pumice in my succulents.

I originally learned about Vermiculite in my Indoor Gardening Group (live, in-person type club) when used in 'soilless mixes' which are equal parts of Peat, Perlite & Vermiculite; that CAN work OK depending on both the plant & the growing conditions.

My sense of Vermiculite is that it's used to help RETAIN moisture. Not something I need, so it ends up I rarely use it. (Actually Vermiculite's only recent use for me has been as filler, to add some weight to some old cereal containers which I use to separate my shelves where I keep my gardening supplies.

The only other use I can think of for Vermiculite is to use it to help lighten up mixes for AV (African violets), which seem to like a fairly light, fluffy & airy mix.

No choice in my mind, but if a choice btwn the two, it's Perlite all the way!!!

Thanks for the replies and opinions everyone, looks like the perlite has the yes vote!
Must say that I've not had any problems with it 'collapsing' in my mix, maybe because iit was screened? When I repotted this spring, chunks of it were still plainly obvious, roots had pieces attached to them and it can still be seen on the top of the mix in my pots.
Cheers, Gill UK.

I've mentioned many times that I still have 3+ gallons of the 2 - 2 gallon bags of vermiculite I bought 15+ years ago. Vermiculite and perlite serve different purposes in a mix, so it's difficult to compare their performance one against t'other. For stability and it's ability to help ensure aeration & drainage, I'm in the same camp as the majority who regularly use perlite as a fraction of their media.

Al

Thanks Al, perlite it is, and I now know why thanks to you all.
Gill UK

Gill,

You got some great answers that I agree with. If you haven't yet read Al's classic treatise on container potting media, you really should.

Didn't see it mentioned above, but perlite doesn't really "increase drainage" - it reduces water retention, and creates micropores by functioning to separate other materials, like bark.

Follow the link, and be prepared to spend some quality time.

Daniel

Here is a link that might be useful: container culture