perlite vs. pumice in media

[lobotomizedgoat]

I'm curious what people's experience has been with the two. Specifically, whether they differ in terms of water retention, pH, or salt buildup (or anything else that seems worth mentioning).

Perlite is clearly more common, but I like pumice for well draining succulent/cactus mixes. As I just ran out of perlite I'm thinking of using pumice as a small bark additive instead.

[estación seca]

If you compare the same size particles, there's probably no difference. Perlite floats and will separate out at the top of the pot over time, if you water heavily enough to fill the pots with water.

[lobotomizedgoat]

That's one of the reasons I prefer it in my soil mixes. It also floats but it's noticeably less buoyant and seems to migrate upwards less. The extra weight is also nice for things in small plastic pots.

[Roberta]

I particularly use pumice (as a major constituent) in my mix for European and Australian terrestrials. These grow in a mix that is about 80% inorganic (the balance a free-draining potting soil mix) and during the 6-7 months or so that they are completely dry (late spring, summer, early fall) perlite is much too light, so that the pots would tend to blow over. So it does the same thing as perlite, but with more weight, especially important when dry. In a bark mix, I think that they are quite interchangeable.

[Shadeflower]

I came across a good article on orchids and perlite recently:

Simply Hydroponics – Orchids

Mind you it is still quite subjective.

I use a combination of lecca, perlite and pumice in wicking pots.

Each has their own unique properties. I wouldn't really use any by themselves but in the right mix they work great.

Iecca is the airiest and should be used for dry pockets.

pumice is the most wicking. Like pumice will even suck moisture from the air if its humid enough and provide the roots with moisture. It's like a sponge. Too much of it has not brought me any benefits but using a little in a pot can help suck moisture from the bottom of the pot to the top. With certain mixes it drains to the bottom and the top dries too fast so pumice helps.

perlite traps moisture but stays airy at the same time. I use it for seedlings that can't dry out mostly or if a pot dries out too fast.

The main disadvantage I have found with pumice is that it degrades. It isn't quite inorganic like lecca or perlite which will last years and years. pumice I find can degrade like bark and after a couple years if kept too wet can crumble and might need replacing.
I thought pumice lasts as long as lecca but it does degrade. It is quite expensive when you factor in that it isn't forever lasting, it's pricey to start with, then I always have to pick out rocks and sift out the sand in the bag. Then it all needs to be washed. Ok lecca needs to be washed too but it is far less hassle than washing pumice.

I'm using less and less of it, that's not to say I will stop using it, it's just if you use less in a mix, it stays less moist over time and lasts longer.