Whats this?
 

Hi all, I was unpotting a Onc. wildcat and noticed what looks like many white rocks but they are easily crushed with your fingers and in crystalline consistency. I was thinking that it could be salt but I've have never seen this. Any Idea?

I think that is just chunks of perlite.

That's it! Coarse perlite. It's used to hold water in bark mixes.

Well that makes me feel better. Thanks

Just wanted to make a correction on this. I was reading 'Understanding Orchids' and on Page 71 they show a pictures of all the different types of medium and these little rock looking things are actually White Pumice. Coarse perlite is not that big.

Now you have me worried, Ross! I didn't think that perlite held water. I thought it was to help create air spaces within a bark or sphag medium and to help the mix drain well. If what you say is correct, then I've been doing things wrong -- maybe that's why I kill some of my plants. :scratchhead:

Shirley, I think it is supposed help hold some moisure and creates a more open mix. Every premixed bag of bark or coconut husk chips I buy has it in it or I mix in some of my own. I don't think it causes any problems with holding too much moisure. Heres a link from Rays webside that describes a bunch of potting media including perlite if you scroll down. Hope that helps! :biggrin:

Choosing Potting Media

Thanks Sarah. That's a very useful website.

Sorry, Ross, if I seemed to be contradicting you. I've always used coarse perlite to open up my mixes but I just never thought of it being water retentive! Always something new to learn! :duh: