Depends on who makes the orchid mix. I use the Miricle grow orchid mix, bark size is smaller than your average Orchid mix. I also mix the MG orchid (non corse) with MG Organic choice and perlite. There are many different Orchid blends so it would depend on which you were referring to.

Mark

I do what Mark does above. I use the MG mix. I would not get or use the Corse mix as Mark states. To corse and it has some sapwood in it. I add a little lime and some pearlite. Works great.

Bill