There are lots of "rules" when repotting - depends on who'se advice you take.
I never use material like styrofoam. First of all I think the material is a blight for the landfills, second, I prefer bark mixes (just my preference. Third, there is not as many crevices for roots in the rather large chunks typical for styrofoam.
Oh! I forgot the second part to your question. Size of pot is entirely governed by desires of the species being repotted. Many like the roots tight and you typically don't repot as often. Many like lots of growing area for roots to spread (Phaelenopsis is one) because they typically grow on trees, rocks, etc. in nature and prefer some room. You'll probably notice Phals sending roots over sides of pots if too tightly potted.
Thanks Ross. I appreciate your quick reply. I want to repot my new phals asap. Any tips on size of pot? if you look at my pictures in the thread...'bought 2 new phals' from yesterday....you may be able to advise me whether to size up or not...thanks very much!
For phals I use the pots that are big enough to accomodate all roots without breaking, but not bigger. Hope this will help.
That's the key! If pot is too big, medium will rot before roots occupy space. Shadow has the idea here, just big enough to accomodate all the viable roots (including any that might have been outside pot befor you decided to repot.)
Thanks again, I really needed this info!!...Where might I find info on what species vs size of pot? Or is it just from experience?
For other species, it's from following this web site for a while Search all the genera areas (Phals, etc.) for your questions. There's a ton of infor here. I've been following this wonderful board for a while now and have forgotten all the threads I was once part of . Eventually it just sinks in as to what makes sense for each generic plant group. Each has their own desires.
Excellent info on repotting space! thanks to everyone.
I now repotted one of the two...the biggest struggle I've ever had! I can't believe all those thick roots fit into a that little 4" narrow pot!!! It gave me a big problem trying to get it into a 6", but at least I had the depth. The roots were determined to go straight down.
I hope it all works out okay.
I'm so lucky I found this great forum...all of you are fantastic!