What is the spongey stuff that houseplants come in sometimes?

[Loren]

I have some shallow hanging planters that I plan to use to winter over geraniums. I think the spongey stuff that some houseplants come in will work with some pebbles in the bottom. They don't have drain holes.
What is that spongey stuff called? Where can I purchase it?
Thanks!

 

[Chuck]

Probably peat moss if it is fibrous and it can be purchased at any garden center. But a word of advice. It contains zero plant nutrients. It is acidic and it retains moisture.

 

[Loren]

It is not peat moss. It is more like a sponge and it is not fibrous.
Thanks for trying. It retains moisure like a sponge does.
I've seen it in poinsettias and other hothouse plants.

 

[Chuck]

It is not peat moss. It is more like a sponge and it is not fibrous.
Thanks for trying. It retains moisure like a sponge does.
I've seen it in poinsettias and other hothouse plants.

Check out horticultural sponge on google.