Jobi statted this (about a month ago).

"About the leaves, don’t crush them, just throw them in a pile over your other substrate, you can compress them a little with your hand. These leafs help in retaining moisture, your lizards will love them for sure."

And Ingo said the leaves in his enclosures were about 4 inches thick.

I have collected leaves but haven't put them in the tank yet. The washing question is a good one. I'm curious too.
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BONNIE