I bought a 10" deep plastic wading pool in anticipation of planting a Darmera, Petasites, or Astilboides since I've read that they like wet conditions and need to be contained to prevent rampant spreading (at least the first 2 do.) Is 10" deep going to be deep enough? Should I punch a few holes in it?

The spot I have in mind is shaded from morning till evening by surrounding trees. Which one would be the best for deep shade?

Thanks for your help!

(If you have one of these to trade, check out my exchange list!)