I found this really cool rock that I want to use to do a root-over-rock
style bonsai with. With this in mind, I went out and bought a chinese
elm. When I got it home and took it out of the pot though, the roots
were so overgrown that they were like one of those things you scrub
your dishes with. I tried squirting the root ball with a hose to try
and wash some of the dirt out of it, but after 20 minutes of that it
still just looked like a bunch of roots compressed into the shape of a
pot. There was no way I was going to be able to untangle the roots
without ripping half of them.

What should I do? Plant it in the ground for a year and let the roots
losen up? Or will that not help anything?