LOL The Austrailian bottle trees go outside only in summer. I have a "grove" in a big shallow bol, and one little one that's struggling because I'm trying to play with its roots and probably not watering it enough. I agree with being in awe at the specimens at the Arboretum!
I do have some maples started (from Muddy's yard) and may try bonsai with one or two... also have a baby cedar? that needed a home at the end of a swap. I bet some of the many Rose of Sharon seedlings could be tried as bonsai also... would they make tiny blooms? who wants one? or 12?
There are some red maple babies (1 - 3 ft) out there also (I think our big "Autumn Flame" maple has started producing lots of seeds)... so if anybody is looking to add maples, please say so and I'll get some dug (I can't dig them, but my nephew can!)