[Jack Garcia]

The only trees I know for sure are safe for gnawing are fruit trees (apple, pear, etc). Rose bushes are also safe (they're distantly related to apples and other pomes).

Freezing doesn't kill all parasites, but baking at 200F/94C+ for an hour will.

My neighbors' field has a bunch of apple trees in it, and they let me pick an armful of branches every couple of weeks. If your mice are anything like mine, they won't play on the branches as much as they will slowly EAT them.

 

[Jack Garcia]

You're very welcome!

The best place for toxicity information I think is probably parrot groups. Parrot owners deal with the whole "which branches are good for my animals" thing quite a lot, I'd imagine.

 

[Jack Garcia]

I hadn't thought of cherry!

Dandelions are safe for mice or people. They taste rather bitter to me, but the mice seem to love them. If you have little kids around, they make a really fun time out of picking them for the mice. I had some around a couple months ago and I gave them a bowl and let them play "harvest time" where they went around the yard and picked dandelions for the mice.

Then I let them feed them to the mice and they got a real kick out of that.