The habitats that have been home made are untreated Pine. Aspen is a very good wood used in litter because it doesn’t give off any gasses or odor at all. All woods need to be untreated.

But many folks make toys for bunnies out of wood if you don’t want to go to the trouble.
But here’s a great paragraph on chew toys from the House Rabbit Society website, http://www.rabbit.org:

Chewing
This is perhaps the central concern of most bunny caretakers. Rabbits need to chew, both for physical and psychological reasons. Wicker baskets, non-poisonous logs and sticks, cardboard, paper, straw, and pine cones are all good choices. If Potato enjoys chewing holes into the back of the couch, give her a closed cardboard box filled with paper or straw, with a small hole in it to start, and let her finish the job. Be imaginative! Provide a toy box of untreated wicker or cardboard full of different sizes and shapes and textures of wood, dried-out pine cones, cardboard tubes or other safe items.

Do not give just a chew stick! People often buy these strange orange-and-green wooden sticks from the pet-supply store for their new rabbit, and are surprised to see that Thumper barely sniffs his before starting in on the baseboards. Especially for a young rabbit, or a particularly chew-conscious rabbit, chew-toys need to be interesting (which a chew stick is not, even if it’s dyed orange and shaped like a carrot) and plentiful. The more toys, and the greater variety, the better. A rabbit who has only a stick, a log, or a piece of two-by-four to chew on, is going to be a bored rabbit. And a bored rabbit is a naughty rabbit.

I’d suggest pine, aspen or cedar-ensure it’s totally untreated And on chew toys-mine LOVE balsa…so I wouldn’t make anything out of it

He doesn’t necessarily have to chew on wood. My vet recommends NOT giving them wood to chew on, as splinters can cause issues. he says willow baskets and balls are fine, and hay should be enough to wear down teeth sufficiently.

Gnawing is important for the health of a rabbit’s teeth. The thing is that rabbits enjoy chewing on wood that still has the bark on, they may chew unfinished lumber also but not nearly as much. Try giving your rabbit a large untreated branch from an apple tree or willow.

My bunnies love apple branches- but you need to find a someone with a tree that they do not treat or spray.  My Grandmothers farm has an orchard and when we go there I fill pillowcases with fresh cut branches- leave them in the bags to dry- and then after they are dry and the leaves have fallen off- I cut them into more manageable pieces-about 6 inches or so and store them in a cardboard box.

My bunnies chew all of the bark off unless it is close to knob in the branch that they can’t get their teeth into- within a day- the piece will be naked- and it makes a little bit a brown, fine sawdust.  But they LOVE them.