I wasn't sure if this would go here or the nutrition section. Anyway! We have two huge willow trees in our yard and for some reason I never put it together that willow balls were made from willow trees until, say, recently! Anyway, in the past when I had rabbits outside we used to always give them branches from our willow tree (branches would constantly fall off from wind, etc). We'd give them the branches with the leaves still on. We never had a problem! I did some searching on the web and as far as I can tell, rabbits can eat any part of the willow tree (leaves and branches) but I wanted to double check with everyone on the forum first. Please and Thank you!