I can’t speak on willow sticks that come from other suppliers, but willow is generally a safe chew toy. There have been some discussions about air-dried vs kiln dried.The willow sticks in the Binky Store are all air-dried. Kiln dried can make for harder more brittle sticks. But unless your bunny has a tooth issue or health problem, willow and other bunny safe woods are safe and enriching. Their wild cousins chew wood, brush, hay, straw etc. It’s part of their natural behavior. However, no matter what, if you have concerns with any toy — wood, plastic, cardboard, cloth, whatever it may be, you have to use your best judgement and decide. I always say, if you feel worried, it’s not worth it. Just get something else. You can also always contact your rabbit-savvy vet and get their take on what you are concerned about.
My bunnies have loved willow sticks, Willow wreaths, Willow chunks, Willow Baskets and a variety of Willow toys for over a decade. If it’s willow, it’s like a bunny chew project that they really enjoy. And never has it caused any issues. A while back, I checked with rabbit-savvy vets about the safety of wood toys, plastic toys, etc and they all concurred that while nothing is 100% safe, (Not even hay! as it can poke an eye, and first cut can be as tough as a twig), rabbit’s generally chew things up. That’s what they do! Rabbits chew — they are like birds in that way — always finding something to chew on– if it’s not something like Willow or apple sticks or whatever, it could be your furniture! So it’s a good idea to offer safer enriching toys.