Hey! That's funny you asked that. I just bought a magazine yesterday called Animal Wellness and they have an article in there about feeding fruits and vegetables. The article is entitled Top Ten Fruits and Vegetables. Here's a summary.
"The following ten fruits and vegetables are majour players when it comes to the health and well being of our feline and canine family members."
3. Green Beans
5. Sweet potatoes
6. Tomato (disclaimer, I've always heard not to feed tomato to your dog)
8. Blueberries and cranberries
The article goes on to say that "Our animals don't have the necessary enzymes to break down the cellulose walls, which are indigestible carbohydrates found in the outer layers of fruits and vegetables like apples, broccoli, green beans, and carrots. We have to break down the walls for them, so these power-packed foods become as bio-available as possible. This can be accomplished in a variety of ways:
*A food processor
*Cooking or steaming
I have fed my dogs carrots, sweet potato, green beans, bananas, and apples with no problems at all. My terrier could not handle the broccoli but then again I didn't break it down for her because I didn't know you were supposed to!
I would avoid celery unless you find out it is good for them. Celery can be hard to digest and it really does not have much nutritional value (for humans, anyway).