This may be more for a logger but I always liked them. These are the two bumper stickers on my brother-in-law's truck.
#1-Hug a logger, you will never go back to trees.
My friend Jim Assante, owner of Assante Tree Experts just purchased a new 23 ton crane. He called me out to assist in a crane job and check out the new truck. A couple blocks away I caught a glimpse of the boom and rubbed my eyes to make sure that I was seeing correctly. Across the main boom in big red letters, THE ASSMAN. We've joked about it before but I never thought he could pull it off - classic Jimmy
I saw a septic tank cleaning service who's catchprase was 'We're #1 at removing your #2's........made me grin. As for a tree slogan, I always liked 'Arborists do it off the ground'.