5. Sweetgum tree
The species is beautiful, especially in autumn. But the main issue is the tree’s spiny balls of brown color. They come down in thousand and there are a lot of ways these balls cause injury. People can slip on them or, which is even less pleasant. Or they can shot out of a lawnmower and become a dangerous projectile. You cannot rake them easily. Most of those who grow the tree pick the “gumballs” by hand.