buttonball tree

from The Collaborative International Dictionary of English v.0.48

Buttonwood \But"ton*wood`\, n. (Bot.)
   The {Platanus occidentalis}, or American plane tree, a large
   tree, producing rough balls, from which it is named; --
   called also {buttonball tree}, and, in some parts of the
   United States, {sycamore}. The California buttonwood is
   {Platanus racemosa}.
   [1913 Webster]