The trees at the arboretum usually have some form of identification nearby as you can see below. This species of platanus is also known as the American sycamore, American planetree, occidental plane, and buttonwood. Although they grow as far north as the extreme south of Canada, this one at the arboretum is the only one I have ever seen.
The mottled bark often flakes off, one of the means used to identify this tree.
References
Platanus occidentalis
Dominion Arboretum
Images
Photos from my Canon SX620 HS at the Central Experimental Farm's Arboretum, Ottawa, Canada.
@kansuze