One of the national symbols of Canada is the maple leaf, it is even on our flag, yet, unlike the Moose or the Beaver, Maple trees are more common in the states than in Canada. Which made me wonder, why is the maple leaf associated with Canada when the tree is found is more common in the states?
According to this research the symbolism was developed by Canadiens living along the St Lawrence River by the early 1700s. The coats of arms for Quebec and Ontario (est. 1867) each feature a triple maple leaf design, and that might suggest some lineage of the maple leaves standing in for the triple-fleur-de-lis (i.e. yellow iris) that symbolized the French monarchy that sponsored the original colonization.
If I had to go out on a limb, I'd guess the some early Canadien saw enough maple leaves floating into the St Lawrence in autumn that he thought it'd be funny to lampoon proper Bourbon symbolism with them, and over time (and various English incursions) it evolved from snarky to serious.