Are the young twigs, leaf stalks, and leaf under-sides densely covered with velvety hairs?
CLUE: these trees are native to the Pacific coast states, the Southwest, and Mexico.
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Are the young twigs, leaf stalks, and leaf under-sides not covered or sparsely covered with velvety hairs?
CLUE: these trees are native to the eastern U.S. and Great Plains or High Plains, or to Europe; not the Pacific coast or Southwest.