The maples are famous for their helicopter seeds, but another of my favorites is the American Linden tree, Tilia americana. It makes some big one winged-helicopters with round seeds suspended below. Here they are coming in to bloom. This tree is the source of basswood, which I recently discovered is an excellent wood for making woodcut prints. The tree is also called "Lime Tree" eventhough it has no relation to the citrus trees at all.
