Willows, in the Salix genera and the Salicaceae family, are shrubs or trees which mainly grow near watercourses and riparian areas. Willows may range from large trees to small shrubs such as coyote willow. They are even found in the tundra where they are only a few inches tall. Willows generally have long green glabrous leaves which may be whitish on the bottoms. Willows form thick shrouds around many creeks or lakes. The chemical which is used to produce aspirin is found in willows; Native Americans would chew willow branches to reduce the pain of toothaches.