Populus × acuminata or Populus acuminata, the lanceleaf cottonwood, is a species of Populus native to the Rocky Mountains of North America. It is a naturally occurring hybrid of narrowleaf cottonwood, Populus angustifolia, and eastern cottonwood, Populus deltoides, found where their ranges overlap. It is planted as a shade tree in cities in the Rockies, preferring to grow at elevations between 4,500 and 8,500 ft. Given the plant's proclivity (Wikipedia)