Populus balsamifera
Where their ranges come into contact, this species will readily hybridize with "Populus balsamifera", "Populus deltoides", "Populus fremontii", and "Populus trichocarpa". These hybrids can form extensive populations in some regions. Due to the frequency and morphological consistency of "P. angustifolia" × "P. deltoides" hybrids, they were initially described as a fully separate species ("P. acuminata") until its hybrid origin was firmly established in the 1980s.