The term 'Poplar' refers to a type of tree, and there are several varieties of this species. The ALAMO is a type of Poplar that is native to the Mediterranean region and has five letters in its name. ABELE is another type of Poplar that is native to Europe and also has five letters in its name. ASPEN is a type of Poplar that is native to North America and has five letters in its name. COTTONWOOD is a type of Poplar that is native to North America and has ten letters in its name. Finally, Tree is a generic term for any type of plant with a woody stem and four letters in its name.