From The Collaborative International Dictionary of English v.0.48:
Poplar \Pop"lar\, n. [OE. popler, OF. poplier, F. peuplier, fr.
L. populus poplar.] (Bot.)
1. Any tree of the genus Populus; also, the timber, which
is soft, and capable of many uses.
[1913 Webster]
Note: The aspen poplar is Populus tremula and Populus
tremuloides; Balsam poplar is Populus balsamifera;
Lombardy poplar (Populus dilatata) is a tall, spiry
tree; white poplar is Populus alba.
[1913 Webster]
2. The timber of the tulip tree; -- called also white
poplar. [U.S.]
[1913 Webster]