''This article is about woody plants of the genus Populus
Populus is a genus of trees which includes the cottonwoods, poplars, and aspens, all of which are sometimes termed poplars.
Poplars are deciduous, and turn bright gold to yellow before their leaves fall. The leaves of many poplars, including cottonwood and quaking aspen, have laterally-flattened stems, so that breezes easily cause the leaves to wobble back and forth, giving the whole tree a "twinkling" appearance in a breeze.
Like willows, many poplars have very strong and invasive root systems, so they must not be planted too close to houses or waterpipes as they will crack walls and pipes in their search for moisture.
Poplars of the cottonwood section are often wetlands or riparian trees. The quaking aspen is one of the most important boreal broadleaf trees.
- Populus section Populus - aspens and white poplar. Circumpolar subarctic & cool temperate, and mountains further south (white poplar warm temperate)
- Populus tremula - Common aspen or European aspen
- Populus tremuloides - Quaking aspen
- Populus grandidentata - Bigtooth aspen
- Populus adenopoda - Chinese aspen
- Populus sieboldii - Japanese aspen
- Populus alba - White poplar
- Populus x canescens (P. alba x P. tremula) - Grey poplar
- Populus section Aegiros - black poplars or cottonwoods. North America, Europe, western Asia; temperate
- Populus nigra - Black poplar
- Populus x canadensis (P. nigra x P. deltoides) - Hybrid black poplar
- Populus deltoides - Eastern cottonwood
- Populus angustifolia - Narrowleaf cottonwood
- Populus fremontii - Fremont cottonwood
- Populus section Tacamahaca - balsam poplars. North America, Asia; cool temperate
- Populus balsamifera - Eastern balsam poplar
- Populus trichocarpa - Western balsam poplar or Black cottonwood
- Populus laurifolia - Laurel-leaf poplar
- Populus simonii - Simon's poplar
- Populus maximowiczii - Maximowicz' poplar
- Populus section Leucoides - big-leaf poplars. Eastern North America, eastern Asia; warm temperate
- Populus heterophylla - Swamp cottonwood
- Populus lasiocarpa - Chinese necklace poplar
- Populus wilsonii - Wilson's poplar
- Populus section Turanga - subtropical poplars. Southwest Asia, east Africa; subtropical to tropical
- Populus euphratica - Euphrates poplar
- Populus ilicifolia - Tana River poplar