Populus is a genus of over 60 species of deciduous flowering plants in the family Salicaceae, native to temperate, subarctic, and montane regions of Eurasia, North America, and North Africa, and to the tropical highlands of East Africa. English names variously applied to different species include poplar ( ), aspen, and cottonwood.
The western balsam poplar (P. trichocarpa) was the first tree to have its full DNA code determined by DNA sequencing, in 2006.
Description
Mature trembling aspen trees (P. tremuloides) with young regeneration in foreground, Alaska
The genus has a large genetic diversity, and can grow from 15–50 m (49–164 ft) tall, with trunks up to 2.5 m (8 ft) in diameter.
Male catkins of Populus × canadensis
The bark on young trees is smooth and white to greenish or dark grey, and often has conspicuous lenticels; on old trees, it remains smooth in some species, but becomes rough and deeply fissured in others. The shoots are stout, with (unlike in the related willows) the terminal bud present. The leaves are spirally arranged, and vary in shape from triangular to circular or (rarely) lobed, and with a long petiole; in species in the sections Populus and Aigeiros, the petioles are laterally flattened, so that breezes easily cause the leaves to wobble back and forth, giving the whole tree a "twinkling" appearance in a breeze. Leaf size is very variable even on a single tree, typically with small leaves on side shoots, and very large leaves on strong-growing lead shoots. The leaves often turn bright gold to yellow before they fall during autumn.
The seeds of the poplar tree are easily dispersed by the wind, due to the fine hairs surrounding them.
The flowers are mostly dioecious (rarely monoecious) and appear in early spring before the leaves. They are borne in long, drooping, sessile or pedunculate catkins produced from buds formed in the axils of the leaves from the previous year. The flowers are each seated in a...
