page_title: Populus
section_title: Description
hierarchical_section_title: Populus / Description
caption_attribution_description: Nederlands: Populier mannelijke bloeiwijze English: Populus x canadensis male inflorescences
context_page_description: Populus is a genus of 25–30 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar, aspen, and cottonwood.
  The western balsam poplar was the first tree whose full DNA code had been determined by DNA sequencing, in 2006.
context_section_description: 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 2 in) in diameter.
  The bark on young trees is smooth, 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 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 of the previous year. The flowers are each seated in a cup-shaped disk which is borne on the base of a scale which is itself attached to the rachis of the catkin. The scales are obovate, lobed, and fringed, membranous, hairy or smooth, and usually caducous. The male flowers are without calyx or corolla, and comprise a group of four to 60 stamens inserted on a disk; filaments are short and pale yellow; anthers are oblong, purple or red, introrse, and two-celled; the cells open longitudinally. The female flower also has no calyx or corolla, and comprises a single-celled ovary seated in a cup-shaped disk. The style is short, with two to four stigmata, variously lobed, and numerous ovules. Pollination is by wind, with the female catkins lengthening considerably between pollination and maturity. The fruit is a two- to four-valved dehiscent capsule, green to reddish-brown, mature in midsummer, containing numerous minute light brown seeds surrounded by tufts of long, soft, white hairs which aid wind dispersal.
caption: Male catkins of Populus × canadensis
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