Poplar
| Poplar, Aspen, Cottonwood | ||||||||||||
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 Western Balsam Poplar foliage | ||||||||||||
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| Sect. Populus Sect. Aegiros |
Populus is a genus of trees which includes the cottonwoods, poplars, and aspens, all of which are sometimes termed poplars (in some areas "popple").
Poplars are deciduous, and the leaves turn bright gold to yellow before they fall during autumn. The leaves of many poplars, including the cottonwoods and aspens (but not the balsam poplars), 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 water pipes as they will crack walls and pipes in their search for moisture.
Poplars of the cottonwood section are often wetlands or riparian trees. The aspens are among the most important boreal broadleaf trees.
Poplars and aspens are important food plants for the larvae of a large number of Lepidoptera species - see List of Lepidoptera that feed on Poplars.
Classification
- Populus section Populus - aspens and white poplar. Circumpolar subarctic and cool temperate, and mountains farther south (white poplar warm temperate)
- Populus tremula - Common Aspen, Trembling Aspen or Eurasian Aspen. Europe, northern Asia.
- Populus tremuloides - Quaking Aspen or Trembling Aspen. North America.
- Populus grandidentata - Bigtooth Aspen. Eastern North America.
- Populus adenopoda - Chinese Aspen. Eastern Asia.
- Populus sieboldii - Japanese Aspen. Eastern Asia.
- Populus alba - White Poplar. Southern Europe to central Asia.
- Populus × canescens (P. alba × P. tremula) - Grey Poplar
- Populus section Aegiros - black poplars or cottonwoods. North America, Europe, western Asia; temperate
- Populus nigra - Black Poplar. Europe.
- Populus × canadensis (P. nigra × P. deltoides) - Hybrid Black Poplar
- Populus deltoides - Eastern Cottonwood. Eastern North America.
- Populus fremontii - Fremont Cottonwood. Western North America.
- Populus petrowskyana - Russian Poplar. Europe/Asia.
- Populus nigra - Black Poplar. Europe.
- Populus section Tacamahaca - balsam poplars. North America, Asia; cool temperate
- Populus angustifolia - Willow-leaved Poplar or Narrowleaf Cottonwood. Central North America.
- Populus balsamifera - Ontario Balsam Poplar. Northern North America.
- Populus trichocarpa - Western Balsam Poplar or Black Cottonwood. Western North America.
- Populus laurifolia - Laurel-leaf Poplar. Central Asia.
- Populus simonii - Simon's Poplar. Northeast Asia.
- Populus maximowiczii - Maximowicz' Poplar. Northeast Asia.
- Populus section Leucoides - necklace poplars or bigleaf poplars. Eastern North America, eastern Asia; warm temperate
- Populus heterophylla - Swamp Cottonwood. Southeastern North America.
- Populus lasiocarpa - Chinese Necklace Poplar. Eastern Asia.
- Populus wilsonii - Wilson's Poplar. Eastern Asia.
- Populus section Turanga - subtropical poplars. Southwest Asia, east Africa; subtropical to tropical
- Populus euphratica - Euphrates Poplar. Southwest Asia.
- Populus ilicifolia - Tana River Poplar. East Africa.
- Populus section Abaso - Mexican poplars. Mexico; subtropical to tropical
- Populus mexicana - Mexico Poplar. Mexico.
Flowers
The flowers are dioecious and appear in early spring before the leaves. They are borne in long, drooping, sessile or pedunculate aments which are produced from buds formed in the axils of the leaves of the previous year. The pistillate aments lengthen very considerably before maturity. The flowers are solitary, each one seated in a cup-shaped disk which is borne on the base of a scale which is itself attached to the rachis of the ament. The scales are obovate, lobed and fringed, membranous, hairy or smooth, usually caducous. The staminate flowers are without calyx or corolla and consist simply of a group of stamens, four to twelve, or twelve to sixty, inserted on a disk; filaments short, pale yellow; anthers oblong, purple or red, introrse, two-celled; cells opening longitudinally.[1]
The pistillate flower is equally destitute of calyx and corolla and consists of a one-celled ovary seated in a cup-shaped disk. The style is short, stigmas two to four, variously lobed; ovules numerous. The fruit is a two to four-valved capsule, ripening before the full development of the leaf; greenish or reddish-brown. The seed is light brown and surrounded by a tuft of long, soft, white hairs.[1]
Cultivation and uses
Fast-growing hybrid poplars are grown on plantations in many areas for pulpwood and used for the manufacture of paper. The wood is generally white, often with a slightly yellowish cast. It is also sold as inexpensive hardwood timber, used for pallets and cheap plywood; more specialised uses include matches and the boxes in which camembert cheese is sold. Poplar wood is widely used in the snowboard industry for the snowboard "core", because it has exceptional flexibility.
Poplar was the most common wood used in Italy for panel paintings; the Mona Lisa and indeed most famous Early Renaissance Italian paintings are on poplar.
Due to its tannic acid content, the bark has been used in Europe for tanning leather.[1]
There has been some interest in using poplar as an energy crop/biofuel, particuarly in light of its high energy in/energy out ratio, large carbon mitigation potential and fast growth.
In the September 2006 issue of Science, it was announced that a species of poplar, Populus trichocarpa, was the first tree to have its full DNA code sequenced (published in full here).
Poplar is also a wood that, particularly when seasoned, makes a good hearth for a bow drill. Poplar was picked as the material for the bones of "Buster", the crash test dummy used in the TV show MythBusters, after some experiments revealed that it fractures under approximately the same loads as human bone. Poplar is sometimes used in the bodies of electric guitars and drums.
Populus is among the oldest type of dicotyledonous plants. When sequoias, pines and cycads made up the bulk of the Cretaceous forests of Greenland, the poplar alone of deciduous trees was present.[1]
References
External links
- Poplar cultivation in Europe
- Balsam Poplar - Populus balsamifera Large-format diagnostic photos and information on poplar hybrids.
