The Biology of Populus

Poplars (trees of the genus Populus , family Salicaceae) are deciduous, opposite-leaved, fast-growing trees that naturally occur in moist habitats at many elevations and latitudes (Brockman 1968). In North America, there are 15 species of poplars including black cottonwood (Populus trichocarpa ), the non-native Lombardy poplar (Populus nigra var.italica ), and quaking aspen (Populus tremuloides ). Poplars often establish where a disturbance has occurred, or where a branch, broken off in flood waters, takes root where it is deposited! Especially in the intermountain West, black cottonwood is a dominant riparian species, providing ecologically valuable shade and erosion control in the riparian corridor. Poplars are dioecious, and the propagule module is a number of tiny seeds embedded in a mass of fine fibers closely resembling cotton. These modules are wind-dispersed, and can even present a significant allergy hazard in areas where poplars have been extensively planted. Poplars also clone themselves naturally, and this propensity for vegetative reproduction has proven useful in the establishment of poplar cultures. Another advantage due to this trait is a method of stand regeneration known as coppicing. Coppicing is allowing the stumps to sprout following harvest, rendering any form of planting unnecessary.

	Black cottonwood is an important tree in many ways. It is the most widely distributed poplar in the intermountain West south of Canada, and is a common riparian species. Mature trees are 90-120 feet tall and 3-5 feet in diameter at the base. It is a parent species for many of the hybrids being developed.
	Eastern cottonwood grows along riparian zones and in moist woodland areas. Like the black cottonwood, it is frequently used in the development of new clones.
	Quaking aspen is an outstanding tree in many regards. The wind-dispersed seeds readily establish themselves in disturbed landscapes, helping to reforest mountain slopes after a fire. This species also forms clonal stands with an even canopy. The bark is an important winter browse for high country herbivores such as deer and elk. The aspen is aesthetic as well- the slightest breeze will set all the foliage to "trembling", creating one of the most beautiful sights the mountains have to offer.
	The balsam poplar has the largest range of any poplar in North America, covering much of Canada, Alaska, and some of the United States. It grows along streams like most poplars, and can be found in association with willows (Salix spp.) Moose are known to enjoy the cambium as a browse food.

Return to Hybrid Poplar Intro