Black cottonwood

Black cottonwood (Act) - Populus trichocarpa

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Geographic range and ecological amplitudes 


Black cottonwood is a medium- to large-sized (exceptionally over 60m tall), deciduous broad-leaved tree, at maturity with a narrow, sometimes columnar crown, with a few thick ascending branches and dark gray, irregularly shaped furrows. Many kinds of wildlife use the foliage, twigs, and buds for food. The wood is light and soft and is used for lumber, veneer, and pulp.

Geographic range 

Geographic element:
Western North American/Pacific and Cordilleran

Distribution in Western North America:
north, central, and south in the Pacific region; central and south in the Cordilleran region

Ecological amplitudes 

Climatic amplitude:

(subalpine boreal) - montane boreal - cool temperate - cool mesothermal (absent or marginally in hypermaritime climates)

Orographic amplitude:

submontane - montane - (subalpine)

Occurrence in biogeoclimatic zones:
(lower MH), (lower ESSF), (MS), BWBS, SBS, (SBPS), (BG), (PP), IDF, ICH, CDF, CWH

Edaphic amplitude:

Black cottonwood

Range of soil moisture regimes:
slightly dry - fresh - moist - very moist - (wet)

Range of soil nutrient regimes:
(poor) - medium - rich - very rich

The edaphic amplitude of black cottonwood is very similar to that of balsam poplar. The major ecological difference between the two species is in their climatic requirements. While balsam poplar is mainly a subarctic or boreal tree, black cottonwood grows mainly in temperate and mesothermal climates, only marginally in subalpine boreal climates.


Tolerances and damaging agents

Root system characteristics

On floodplains, the root system of black cottonwood is multi-layered, owing to the deposition of new soil by periodic flooding. Although early root development is downward, subsequent growth progresses upward as root development occurs on the buried stem. Lateral root spread can be >15m. Roots are associated with ecto- and endo-mycorrhizae.


Tolerance to Tolerance class Comments
low light L a very intolerant, exposure-requiring species
frost M lower in coastal populations
heat M absent on insolated sites
water deficit L absent on water-deficient sites
water surplus H tolerates flooding and strongly fluctuating water table well; intolerant of brackish water
nutrient (mainly N) deficiency L absent in acid, very poor soils


Damaging agents

Damaging agent Resistance class Comments
snow M high snowfall will break branches rather than boles
wind H high winds will break the boles rather than uproot trees


  Risk class  
fire L fire risk in cottonwood stands is very low
insect L not a major concern
fungi L not a serious concern [heart rots (for example, brown stringy trunk rot of hardwoods)]; leaf rust (Melampsora spp.)
other agents L not a major concern; browsing by large ungulates; root browsing and girdling by voles and mice

Associated tree species and successional role

In British Columbia, black cottonwood grows predominantly in even-aged, pure stands, and, in the later stages of primary succession on floodplains, with many shade-tolerant conifers. Black cottonwood is a pioneer species (primary succession) on floodplains, and is present in early seral and mid-seral stages of secondary succession on floodplains and upland sites.

Associated tree species
tree species
Occurance class Major area of occurance
western redcedar M generally replacing black cottonwood in the final stage of primary succession in cool temperate and mesothermal climates
sitka spruce M only in maritime climates
red alder M floodplains in southern coastal B.C
white spruce (& hybrids) M mainly in boreal climates
trembling aspen L mainly in boreal and cool temperate climates
lodgepole pine L cool temperate and montane boreal climates
black spruce L BWBS
bigleaf maple L southern coastal B.C
grand fir L southern B.C
subalpine fir L mainly in ICH


Silvical characteristics

Characteristic Interpretive class Comments
reproduction capacity H a high potential for vegetative reproduction from root and stump sprouts; the flowering stage is reached at an age of about 10 years
seed dissemination capacity H dispersed by wind and water
potential for natural regeneration in low light L practically nil; a shade-intolerant and exposure-requiring species
potential for natural regeneration in the open H especially on mineral soil; segments of stems and buried branches greatly contribute to regeneration
potential initial growth rate (<5 years) H up to 2m in one growing season in cuttings
response of advance regeneration to release na advance regeneration does not develop in the absence of adequate light
self-pruning capacity in dense stands H if initial stand density is high
crown spatial requirements H short but wide crown is necessary to support rapid growth
light conditions beneath closed-canopy, mature stands H associated with well-developed understory vegetation
potential productivity H site index (50 yr @ bh) >30m on productive sites
longevity L generally <200 years


Genetics and notes


Black cottonwood exhibits considerable variation throughout its range. Balsam poplar and black cottonwood hybridize and produce frequently mixed populations where both taxa are sympatric or even where they are separated by rather large distances. This hybridization may be considered intraspecific (see balsam poplar).


Bell, D.S. 1990. Populus trichocarpa. Pp. 570-582 in R.M. Burns and B.H. Honkala (technical coordinators) Silvics of North America, Vol. 2. Agri. Handbook 654, USDA For. Serv., Washington, D.C.

Black cottonwood produces in a short time (?30 years) high yields of wood suitable for mechanical pulping. Considering its productivity, vegetative reproduction, and low risk of being affected by damaging agents, it is a suitable species for intensive management on flooded sites. More detailed silvics information is given by: