WSU Clark County Extension
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Black Cottonwood

Scientific name: Populus trichocarpa
Taxonomy
Family:Salicaceae
Type:Deciduous tree
Native:YES
Plant Requirements
Zone:5 to 9
Sun:Full sun
Moisture:Medium
Plant Characteristics
Height:150 ft
Width:40 ft
Bloom:Fragrant flowers
Bloom Time:April to May
Bloom Color:White
Additional Characteristics
Trees


Fruit

Leaves


Bark
Wildlife value

Poisonous
Description As the largest of the American poplars, Black Cottonwood is also one of the largest hardwood trees in western North America. This species is also known as Black Poplar.

  Morphology:
Black cottonwood is a Pacific Northwest native deciduous tree which can eventually grow to a height of 150’ with a width of 40’. The limbs bear alternate leaves which are simple, broadly ovate and 3”-5” long. The base of the leaves can be either wedge or heart shaped. Leaves are dark green on their upper surfaces and silvery green on their lower surfaces.

Black cottonwood is normally a dioecious species, with male and female catkins produced on separate trees. Trees begin to flower after 10 years of growth. Male catkins are 1” long, and produce up to 60 stamens. After releasing their pollen, male stamens are shed. Female catkins are up to 3” long and bear copious amounts of silky tufts, referred to as “cotton”, which contain small seeds (2-4 valved capsules). The cottony hairs help carry the seeds in the wind. Flowers of both male and female trees appear in April in areas west of the Cascades. In urban settings the cotton of the Black Poplar is often considered messy.

The bark of Black Poplar is gray-brown in color. As for texture it has flat-topped ridges alongside V-shaped grooves. During the winter buds are well known for their length (up to an 1”), their orange-brown color, and their balsam fragrance.

  Adaptation:
Black cottonwood grows on a variety of soils and sites, from moist silts, sands, and gravels of aquatic islands and river bars to rich humus upland sites. While it prefers the wetter sites it is considered drought tolerant.

  Pests:
None reported.
For assistance, contact Dr. Charles Brun (brunc@wsu.edu), (360) 397-6060 5701
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