Black cottonwood is a large, fast-growing deciduous tree native to western North America. It reaches heights over 100 feet and widths over 35 feet, with furrowed gray bark and an open crown. It blooms in early spring with catkins containing separate male and female flowers. Its fruit is a dry pod that splits to release fluffy seeds. It provides habitat and food for birds and insects. While prone to fungal diseases, it is useful for shelterbelts, windbreaks, and shade but requires space away from structures due to invasive roots.

1. Black Cottonwood – Populus balsamifera ssp. trichocarpa
(POP-you-lus ball-sam-IF-er-a TRY-ko-kar-puh)
Family: Salicaceae (Willow Family)
Native to: Much of western Northern America from AK to Baja; in S. CA in protected valleys and
canyon bottoms, along stream banks, and edges of ponds and meadows, typically in sandy soils.
Woody tree
mature height: 100+ ft.
mature width: 35+ ft.
Large tree with open crown. Trunk of mature trees is thick, covered with furrowed gray bark.
Winter-deciduous. Fast growth rate, particularly when young. Moderate lifespan (< 75 years)
although may live to 150-200 years. Extensive and invasive roots – can damage pipes, drainage
systems & foundations (plant 40 ft from buildings).
Growth characteristics:
Blooms in early spring. Flowers on drooping branches (catkins).
(separate male & female trees). Fruit is a dry pod which splits releasing fluffy seeds.
Blooms/fruits:
Dioecious
Uses in the garden: Most often used for shelterbelts & windbreaks. Also makes good shade tree on
large sites. Does fine with deep summer water and near streams/ponds. Nice scent and fall leaf
color (yellow). Takes up excess nitrogen from soils. May be slightly allelopathic (toxic to other
plants); also, dense shade from spring through fall may limit plantings beneath these trees.
Sensible substitute for: Non-native poplars; other large non-native shade trees.
Excellent bird habitat: provides cover, nesting sites and nectar/buds for food. Important
early source of pollen & nectar for native pollinators and other insects. Larval food source for
several native butterflies.
Attracts:
Requirements:
Element
Sun
Soil
Water
Fertilizer
Other
Requirement
Full sun best; may tolerate very light shade
Any except alkali
Regular deep watering; shallow watering=shallow roots. Tol. seasonal flooding.
Does best with light fertilizer (every few years) or organic mulch; fine with none
Prone to fungal diseases and damage from poplar and willow wood borers; let soil
dry out at least yearly to prevent fungal rots.
Most important is to locate this tree away from waterlines and structures. Also, not
good under power-lines due to height. Prune diseased and weak limbs to prevent wind breakage.
Management:
Propagation: from seed: short viability; plant fresh seeds, spring
by cuttings: when dormant
Plant/seed sources (see list for source numbers): 1, 3, 7, 8, 11, 13, 14, 20
12/9/10
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