Home
›
Salicaceae
›
Populus
›
Populus trichocarpa (black cottonwood)
synonym – P. balsamifera ssp. trichocarpa (subspecies of eastern balsam poplar)
trichocarpa – hairy fruited
- thrix – hair (Greek)
- karps – fruit (Greek)
Native range: Western North America
Leaves:
- alternate
- simple
- broadly ovate (highly variable & young different than adult
- paler below
- round petioles (genera trait is flat petioles)
Flowers:
- dioecious
- male and female flowers are catkins
- male w/ 40–60 stamens
- female w/ 3 stigmas
Fruit:
- pubescent capsule
- seeds released in spring and may look like snow in spring
Other characteristics:
- tree to 90 ft.
- “Q-tip” shape
- tallest, fastest-growing hardwood in the western US
- lives 100–200 years
- deciduous
- ~brown pubescent branchlets
- leaves have reddish resinous buds with a strong cinnamon scent
- when leaves push through they pick up some of the resin and the leaf underside may appear to have orange blotches, especially in spring and early summer
Ecology & Adaptations:
- native to southern Alaska to southern California, east to the Rocky Mtns in Alberta and Wyoming
- occurring throughout Washington
- found in streambanks and moist woods, moist to wet sites, sea level to mid- elevations in the mountains (up to 5,000 ft in the Cascades)
- forms extensive stands on islands and floodplains along major rivers and disturbed upland sites
- vegetative regeneration:
- re-sprouts from stumps following felling by beavers
- following beaver activity or flood disturbance, branches of a fallen tree may establish new shoots that become trunks
- cuttings of young branches (live stakes) can be used in restoration to plant this species in moist ground
- regeneration in established forests is by root suckers or coppice sprouts
- pollinated by wind
- seed dispersal – cottony hairs attached to seeds aid rapid disseminated by wind and water in late spring
- Adapted to disturbance:
- when moist mineral soil in floodplains is exposed, germination rates are high, particularly when moist conditions persist for a month after seed deposition
- shade-intolerant seedlings rarely establish under parent trees
- suitable conditions for seedling establishment sometimes occur (erratically) in approximately 5 to 10 year intervals
- tolerant of winter flooding (while dormant)
- but requires some aeration of soils during the growing season
- shallow root system facilitates access to oxygen
- tolerant of seasonal hotter, drier conditions – resin covering leaves reduces water loss through transpiration
- fire tolerance:
- mature trees with thick bark may survive low- to moderate-severity fire without top-kill
- younger trees have relatively thin barks that make them more vulnerable to fire damage
- fire creates disturbed areas that may be colonized by wind- or water-dispersed seedlings
- herbivory/microbial defense:
- high terpene and phenolic resin content in buds reduces cellulose digestion, rendering the tissue less palatable to herbivores and less inviting to fungi and bacteria
- resin transferred to leaves as they emerge from the buds provides extended protection
- resin later produced by glands at leaf edges