Identifying Cottonwood Trees How to find black cottonwood for early-season mushroom hunting in the PNW
Black cottonwood (Populus trichocarpa) is a hardwood that grows along rivers, streams, and lake margins in a region dominated by conifers. It is a useful landmark for spring foragers: some morels and the early Verpa bohemica grow with it, and its dead wood hosts oyster mushrooms.
This guide covers where to find cottonwood, how to tell it from the trees it is most often confused with in Western Washington, and which mushrooms to look for around it. For the tree itself, see the cottonwood tree profile.
Scout Cottonwood Habitat Before You Go
Forayz has a cottonwood layer that shows where it grows, along with public land boundaries and soil moisture, so you can find the general area before heading out.
Where Cottonwoods Grow
Cottonwoods are riparian trees — they need water. In Western Washington, look for them along:
- River floodplains — for example along the Skagit, Snoqualmie, and Chehalis rivers
- Stream banks and creek bottoms
- Lake margins — the edges of lakes and reservoirs, particularly where soil stays moist
- Gravel bars and alluvial deposits — cottonwood readily colonizes fresh sediment (USFS FEIS)
They grow in stands of their own or mixed with red alder (Alnus rubra) and willow.
How to Identify Black Cottonwood
The main features are leaves, bark, and overall stature. Leaves are only useful in the growing season; the rest of the year, rely on bark, stature, and habitat.
Leaves
Oval to heart-shaped with a tapered tip. Smooth, somewhat shiny surface, finely toothed edges, and a pale underside. The buds are sticky and resinous, with a balsam scent.
Bark
Young trees have smooth, greenish-gray bark. Mature trees have thick, deeply furrowed, dark gray-brown bark (USFS FEIS). Bigleaf maple bark is also furrowed, so check the leaves.
Stature
A tall, straight-trunked tree that commonly reaches about 100 feet and occasionally more (USFS FEIS), often taller than the alder and willow around it.
In winter and early spring before leaf-out, rely on bark texture, stature, and habitat. The sticky, balsam-scented buds help confirm it, but check the bark and the leaves once they open.
Cottonwood vs. Similar Trees
In Western Washington, the main sources of confusion are:
- Red alder — Smooth, pale gray bark, even on older trees. Leaves are oval and heavily serrated. Often grows alongside cottonwood.
- Bigleaf maple — Furrowed bark like mature cottonwood, but the leaves are large and deeply lobed.
- Oregon white oak — Lobed leaves; grows in drier habitat such as prairies and south-facing slopes rather than riparian bottoms.
Leaf shape, bark, and riparian habitat together separate these trees from cottonwood.
Mushrooms Associated with Cottonwood
These species grow on or near cottonwood. Check each linked page before eating anything.
Watch Soil Moisture & Temperature
Forayz shows current soil moisture and soil temperature, so you can see how the ground is warming and drying in spring around your cottonwood spots.
Is This a Morel?
Real photos of true morels and look-alikes. Test your ID skills before you hit the field.
When to Hunt Near Cottonwoods
Timing varies with the year, elevation, and weather. As a rough guide for Western Washington:
- Early spring: Verpa bohemica comes up first, usually 1 to 3 weeks before true morels (Arora).
- April–May: Yellow morels (M. americana) near cottonwoods in river valleys and floodplains.
- Fall and winter: Oyster mushrooms on dead cottonwood and other hardwoods.
Morels are generally reported as the ground warms in spring. One study of a European morel found fruiting began at a soil temperature of about 43 °F (Buscot 1989). We know of no Pacific Northwest study of soil temperature and morel fruiting, and none for burn morels, so treat any temperature as a rough cue at best. Cottonwood bud-break is interesting to watch and often coincides with morels, but it is not a reliable timing signal.
Cottonwood & Burn Morels
Burn morels fruit mainly in burned conifer forest the spring after a fire, and why fire triggers them is not fully understood. We have no source showing that burned cottonwood stands are good burn-morel habitat. The Forayz burn perimeter layers show where recent fires were.
Distribution in Washington
Black cottonwood ranges from the Kenai Peninsula of Alaska to Baja California, east to the northern Rockies and Alberta (USFS FEIS). It prefers moist soils and does better along moving water than near stagnant water. In Washington it follows river valleys on both sides of the Cascades.
Sources: Mushrooms of Cascadia (Siegel & Schwarz, 2024); MycoMatch (© Ian Gibson), a compilation of published descriptions through which most other field-guide authors named here are quoted.
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