Identifying Cottonwood Trees How to find black cottonwood for early-season mushroom hunting in the PNW

Black cottonwood (Populus trichocarpa) is one of the most important trees for early-season mushroom hunting in Western Washington. While our region is dominated by conifers, cottonwoods grow along rivers, streams, and lake margins — and they’re among the first trees to signal that spring mushroom season has arrived.

If you’re looking for morels, oyster mushrooms, or dryad’s saddle in March through May, learning to spot cottonwoods from a distance will save you hours in the field. The good news: Western Washington has fewer deciduous species than the East Coast, so identification is straightforward once you know what to look for.

Where Cottonwoods Grow

Cottonwoods are riparian trees — they need water. In Western Washington, look for them along:

• River floodplains — especially the Skagit, Snoqualmie, Snohomish, Nisqually, and Chehalis river systems
• Stream banks and creek bottoms — even small seasonal creeks can support cottonwood stands
• Lake margins — the edges of lakes and reservoirs, particularly where soil stays moist
• Gravel bars and alluvial deposits — cottonwoods are pioneer species that colonize fresh sediment

They often grow in pure stands or mixed with red alder (Alnus rubra). In river valleys, you’ll frequently see a band of cottonwoods marking the floodplain edge — tall, broad-crowned trees that stand above the surrounding alder and willow.

How to Identify Black Cottonwood

Three features make cottonwood identification reliable year-round: leaves, bark, and overall stature. Even one of these is usually enough.

Leaves

Heart-shaped to triangular, 3–6 inches long. Glossy dark green on top, pale silvery-green underneath. Smooth edges with fine teeth. Sticky resinous buds in spring have a distinctive sweet balsam smell.

Bark

Young trees have smooth, yellowish-gray bark. Mature trees develop thick, deeply furrowed bark with flat-topped ridges. The bark gets darker and more rugged with age — distinctive even from a distance.

Stature

The largest deciduous tree in the PNW — up to 150 feet tall with a broad, open crown. In river bottoms, they tower over everything except old-growth conifers. Often the tallest deciduous tree in sight.

In winter and early spring before leaf-out, rely on bark texture and habitat. If you’re standing near a river looking at a tall, thick-barked deciduous tree with an open crown, it’s almost certainly a cottonwood. The resinous buds in late winter are another giveaway — break one open and smell the strong balsam fragrance.

Cottonwood vs. Similar Trees

In Western Washington, the main sources of confusion are:

• Red alder — Much smaller (40–60 ft), smooth gray-white bark with dark horizontal lenticels. Leaves are oval with serrated edges, not heart-shaped. Often grows alongside cottonwood.
• Bigleaf maple — Large but with deeply lobed (palm-shaped) leaves, completely different from cottonwood’s heart shape. Bark is brown and furrowed but less deeply than cottonwood.
• Oregon white oak — Found in drier prairies and south-facing slopes, not riparian habitat. Lobed leaves, gnarled form.

Once you’ve seen a mature cottonwood a few times, the combination of size, bark texture, and riparian habitat makes them unmistakable.

Mushrooms Associated with Cottonwood

Cottonwood supports some of the most sought-after spring mushrooms in the PNW. These species fruit on or near cottonwoods and are a major reason foragers learn to identify these trees.

Morels

Morchella

The main prize. Riparian morels fruit in cottonwood river bottoms during the early part of the season. Look in the leaf litter within drip line of mature trees, especially a few weeks after the first warm stretch in the early spring.

It’s complicated?
Choice Edible
Spring

Oyster Mushroom

Pleurotus populinus

Fruits on dead and dying cottonwood from spring through fall. P. populinus is the cottonwood-specific species — look for clusters on standing dead trees, fallen logs, and large branches.

Saprotrophic
Choice Edible
Spring–Fall

Verpa

Verpa bomemica

One of the earliest of the spring mushrooms. It’s ‘as edible’ as the true morels. Some forage for them while others simply enjoy finding and observing.

It’s complicated?
Edible
Spring

When to Hunt Near Cottonwoods

In Western Washington, cottonwood-associated mushrooms follow a rough seasonal pattern:

• March–April: Dryad’s saddle appears first, often before full leaf-out. Early oyster mushrooms on dead wood.
• April–May: Peak morel season in cottonwood bottoms. Watch for soil temperatures reaching 50°F and sustained warm rain events.
• May–June: Late morels at higher elevations. Oyster mushrooms continue through summer.
• Fall: Oyster mushrooms and chicken of the woods on cottonwood logs and standing dead trees.

The spring bud-break on cottonwoods is itself a phenological signal. When you see cottonwood buds swelling and the balsam scent fills the air, morel season is approaching. When leaves are about half-sized, conditions are often prime.