When does red alder bloom?

Red alder produces drooping male catkins and small female cones from March through May, often opening before the leaves fully unfold.

How much water does red alder need?

Red alder does best in consistently moist to wet soil and is commonly found along streambanks, floodplains, and other high-moisture sites.

What pollinators are attracted to red alder?

Bees and moths visit red alder catkins in early spring, taking advantage of the pollen available before many other plants have flowered.

How large does red alder get and where does it grow best?

Red alder is a fast-growing deciduous tree that can reach roughly 40 to 100 feet tall. It grows best in moist, well-drained lowland sites and disturbed areas with full sun to partial shade.

Can red alder tolerate shady conditions?

Red alder grows most vigorously in full sun to part sun, though young trees can tolerate part shade before the canopy closes in.

Is Red Alder toxic to livestock?

The USDA PLANTS Database does not flag Red Alder as toxic to livestock.

Is Red Alder HOA-friendly?

Red Alder takes more care to look intentional in a front yard. Consider it for backyard or mid-zone beds rather than the street edge.

Red Alder

Name: Pollinator Patch
Author: Pollinator Patch

Alnus rubra

Last reviewed: September 2026

Alnus rubra is a fast-growing deciduous tree found along streambanks and moist lowland forests in the Pacific Northwest, with reddish catkins blooming from March through May.

Toxicity unknown

Red Alder (Alnus rubra) is not listed by the ASPCA Animal Poison Control Center (opens in new tab) or the other sources we check, so we have no verdict for it either way. Absence from those lists is not a clearance. If your pet shows symptoms after eating any plant, call the ASPCA at (888) 426-4435.

The USDA PLANTS Database (opens in new tab) does not flag Red Alder as toxic to livestock.

Light

part sun

Water

high

Size

240"–800" H × 180"–480" W

Bloom

Mar, Apr, May

Native to

CA, ID, MT, OR and 1 more states

Pollinators

bees, moths

Before you buy

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Browse plants for this ecoregion

Coast Range Puget Lowland Marine West Coast Forest Northwestern Forested Mountains Central California Foothills and Coastal Mountains North American Deserts Southern California/Northern Baja Coast

Red alder is a fast-growing deciduous tree that can reach 20-65 feet tall. It thrives in moist conditions and produces catkins in spring, with serrated green leaves that turn yellow in fall. This nitrogen-fixing tree naturally improves soil quality but requires consistent moisture to establish well.

Growing Red Alder

Grow Red Alder in part sun and high water. Mature plants reach 240 to 800 inches tall and spread 180 to 480 inches wide. Expect high maintenance to keep it looking intentional in a front yard.

In an HOA neighborhood

Red Alder takes more care to keep looking intentional in a front yard. Maintenance level: high. Consider it for backyard or mid-zone beds rather than the street edge.

Works well in: backyard only.

Extremely large mature size inappropriate for most residential lots
High water requirements may conflict with xeriscape preferences
Fast growth can appear uncontrolled without regular pruning

Wildlife value

Host plant for white-lined sphinx moth.

Supports bees and moths during its spring bloom period with abundant catkins. The tree also provides nesting habitat for birds and its seeds feed various wildlife species.

Common questions

When does red alder bloom?: Red alder produces drooping male catkins and small female cones from March through May, often opening before the leaves fully unfold.
How much water does red alder need?: Red alder does best in consistently moist to wet soil and is commonly found along streambanks, floodplains, and other high-moisture sites.
What pollinators are attracted to red alder?: Bees and moths visit red alder catkins in early spring, taking advantage of the pollen available before many other plants have flowered.
How large does red alder get and where does it grow best?: Red alder is a fast-growing deciduous tree that can reach roughly 40 to 100 feet tall. It grows best in moist, well-drained lowland sites and disturbed areas with full sun to partial shade.
Can red alder tolerate shady conditions?: Red alder grows most vigorously in full sun to part sun, though young trees can tolerate part shade before the canopy closes in.
Is Red Alder toxic to livestock?: The USDA PLANTS Database does not flag Red Alder as toxic to livestock.
Is Red Alder HOA-friendly?: Red Alder takes more care to look intentional in a front yard. Consider it for backyard or mid-zone beds rather than the street edge.

These answers were drafted with an AI model from this plant's data. Verify care details with a local expert.

Native range data from vouchered herbarium specimen records and regional native plant society lists. Pollinator and host plant associations compiled from GBIF, iNaturalist, and published ecological literature.

If something looks wrong

Common plant problems, and what to check first

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See all plant problem guides

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