Red Alder
Alnus rubra
Last reviewed: June 2026
Red Alder is a fast-growing deciduous tree native to the Pacific Northwest from California to Montana. It blooms March through May and thrives in moist soils along streams and disturbed areas.
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
Browse plants for this ecoregion
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
- Where does Red Alder naturally grow?
- Red Alder is native to the western United States, including California, Idaho, Montana, Oregon, and Washington. It typically grows in moist areas along streams, rivers, and recently disturbed sites.
- When does Red Alder bloom?
- Red Alder blooms from March through May, producing small catkins before the leaves emerge in spring.
- What pollinators visit Red Alder?
- Red Alder attracts various pollinators including bees and moths. The tree is wind-pollinated but its flowers also provide nectar and pollen for insects.
- What growing conditions does Red Alder prefer?
- Red Alder thrives in moist to wet soils and can tolerate full sun to partial shade. It grows rapidly in disturbed soils and is often one of the first trees to colonize cleared areas.
- 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.
Native range data from the USDA PLANTS Database and regional native plant society lists. Pollinator and host plant associations compiled from GBIF, iNaturalist, and published ecological literature.
Ready to grow Red Alder? Add it to your garden in Pollinator Patch to track it and get season-by-season care guidance.