Alnus rubra
Red alder, Red Alder
(c) Casey H. Richart, some rights reserved (CC BY) · licence
Family: Betulaceae · Type: Tree · Native
Alnus rubra (Red alder) is a native California tree in the Betulaceae family, recognized by clearly distinguished by rolled leaf margins and rusty-hairy leaf undersides.
Red alder is a native tree found in northern coastal California, western Klamath Range, northern coastal Redwood, central coastal, and San Francisco Bay areas in wet places, especially after logging, at elevations below 1,000 meters. Flowering from February to March, this tree produces small, inconspicuous flowers in catkins. Growing up to 25 meters tall with a trunk of moderate width, it has a distinctive bark and branching structure. Its leaves are thick with rounded to tapered bases, acute tips, and tightly rolled margins, appearing gray-green on top with indented midribs and major veins, while the underside is similarly gray-green and covered with rusty hairs or rusty sessile glands. In disturbed wet areas, red alder plays a critical role in forest regeneration and soil stabilization.
Identification and appearance
Key characters: 5 sympatric species; clearly distinguished by rolled leaf margins and rusty-hairy leaf undersides
Habitat and range
Habitat: Wet places, especially after logging
Elevation: < 1000 m
California counties: Humboldt, Marin, Mendocino, Del Norte, Santa Cruz, Sonoma, Alameda, Contra Costa, San Mateo, Monterey, Santa Clara, Shasta, San Luis Obispo, Trinity, Siskiyou
Outside California: to southern Alaska, Idaho
Bloom period
Alnus rubra blooms Feb-Mar.
How to tell it apart
vs Corylus: Alnus has tiny winged seeds from persistent woody cones; Corylus has large nuts in papery husks.; vs Populus: Alnus has woody persistent cone-like catkins; Populus has fluffy cottony seeds from capsules.; vs Quercus: Alnus has woody cone-like catkins and toothed leaves; Quercus has acorns in caps and lobed leaves.; vs Betula: Alnus has woody cones that persist after seeds drop; Betula catkins disintegrate completely, releasing papery scales with seeds.; vs Ulmus: Alnus has woody cone-like catkins; Ulmus has flat, round, papery winged fruits.
Frequently asked questions
Is Alnus rubra native to California?
Yes. Alnus rubra is native to California (recorded as native).
When does Alnus rubra bloom?
Alnus rubra blooms Feb-Mar.
Where in California does Alnus rubra grow?
Alnus rubra occurs in Humboldt, Marin, Mendocino, Del Norte, Santa Cruz, Sonoma, Alameda, Contra Costa and other counties, at elevations of < 1000 m.
What plant family does Alnus rubra belong to?
Alnus rubra is in the Betulaceae family, genus Alnus.
What habitat does Alnus rubra grow in?
Alnus rubra grows in Wet places, especially after logging.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.