Alnus
alder
4 species
3 subspecies and varieties
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Alnus incanamountain alder
Distribution: Occurring east of the Cascades crest in Washington; Alaska south to New Mexico, also in the north-central and northeastern region of North America.
Habitat: Moist places, streamside, low to high elevations.
Origin: Native
Flowers: March-May
ssp. tenuifolia – mountain alder
Alnus rhombifoliaCalifornia alder, white alder
Distribution: Chiefly east of the Cascades crest in Washington; Washington south to California and Nevada, east to Idaho.
Habitat: Near streams at low elevations.
Origin: Native
Flowers: January-April
Alnus rubraOregon alder, red alder
Distribution: Occurring chiefly west of the Cascades crest in Washington; Alaska south to California, disjunct to the east in northern Idaho.
Habitat: Moist areas at low elevations.
Origin: Native
Flowers: March-April
Alnus viridisgreen alder, mountain alder
Distribution: Widely distributed throughout the mountainous areas of Washington; Alaska south to California, east across the northern half of North America to the Atlantic Coast.
Habitat: Moist areas, low to high elevations.
Origin: Native
Flowers: May-July
ssp. fruticosa – Siberian alder
ssp. sinuata – mountain alder, Sitka alder