Plant Data Sheet


Sitka Alder / Slide Alder   -    Alnus sinuata, syn. Alnus viridis ssp. sinuata



Native to a large area, from the Yukon and western and southern Alaska southward to northern California and eastward to southwestern Alberta and western Montana, also northeastern Oregon.  (ref. 1)


Climate, elevation

Usually found above 3,000 ft (900 m) elevation, although it also grows in the snowy coastal tundra of Alaska. (ref. 1)


Local occurrence

Most commonly found in Avalanche chutes (fairly common) where it forms dense thickets, but also found along cool mountain streams in Oregon and Washington.


Habitat preferences

“Scattered thickets of Sitka alder are normally located on cool moist sites, on north-facing slopes, or
other shady aspects…  It is a vigorous invader of talus slopes, avalanche chutes, seepage areas, and high elevation mountain swales.” (ref 2)





Plant strategy type/successional stage

Generally considered a pioneer or early seral stage.  Its ability to fix nitrogen allows it to invade soils with low fertility, such as those recently exposed by glaciers or avalanches. (ref 1, 2).  “On steep terrain in heavy snowpack areas, recurrent avalanches are partially responsible for the creationand maintenance of Sitka alder communities.  The soils exposed by avalanches provide an ideal seedbed for Sitka alder seeds.  Once established, its resilient wood, bowed growth form, and ability to resprout if stems are broken allow Sitka alder to withstand repeated avalanche destruction, which would normally kill other plants.” (ref. 2)


Associated species

Acer glabrum, A. circinatum, Sambucus spp, Salix spp, Ribes lacustre, Sorbus spp.  Menziesia ferruginea, Montia cordifolia, M. sirbirica, Senecio triangularis, Asarum caudatum, Athyrium felix-femina, Clintonia unifloria, arnica latifolia, Pyrola secunda, viola glabella, Urtica dioica, Mertensa paniculata and Pterdidium aquilinum.


May be collected as: seed


Collection restrictions or guidelines

Seeds are dispersed during the fall .


Seed germination

Sow in moist mineral soil on surface (spring) or barley covered (fall). (ref 5.)


Seed life



Recommended seed storage conditions

Cool, dry place in acid free envelope.


Propagation recommendations

Stem cuttings of Sitka alder seldom, if ever, produce roots. (ref. 2)


Soil or medium requirements

Prefers a heavy moist soil.


Installation form


Recommended planting density

Space at least 1m apart as they usually form multi-stemmed shrubs.


Care requirements after installed

Keep soil moist.


Normal rate of growth or spread; lifespan

“Studies in Western Washington found that it takes 3 to 4 years for Sitka alder seedlings to reach 3 feet (1 m) in height, and 10 years to reach 13 feet(4 m) Seedlings take 4 to 7 years to start producing seed.” (ref 2).  Plant lifespan “long” (ref 3).


Sources cited











Data compiled by Christer Lundstrom