Plant Data Sheet
Sitka Alder / Slide Alder - Alnus sinuata, syn. Alnus viridis ssp. sinuata
Native to a large area, from the
Usually found above 3,000 ft (900 m) elevation, although it
also grows in the snowy coastal tundra of
Most commonly found in Avalanche chutes (fairly common)
where it forms dense thickets, but also found along cool mountain streams in
“Scattered thickets of
alder are normally located on cool moist sites, on north-facing slopes, or Sitka
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
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) Sitka
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 .
Sow in moist mineral soil on surface (spring) or barley covered (fall). (ref 5.)
Recommended seed storage conditions
Cool, dry place in acid free envelope.
Stem cuttings of
Soil or medium requirements
Prefers a heavy moist soil.
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
Western Washingtonfound that it takes 3 to 4 years for 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). Sitka
Data compiled by Christer Lundstrom