Sitka Alder

Sitka alder (Alnus sinuata, Betulaceae; syn. A. alnobetula subsp. sinuata) is a fast-growing native deciduous shrub or small tree found from Alaska to California and inland to Montana and Wyoming, as well as parts of temperate Asia including Kamchatka and Sakhalin. It is recognized by its sinuate (wavy-toothed) leaves and occurs naturally in moist woods, along stream banks, at pond margins, and on open montane slopes near timberline.

Sitka alder grows in sun to part shade on wet-tolerant soils across a wide pH range (4.5 to 8.5) with high water needs, hardy in Zones 2a to 9b. It is a nitrogen-fixing species, adding approximately 20 kilograms of nitrogen per acre annually to the soil. Disease associations (11 documented) include Armillaria root rot, canker and stem diseases, drippy dieback, and powdery mildew. Pest associations include aphids, fall webworm, flea beetle, and tent caterpillar. No cultivars are in the trade.