Alnus incana ssp. tenuifolia (syn. Alnus tenuifolia) Betulaceae
Thinleaf Alder, Mountain Alder
AL-nus in-KAH-na ten-U-i-fol-i-a
- Broadleaf deciduous, thicket forming multistemmed shrub or small tree, to 20-40 ft (6-12 m), rounded form. The bark is thin, smooth, and green-gray, grayish-brown, or reddish-brown; buds stalked or sessile. Leaves alternate, simple, broadly elliptic or ovate-oblong, mostly 3-7 cm long, dull green on both sides, with doubly dentate margins, thinner and smoother than Sitka Alder.
- Sun part shade.
- Hardy to USDA Zone 5 Widely distributed, its native range is from central Alaska and the Yukon Territory,
southeast to western Saskatchewan and British Columbia, and south throughout the Mountain States to New
Mexico and California. Considered the most common alder of the Rocky Mountains, the Sierra
Nevada, and the east side of the Cascades. It is often found near water, and its presence is
an indication of streams, springs, or seeps. Thinleaf Alder resembles, but is larger than,
Speckled Alder (A. incana ssp. rugosa), with which it hybridizes where their ranges overlap.
- Thinleaf Alder is part of a very large circumpolar alder group (Alnus incana, Gray Alder) which
is distributed across much of North America and Europe. Alnus incana has been separated
into three subspecies, the Thinleaf Alder (A. i. ssp. tenuifolia), Speckled Alder (A. i.
ssp. rugosa), both native to North America, and the third, A. i. ssp. incana,
encompassing plants of the old world. This classification system is not fully accepted.
- incana: white, a reference to the underside of leaves.
- Oregon State Univ. campus: south of Peavy Hall, native plants area.