Northern Ontario Plant Database
Alnus alnobetula subsp. crispa (Aiton) Raus
En: mountain alder, American green alder, green alder
Betulaceae (Birch Family)
General: A deciduous shrub to 3 m tall. Young branches smooth (glabrous) to slightly hairy, becoming smooth (glabrate), somewhat resinous; buds nearly sessile, shiny, reddish-brown, ovate, and pointed (acute) at the tip; bud scales overlapping (imbricate), 4–6.
Leaves: Alternate, simple, pinnately-veined, petiolate. Leaf blades broadly elliptic to ovate, 3–11 cm long, dark green above, somewhat glutinous and glabrous to hairy beneath, often with just the veins slightly hairy; base rounded to cordate; apex pointed (acute); and margins irregularly and finely toothed (serrulate). Veins in 7–9 or more pairs, hairy, the small cross-veins not meeting.
Flowers: Unisexual, arranged in catkins (aments), with male and female catkins borne on the same plant (plants monoecious). Male catkins elongate, terminal, lacking bud scales. Female catkins small, 1–2 cm long, enclosed within lateral buds during winter then emerging with the leaves in early spring, becoming cone-like and woody as the fruits develop.
Fruit: Very small samaras, 2–2.5 mm long, with broad lateral wings, borne in long-stalked persistent ovoid woody cones.
Habitat and Range: Rocky slopes, shores, bogs, cold woods, and disturbed areas. A boreal North American subspecies, occurring throughout Ontario. Mountain alder ranges from Newfoundland and Labrador westward to Alberta and the Northwest Territories.
Internet Images: The Alnus viridis subsp. crispa webpage from the Trees of Wisconsin website. Click on the smaller images to view larger, more detailed photos.
Similar Species: The speckled or tag alder, Alnus incana subsp. rugosa, is similar to mountain alder, but easily distinguished from it by several characters. In speckled alder, the buds are stalked, dull, and blunt at the tip; leaves are more coarsely toothed and the cross veins join in a ladder-like fashion between secondary veins; and woody seed cones are sessile or short-stalked. Also, female catkins of speckled alder are not contained within winter buds, they are borne naked, a short distance behind the male catkins and on the same branchlets.
Compare the images of mountain alder (above) to those of speckled alder, also from the Trees of Wisconsin website.
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