Northern Ontario Plant Database
Alnus incana subsp. rugosa (DuRoi) R.T.Clausen
En: speckled alder, tag alder, swamp alder, eastern river alder, aulne blanc rugueux
Betulaceae (Birch Family)
General: A tall deciduous shrub, 5-9 m tall. Young branches mostly smooth (glabrous); buds stalked, dull, ellipsoid and blunt-tipped, 3-7 mm long; bud scales 2, valvate, reddish- to purplish-brown. The bark is brown to dark gray and marked with prominent, whitish, horizontal lenticels.
Nomenclatural Notes: Synonym: Alnus rugosa (DuRoi) Spreng.
Leaves: Alternate, simple, pinnately-veined, petiolate. Leaf blades broadly elliptic to ovate, 4-11 cm long, dark green above, smooth to barely sticky (resinous), paler and glabrous to hairy beneath; base broadly cuneate to rounded; apex pointed (acute); the margins often shallowly lobed, jagged, or wavy and double-toothed (biserrate). Veins in 10 or more pairs, hairy, the small cross-veins meeting and forming ladder-like connections between the secondary veins, clearly visible on the lower leaf surface.
Flowers: Unisexual, arranged in terminal catkins (aments); plants monoecious, with male and female catkins borne on the same plant and emerging well before the leaves. Male catkins elongate, 2-7 cm long, in clusters of 2-4; female catkins small, ovoid, in clusters of 2-6, borne a short distance behind the male catkins on the same branch; both lacking bud scales (naked). Female catkins becoming cone-like and woody as the fruits develop.
Fruit: Very small samaras, 2-2.5 mm long, with narrow wings, borne in sessile or short-stalked, persistent ovoid woody cones, 1-1.7 cm long
Habitat and Range: Stream margins, wet shores and meadows, peatlands, swamps, and wet ditches; often forming dense alder thickets adjacent to small streams. Speckled alder is a boreal and north-temperate subspecies of eastern North America, occurring throughout Ontario; its range extends from Newfoundland and Labrador westward to Saskatchewan. Another subspecies, the thinleaf alder, Alnus incana subsp. tenuifolia (Nutt.) Breitung, occurs in western North America. The typical subspecies, A. incana subsp. incana (L.) Moench, is restricted to northern Europe.
Similar Species: The mountain alder, Alnus viridis subsp. crispa, grows in drier ground than the tag alder. Mountain alder can be distinguished clearly by several characters, including its nearly sessile, pointed buds, more regularly and finely toothed (serrulate) leaf margins, and cross veins between the secondary veins that do not meet. Also, female catkins of mountain alder are contained within winter buds, so are not visible until the leaves emerge. In fruit, the female catkins are borne on long stalks.
The speckled alder webpage from the Trees of Wisconsin website. Click on the smaller images to view larger, more detailed photos.
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