Aquatic and Wetland Vascular Plants of the Northern Great Plains

11. Betulaceae, the Birch Family

1. Alnus P. Mill. -- Alder

1. Alnus incana (L.) Moench -- Speckled alder

Shrub to 5 m tall; twigs reddish-brown, pruinose, mostly with conspicuous, light-colored lenticels. Leaves dark green and glabrous above, paler and pubescent on the veins beneath, ovate to elliptic, 5-14 cm long, 3-7 cm wide, serrate and shallowly lobed; petioles 1-2.5 cm long; stipules caducous, irregularly lanceolate, 6-15 mm long, 1.5-5 mm wide, variably pubescent. Catkins in terminal clusters of 3-several; male catkins short-peduncled, elongate, 4-9 cm long, 7-9 mm thick; female catkins sessile, cylindric, in flower 5-6 mm long, 2-2.5 mm thick, the scales unlobed, in fruit becoming conelike, 13-18 mm long, 8-13 mm thick. Nutlets flat, slightly winged, obovate, 3 mm long, about as wide. Flowering May, fruiting Aug--Sep. Swampy areas and stream banks; occasional in e ND; (Newf. to AK, s to MD, OH, n IN, MN, e ND, NM, AZ and CA; also Eurasia). A. rugosa (Du Roi) Spreng.

North American A. incana is designated subsp. rugosa (Du Roi) R. T. Clausen.


Twig of Alnus incana, showing conelike female catkins below and a terminal cluster of male catkins.

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