: Alnus alnus
: European alder, European black alder
: Capable of displacing native vegetation; fixes nitrogen; has been planted on highly disturbed or infertile sites and for windbreaks; vulnerable to tent caterpillar.
: Deciduous; medium tree; ranging from 9-18 m (30-60 ft) in height and 25-38 cm (10-15 in) in diameter; narrow pyramidal shape when young, becoming more irregular with age.
: Simple, alternate, broadly rounded to truncate or notched at the apex, 5-13 cm (2-5 in) long and 5-10 cm (2-4 in) wide, toothed leaf margin, young leaves sticky to the touch, fall leaves green or brown in color.
: Dark green-brown, smooth or rough, speckled with short lenticels, bark with prominent warty strips; buds stalked.
: Male and female flowers in separate structures, male flowers borne on long narrow catkins, female flowers borne in small woody structures resembling pinecones; bloom March through May.
Fruit and seeds
: Small, woody, pinecone-like structure borne on long, narrow stalks; seeds are small and narrowly winged.
: Native to Eurasia and North Africa; prefers full sun and wet soil but tolerant of drier soil and a range of pH conditions; found along rivers, in wetlands and moist forests.
: By seed and spreading roots.
: Native speckled alder (Alnus rugosa
) has leaves with a distinct (acute) tip; usually shrubbier than A. glutinosa
Monitoring and rapid response
: Monitor pond, river and wetland margins; distinguishable year-round by its rounded leaves, catkins, cones and stalked vegetative buds. Begin control efforts in highest quality areas. Hand pull seedlings and remove mature trees that provide a source of seed. Cutting, girdling, and mowing are ineffective unless cut stumps are treated with herbicide to prevent resprouting.
: The Michigan Natural Features Inventory
(MNFI) has partnered with MISIN to provide the information in this fact sheet. Species images and/or information were used with permission from "A Field Identification Guide to Invasive Plants in Michigan's Natural Communities
" and "A Field Guide to Invasive Plants of Aquatic and Wetland Habitats for Michigan