Alnus incana subsp. rugosa
Common name: 
Speckled Alder
AL-nus in-KAH-na ru-GOS-a
Alnus rugosa
Native to (or naturalized in) Oregon: 
  • Deciduous shrub or small tree, to 20 ft (6 m) tall and about 16 ft (5 m) wide, branches smooth with horizontally striped lenticels.  Leaves alternate, simple, ovate, 5-10 cm long and 3-6 cm wide, margin serrate with teeth of two sizes, tip pointed (acute or obtuse), base rounded or wedge-shaped, 9-12 nearly straight parallel veins on each side, upper surface dark green and somewhat wrinkled (rugose), lower surface light green and smooth or with hairs on veins; petiole 1-3cm long.  Flowers male and female, male (staminate) catkins 4-9 cm long, female (pistillate) catkins 2-5 mm long.  Fruit, cone-like, 13-16 mm long and about 10 mm wide, ovoid, short stalked.
  • Sun and shade.  Best in a moist soil high in organic matter.
  • Hardy to USDA Zone 2         Its native range is eastern North America, it is most common in the Great Lakes and the St. Lawrence Seaway areas, including east-cental Canada, the Maritime Provinces, it also appears sporadically throughout all the remaining Canadian provinces and south along the Appalachian Mountains to West Virginia and Maryland.  It is frequently found in stream and lake borders, bogs, and nutrient-rich swamp communities.
  • Speckled 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. incana subsp. tenuifolia), Speckled Alder (A. incana subsp. rugosa), both native to North America, and the third, A. incana subsp. incana, encompassing plants of the old world.  This classification system is not fully accepted.
  • From Flora of North America
    • ​Alnus incana subsp. rugosa (Speckled Alder):  Leaf blade thick, major teeth sharp; large shrubs
    • Alnus incana subsp. tenuifolia (Thinleaf Alder): Leaf blade thin and papery, secondary teeth rounded or blunt; large shrubs or small trees
  • incana: quite gray, a reference to the underside of leaves.  rugosa: wrinkled, apparently a reference to the network of sunken veins prominent on the lower leaf surface.
Click image to enlarge
  • plant habit

    plant habit

  • leaves


  • developing seed cones

    developing seed cones

  • trunk, bark

    trunk, bark