Speckled Alder


(Alnus incana subsp. rugosa)

Speckled Alder
Mara McHaffie, no rights reserved (CC0)
Speckled Alder
© Olivia Tittaferrante, some rights reserved (CC-BY-NC)
Speckled Alder
© Serguei Ponomarenko, some rights reserved (CC-BY-NC)
Speckled Alder
© greenari, some rights reserved (CC-BY-NC)

Speckled alder is a fast growing Shrub to small tree often forming thickets. Three subspecies of Alnus incana span across the Northern Hemisphere and the subspecies rugosa is native to central and eastern Canada. The tree thrives in nutrient poor, sandy, rocky or mucky soil where adequate moisture is present. It dominates on riverbanks, swamps, bogs, and wetlands; tolerates continuous flooding but less so than willow. Speckled alder has a symbiotic relationship with soil actinomycetes that can fix nitrogen from the air, helping to enrich the soil around it.

The name 'speckled' comes from white, warty lenticels present on the bark. Leaves appear wrinkled, being sunken at the veins, hence the name rugosa. Leaf undersides are red and hairy; margins are doubly serrated. Purplish brown male catkins and green female catkins appear March to early April, followed by fruiting bodies resembling pine cones. The winged seeds embedded within them attract birds. This restorative, native tree has no serious insect or disease problems except canker, which can possibly be severe.


Fire Effects Information System (FEIS). (n.d.). Alnus incana. Retrieved from https://www.fs.fed.us/database/feis/plants/tree/alninc/all.html

Missouri Botanical Garden. (n.d.). Alnus incana subsp. Rugosa. Retrieved from https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=277838&isprofile=0&

Natural resources Conservation Service. (n.d.). Alnus incana (L.) Moench ssp. rugosa (Du Roi) R.T. speckled alder. Retrieved from https://plants.usda.gov/core/profile?symbol=ALINR

Tree Canada. (n.d.). Speckled alder (Alnus incana ssp. rugosa). Retrieved from https://treecanada.ca/resources/trees-of-canada/speckled-alder-alnus-incana-ssp-rugosa/