Speckled Alder

Speckled Alder

Alnus incana ssp. rugosa (Du Roi) R.T. Clausen

Description

Speckled alder is in the birch family (Betulaceae) and is a subspecies separated from the introduced gray alder and native thin-leaf alder ¹.  It is a shrub or small tree that grows to 30 feet ².  The red, brown or gray bark is thin and smooth with conspicuous white lenticels that give it the common name ².  The oval leaves are up to 4 inches long with doubly serrate margins and straight, parallel veins from midrib to margin ².  Male and female flowers are in catkins.  The male catkins are up to 2.5 inches long at the end of the winter branches.  The female catkins are 3/4 inch cone-like structures that may persist after shedding seeds ².

Bark with lenticels of speckled alder.  S. Muller, Maryland Biodiversity Project ³

Leaves of speckled alder. S. Muller, Maryland Biodiversity Project ³

Gray Alder in Allegany Co., Maryland (10/4/2019).

Previous year’s brown female catkins and current years green male catkins of speckled alder.  M. Evans, Maryland Biodiversity Project ³

Distribution

Speckled alder crosses two-thirds of Canada to its eastern seaboard and south to Virginia and Illinois.  It is found in damp soils and along stream banks.  In Maryland it is only in the mountains of Garrett and Allegheny Counties ³

Natural range of speckled alder.  USDA, Forest Service ¹

Wildlife Importance

Speckled alder provides habitats for moose, rabbits and deer.  In addition they provide food for beavers and the construction of lodges and dams². The seeds provide food for birds such as redpolls and grouse ².

Economic Importance

Speckled alder has no commercial importance.  It is used horticulturally in wet areas and helps with control of erosion ².

Threats

Few insects or diseases affect speckled alder ².  It is capable of res-touting from low-intensity fire, but can be killed by high-intensity fire ².

Interesting Facts

  • Indigenous People used ground up bumblebees and alder root for women in childbirth ².
  • The roots of speckled alder have nodules that contain nitrogen-fixing bacteria which enhance the soil surrounding them ².

References

  1. USDA, Forest Service–Fire Effects Information System: Alnus incana
  2. USDA NRCS Plant Guide: Speckled alder
  3. Maryland Biodiversity Project:  Gray alder

Contributed by J. Hull

Towson University Glen Arboretum

Towson University

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