Hazel Alder

Hazel Alder

Alnus serrulata (Aiton) Willd.

Description

Hazel alder, also called brookside alder 6, tag alder or smooth alder ¹, is a member of the birch family (Betulaceae).   It is a small tree, seldom more than 20  tall. ² It has smooth bark (hence its other common name) and  inconspicuous lenticels or pores. ¹  Leaves are oval, 2 to 4 inches long  by 1.5 to 2.5 inches wide, with serrate or double-senate margins.  Flowers are borne in catkins with separate male and female flowers on the same tree.  The male catkins are 2 to 4 inches long, yellow and hang down in clusters of 2 to 5. ²  Female catkins are  less than 1 inch long, red and are erect. ²  Fruits are cone-like, brown structures about 1 inch long that persist into the winter and bear numerous winged seeds. ¹

Three rod-shaped male catkins hang down to the right from a gray and red branch that looks slightly fuzzy and dusted. The flowers are a pale orange-yellow with touches of purplish-red buds. To the left of the male catkins are small purplish-red female catkins that look like thick nubs with sharp hairs all around it.

Erect red female catkins and drooping yellow male catkins of hazel alder in spring.  Maryland Biodiversity Project, S. Muller ³

Aged, dark brown female fruits of a Hazel Adler hanging from a leafy branch. Blurred branches of a Hazel Adler are behind it.
Dark brown, aged female fruits of a Hazel Alder hang from their branch with three leaves sprouted on an adjacent branch, with blurred Hazel Alder branches visible in the background.

Female fruits of previous year.  Maryland Biodiversity Project,  P. Martin ³

Distribution

Hazel alder is distributed from the Saint Laurence River system to the Great Lakes and South to Texas and Florida.  It is found in wetlands. 4  In Maryland hazel alder is found throughout the state in moist areas along streams and flood plains. ³

A gray and white map of the eastern half of the United States and southeastern Canada. The native range of Alnus serrulata is shown in a bright neon green, and encompasses almost all of the southeastern United States. The range excludes most of Florida outside of the Florida panhandle, and much of the Arkansas/Louisiana border with Mississippi and Tennessee, but picks up again through most of western Arkansas, southeastern Missouri, and northwestern Louisiana. The range extends up through the mid-Atlantic states, including much of southern Pennsylvania, eastern New York, and all of Connecticut, Massachusetts and Rhode Island. Small parts of southern Vermont, southern New Hampshire, and southern Maine are also included, as well as the southern most part of Nova Scotia.

Native range of hazel alder.  Wikimedia Commons 5

Wildlife Importance

Numerous insects feed upon hazel alder including the flea beetle, leaf beetle, and leaf hoppers. 6 Numerous birds consume seeds and/or buds including American Wigen, Red-breasted Grosbeak, and Pine Siskin. 6 American beaver utilize the wood and bark for food and stems for dam construction. 6

Economic Importance

Hazel alder is used for stream bank stabilization. 7

Threats

Hazel alder is susceptible to canker and powdery mildew. ¹

Interesting Facts

  • Root nodules of hazel alder fix nitrogen ², one of only a new non-luminous plants that have this ability.
  • Native Americans had numerous uses of hazel alder including to reduce the pain of childbirth, for coughs and fevers and to lower blood pressure. 4
  • In earlier works Alnus serrulata was mistakenly called Alnus rugosa, a name that has unfortunately persisted. 4

References

  1. North Carolina Extension:  Alnus serrulata
  2. Missouri Botanical Gardens:  Alnus serrulata
  3. Maryland Biodiversity Project; Smooth alder
  4. Flora of North America:  Alnus serrulata
  5. Wikimedia Commons: Alnus serrulata
  6. Illinois Wildflowers:  Brookside alder
  7. Plants for a Future: Alnus serrulata

Contributed by J. Hull

Towson University Glen Arboretum

 

Towson University