Just a Hop Makes The Difference

Two trees called Ironwood: American hornbeam (left), American hophornbeam (right) (photos by Kate St. John)

26 July 2021

Two trees in the Birch family (Betulaceae) are common in the Pittsburgh area but I’ve struggled with what to call them because they have the same names.

Both are called Ironwood because their wood is hard, close-grained, and very strong. Ironwood is a poor name choice, though. About 160 species around the world are called “ironwood”.

Their scientific names are different but their default common names are very similar: American hornbeam (Carpinus caroliniana) and American hophornbeam (Ostrya virginiana). Hornbeam refers to their hard, strong wood: horn (hard, bony structure) + beam (Old English for tree). Hop is the only difference.

Fortunately they are easy to tell apart in the field at any time of year. In the photo at top:

  • The bark of American hornbeam looks like sinewy muscles (top left).
  • American hophornbeam bark peels in narrow parallel strips (top right).

Both trees produce fruit enclosed in an involucre, a whorl or rosette of bracts surrounding the inflorescence. This is where “hop” comes in.

Both species with fruit and bark paired.

American hornbeam or blue beech, fruit and trunk (photos by Kate St. John)
American hophornbeam, fruit and trunk (photos by Kate St. John)

They differ by a hop.

p.s. Because of their similar names I sometimes call “hornbeam” by another common name: blue beech. More confusion!

(photos by Kate St. John)

2 thoughts on “Just a Hop Makes The Difference

  1. Just a hop, skip and a jump away from id. Thanks. I’ve got a bunch of those here in west of Pittsburgh

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