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Note large colonies

Fronds with leaflets

Osmunda claytoniana

Common Name: Interrupted Fern
Family: Osmundaceae

Description:  This annual fern is named for its brown fertile leaflets which interrupt the larger green sterile leaflets on larger fronds.  
There are a combination of two leaflets on each frond. There are small brown fertile leaflets and larger green sterile leaflets. The larger green leaflets have distinctive rounded edges.
They are spores located on brown fertile leaflets
Stem:  The petioles are covered in wooly hairs which decrease with age.
Branching Pattern:
   symmetric clump
Height:  Fronds can be 2-4 feet long
Conditions/Habitat/Kind of Forest:  It can grown in semi shade to no shade, but it must have moist soil. It is found in woods, roadsides, swamps and low prairies. 
Known Wildlife Interactions: Pollinated by insects
Range:  North America, Newfoundland south to Florida. Naturalized in Ireland. Also found in east Asia
Conservation Status-US/ World Wide:  Not threatened in U.S. or globally.
Uses (Human): No known usage.


Connecticut Wildflowers.  January 20, 2006.  Connecticut Botanical Society.  Accessed:  January 20, 2006. <>

Plants for a Future.  June 2004.  Accessed: January 20, 2006.  <>

The Pennsylvania Flora Project.  Botany Department, Morris Arboretum of the University of Pennsylvania.  Accessed:  January 20, 2006. <>

Chadde, Steve W. A Great Lakes Wetland Flora. Pocketflora Press. 2002. pg.67

IUCN Red List of Threatened Species <>

This page was created by: A Coiro, Muhlenberg College
Photos by: L. Rosenberg, edited by N. Smith
Last updated 04/25/06