Equisetaceae - horsetail family
Species that grow without cultivation on Mount Desert Island

compiled by the
Champlain Project - P. O. Box 55 - Bass Harbor, Maine  04653

(updated 9 April 2017)

Equisetaceae - horsetail family
This family worldwide is composed of 15 species in one genus, Equisetum.

Mount Desert Island is home to 3 species in 1 genus. Click on a link below or scroll down for more information.
   Equisetum (3 species)
      Equisetum arvense - field horsetail (occasional1)
      Equisetum fluviatile - river horsetail (uncommon)
      Equisetum sylvaticum - wood horsetail (common)

Equisetum (horsetail)
Mount Desert Island's three species of horsetails can be distinguished from each other by their branching. Equisetum fluviatile is either unbranched or has short, seemingly random branches that are somewhat stubby and appear mutant. Equisetum arvense has a whorl of branches at each node (except on the fertile stems described below), as does E. sylvaticum. The branches of the latter, however, are themselves branched. Species of Equisetum that are unbranched are often called scouring-rushes.

Equisetum arvense (field horsetail) may be mistaken for two different species if one observes the stems in early April and then later in the season. This is because the stems are dimorphic; that is, they have two different forms. In early April (on Mount Desert Island) the fertile stems appear. They are flesh-colored and have no branches.
(click on an image to enlarge)

Equisetum fluviatile (river horsetail) grows in shallow freshwater, as in the image below taken at the south end of Bubble Pond.

(click on images to enlarge)

Equisetum sylvaticum (wood horsetail)

(click on images to enlarge)

   1Frequency designations are from the paper “Vascular flora of the Acadia National Park region, Maine” by Craig W. Greene, Linda L. Gregory, Glen H. Mittelhauser, Sally C. Rooney, and Jill E. Weber, published in the spring 2005 issue (vol. 107, No. 930) of Rhodora: Journal of the New England Botanical Club.