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When robust and well-developed this is an easily recognized species, growing in decidedly wet habitats with stems 40-80 cm tall, conspicuous branches (especially near the middle of stem) and a terminal strobilus. The form is highly variable however and while you may find a local population with numerous fertile stems on occasion, in my experience in Wisconsin, fertile stems are relatively few in most years.
E. palustre is roughly similar to Equisetum arvense, a much more common and widespread species in this area. If the plants are fertile they are easily distinguished, since E. arvense has separate, non-green fertile stems and E. palustre strobili are borne atop green stems otherwise similar in form to sterile stems. When E. palustre is sterile and branches are well-devloped, it can be distinguished by the first internode of the lower branches being shorter than the adjacent sheath of the main stem (image), and by sheaths that are clearly longer than broad. The first internode of the lower branches of E. arvense is clearly longer than the adjacent sheath of the stem and sheaths are about as long as broad.
On occasion the stems of E. palustre may lack branches and might then be confused with E. fluviatile, which however, can be easily recognized by the very large central opening in the stems, often comprising about 90% of the stem diameter. The central opening in stems of E. palustre is small, often about 1/3 of the stem diameter. Also, the stem sheaths of E. palustre are clearly longer than broad and bear 5-10 teeth. E. fluviatile sheaths are about as broad as long and bear 12 or more teeth.
E. palustre is a northern species, ranging from Alaska across Canada and south to New England, Minnesota and northern California. In Wisconsin, most locations are from the northern counties. |
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