Equisetum fluviatile L.
Equisetum fluviatile L. var. limosum (L.) Gilbert
Equisetum limosum L.
Water horsetail, swamp horsetail
Water horsetail is the smoothest of the horsetails. Fluviatile is Latin for “pertaining to rivers,” and this horsetail is common in wet, shallow, marshy areas. Like other horsetails, water horsetails have a remarkably high silica content, making them abrasive enough for scouring or sanding.
Plants: Water horsetails occur in dense colonies, where they may be unbranched or multiply branched. Fertile and sterile stems look the same. They are 14-46" (35-116 cm) tall, with dark green stems ¹/₁₆-¼" (2-8 mm) in diameter. If branches are present, they are less than 3" (7.6 cm) long, with 8 or fewer nodes. Each segment boundary is ringed by a series of tiny, black-tipped scale leaves. The stems of water horsetails are entirely hollow, and smoother than those of marsh horsetails. The stems pull apart easily at the joints.
See Equisetum for a comparison chart.
Leaves: Each stem node is wrapped with tiny, black, sharp-tipped scale leaves. Branch nodes also have miniscule leaves that appear as black dots. The leaves do not perform photosynthesis; this is done by the stem and branches.
Fruits: The spore-bearing, conelike strobili are yellow-green, ⅜-¾" (1-2 cm) long.
Cobb, Boughton, Farnsworth, Elizabeth & Lowe, Cheryl, Peterson Field Guides: A Field Guide to Ferns and Their Related Families of Northwestern and Central North America, Houghton Mifflin Company, 2005, p. 342
Equisetum fluviatile at the Lady Bird Johnson Wildflower Center
Equisetum fluviatile on Wikipedia
Equisetum fluviatile on Plants for a Future, a resource and information centre for edible and otherwise useful plants
Equisetum fluviatile on eFloras
Equisetum fluviatile description by Thomas H. Kent, last updated 1 Dec 2020.