Equisetum fluviatile L.
Family: Equisetaceae
pipes, river horsetail, water horsetail
Equisetum fluviatile image
Christopher Noll  
Etymology: Equisetum: Latin for "horsetail" from equus, "horse," and seta, "bristle"
Plants: erect, perennial, to 40" tall, semi-aquatic, emergent aquatic, stem is 80\% hollow; stems hollow, stiff, with vertical ridges, contain much silica, jointed at nodes,; from rhizomes
Leaves: 15-20 pointed, dark brown-black, toothed membrane circling each node
Habitat: moist; marshes, shallows, water less than 40" deep