Field horsetail and related species, Equisetaceae

Abstract

The Horsetail (Equisetaceae) family comprises 30 species, all in the ancient genus Equisetum. During the Carboniferous age (more than 230 million years ago), the Horsetail family was the dominant plant group in the world, with plants reaching gigantic size. Two basic forms of horsetails survive today. One is the hollow, jointed, and leafless scouring rush. The other is the horsetail with whorls of slender, green, jointed branches around hollow, jointed stems, often occurring in great numbers, giving the appearance of a horse’s tail.