Equisetales

The Equisetales are an order of primitive, spore-bearing vascular plants, with most members now extinct. The sole living genus is Equisetum, commonly known as horsetails or scouring rushes. These plants are characterized by jointed stems and whorled leaves and branches.1

The extinct members of this group, which date back to the Devonian Period, included herbaceous plants, shrubs, and even trees up to 30 meters tall, such as Calamites. The modern horsetails are much smaller and are found worldwide, typically in damp environments, though some have adapted to drier conditions. While the extinct giant horsetails contributed to coal beds, living species have limited economic importance, though some are used for their abrasive, silica-rich cell walls. The family Equisetaceae contains the single living genus Equisetum.12