This is the largest Equisetum sp. (Horsetail) in Illinois; it is somewhat unusual in having evergreen stems. I am always impressed by the large dense colonies that are often formed by the stems of this plant. These tough stems were used to scour pots, pans, and floors during pioneer days, hence the common name. However, the Scouring Rush is not a rush, but a horsetail. The horsetails are closely related to ferns and both were common during the Carboniferous period (280-345 million years ago), when tree-sized horsetails and ferns occurred. The coal deposits of Illinois were formed in large part from the ancestral plants of today's horsetails and ferns. Scouring Rush can be distinguished from other horsetails in the state by its large size, rough unbranched stems, and pointed cones. While there is some variability across local populations, this species is usually easy to identify. However, sometimes it forms sterile hybrids with other horsetails. When this occurs, it is possible to confuse the hybrid with one of the parent species.