Horsetail (Equisetum hyemale), also called rough horsetail or scouring rush, is a non-flowering evergreen perennial. It has vertical green stems with horizontal bands, similar to bamboo, but the stems are skinny, like tall grass, and it reproduces through spores (not seed), like ferns. However, horsetail is not related to bamboo or grass or ferns. Its species dates back to Paleozoic times, some 350 million years ago. Horsetail grows in wet conditions and can even grow in standing water. For this reason, it is commonly used to decorate water gardens or swampy areas where few other plants can survive. Horsetail spreads via rhizomes and is such an aggressive spreader.