Horsetail is an ancient plant dating back to approximately 350 million years ago. Due to its unique expression, common names also include scouring rush, bottle brush, and shavegrass. Equisetum arvense is considered a nutritious herb and is usually decocted as horsetail tea and infused into herbal vinegars and tonics. Horsetail has a recorded history going back to the Devonian period. The plant at that time was as tall as a modern palm tree. Horsetail, not to be confused with cat-tail, is possibly the most abundant source of silica in the plant kingdom, so much in fact that the herb can be used for polishing metal. It got the name "scouring rush" from this very application. It has had other uses during the ages including as an ingredient in shampoos, skincare products, and in dietary supplements. Horsetail belongs to the Equisetaceae plant family.