Modern Equisetum is much smaller than their extinct ancestors. Today Equisetum is only genus in Equisetaceae . It could possibly be the oldest living genera of vascular plants in the world today since the oldest fossil found dates back to the Devonian Era. During this time it is possible that both the herbaceous and the arborescent co existed for some time together. Currently it is a cosmopolitan plant dispersed world wide except for Australia and New Zealand.
Most concentration is in Northern Hemisphere with a few in the tropics and Southern Hemisphere.
There are small species in Arctic and Alpine regions with one species in the Arctic Circle. Equisetum is found mostly in wet lands all though some are adapted to mesophytic conditions. Equisetum is considered a noxious weed especially by cattle and horse men since a few species are toxic to live stock. Found one reference of a species used in Costa Rica which is used medicinally as treatment of kidney trouble in humans. Equisetum contains a considerable amount of silica which lent to use as an abrasive, important in polishing and scouring, hence the common name scouring rush.