Equisetum telmateia (great horsetail or northern giant horsetail) is a species of Equisetum (horsetail) with an unusual distribution, with one subspecies native to Europe, western Asia and northwest Africa, and a second subspecies native to western North America. The North American subspecies is often simply but ambiguously called "giant horsetail", but that name may just as well refer to the Latin American Equisetum giganteum and Equisetum myriochaetum. It is a herbaceous perennial plant, with separate green photosynthetic sterile stems, and pale yellowish non-photosynthetic spore-bearing fertile stems. The sterile stems, produced in late spring and dying down in late autumn, are 30-150 centimeter (rarely to 240 centimeter) tall (the tallest species of horsetail outside of tropical regions) and 1 centimeter diameter, heavily branched, with whorls of 14-40 branches, these up to 20 centimeter long, 1-2 millimeter diameter and unbranched, emerging from the axils of a ring of leafs. The fertile stems are produced in early spring before the sterile shoots, growing to 15-45 centimeter tall with an apical spore-bearing strobilus 4-10 centimeter long and 1-2 centimeter broad, and no side branches; the spores disperse in mid spring, with the fertile stems dying immediately after spore release. Occasional plants produce stems that are both fertile and photosynthetic.