About Equisetum giganteum L.
Equisetum giganteum L. is one of the largest known horsetail species. It typically grows 2–5 metres (6.6–16.4 ft) tall, and is only exceeded in height by the closely related Equisetum myriochaetum. E. myriochaetum can grow up to 8 metres (26 ft) tall when it relies on surrounding plants for support. One form or variety of Equisetum giganteum has been recorded reaching 11 m (36 ft) in height in Venezuela, and 12 m (39 ft) in height in the Pantanal region of Brazil. This species has the stoutest stems of any horsetail. Stems are normally 1–2 cm in diameter, and can reach up to 3.5 cm in diameter in some populations. The stems produce numerous whorls of very slender branches, with as many as 56 scale-like leaves per whorl, though it remains unclear whether all of these leaves would produce branches. These branches do not branch further, and some terminate in spore cones. Unlike many other horsetail species, Equisetum giganteum does not produce two separate types of stems: photosynthetic sterile stems and non-photosynthetic spore-bearing stems. Populations of this plant from northern Chile with very stout stems up to 3.5 cm in diameter have sometimes been classified as the separate species Equisetum xylochaetum, but this separation is not widely accepted by botanists.
