Horsetail

Horsetail, genus Equisetum, is a group of primitive, vascular plants in the family Equisetaceae. It is considered a living fossil, with a fossil record dating back to the late Paleozoic era. Today, horsetails are distributed worldwide in temperate and some subtropical regions.

Horsetail plants are perennial and primarily grow as two types of shoots: sterile, green, photosynthetic shoots and fertile shoots that bear a cone-like strobilus at the tip. The stems are hollow, jointed, and ribbed, and leaves are reduced to small scales that form a sheath around each node. The plant reproduces by spores rather than seeds, and rhizomes spread underground to help form clonal stands.

In reproduction, the sporophyte produces sporangia on the strobili, releasing spores that grow into free-living gametophytes. Fertilization requires standing water, and after fertilization, a new sporophyte develops from the resulting zygote. The life cycle is a classic example of alternation of generations, with the diploid sporophyte predominating.

Horsetails typically inhabit moist environments such as streamsides, wetlands, damp meadows, and disturbed or nutrient-rich soils. They are often found in temperate regions and can become weedy in lawns or agricultural margins. The plants are notable for their high silica content, which historically made them useful as an abrasive for polishing and cleaning.

Caution is advised with some traditional uses, and horsetails are not generally used for culinary purposes. Species vary in habitat preference and growth form, with several common species including field horsetail and scouring rush.