horsetails

Horsetails, or Equisetum, are a small group of ancient vascular plants and the only living genus in the family Equisetaceae, order Equisetales. They have a fossil record that extends back to the Devonian period and once included many more forms. Today horsetails are found worldwide, most commonly in damp, nutrient-rich soils in temperate and subtropical regions.

Description: Horsetails are perennial, herbaceous plants with hollow, jointed stems that rise from rhizomes. The stems are ribbed and rough with abundant silica; leaves are reduced to small scales, and at each node a whorl of green, photosynthetic branches forms a brushlike crown. Sterile shoots are usually green; fertile shoots carry a terminal strobilus bearing sporangia.

Life cycle: Horsetails reproduce by spores rather than seeds. Spores are produced in cone-like strobili on fertile shoots. The spores germinate into a free-living, photosynthetic gametophyte that generates both eggs and sperm. The resulting sporophyte is the dominant phase and the familiar plant appears as described above.

Habitat and ecology: They commonly grow on damp or periodically flooded soils, riverbanks, wetlands, and disturbed sites. Some species are pioneers in harsh environments; others tolerate shade or drought. They are slow-growing and can be indicators of moist soils; their silica-rich stems resist rapid decomposition, contributing to their persistence in some habitats.

Uses and significance: The silica-rich stems have been used as abrasive scrubbing tools and for polishing. Horsetails are sometimes grown as ornamental plants or studied for ecological and paleobotanical significance.