Hortus Botanicus Leiden, Netherlands

Common name: Reuzenschaafstro, Giant scouring rush

Family: Equisetaceae (Horsetail family)

Distribution: North America

Hardiness: Zone 05

Life form: Fern

Comments: Horsetails belong to a very ancient group of ferns, and are the only remaining genus of a much larger group that knew its greatest diversity and distribution during the Devonian and Carboniferous, more than 300 million years ago. The group then also contained huge trees, such as the giant Calamites fossil. Horsetails are spore plants with whorled branches, often with a hollow stem such as this huge scouring rush. The giant scouring rush has unbranched stems with scaly leaves fused into a sheath. The spores are produced in terminal strobili, and are dispersed by the wind. Because of the fast-growing creeping rhizomes, the Hortus grown its horsetails in containers. In the Netherlands eight species of horsetails occur in the wild. The giant scouring rush originates in North America and was formerly called Equisetum hyemale var. robustum.