Christian Ziegler / Horsetail (Equisetum sp) stand in a swamp, Jasmund National Park, Ruegen, Germany

Christian Ziegler / Horsetail (Equisetum sp) close-up detail, Jasmund National Park, Ruegen, Germany

Christian Ziegler / Horsetail (Equisetum sp) stand in a swamp, Jasmund National Park, Ruegen, Germany

Philippe Clement / Close up of stem of Common scouring rush {Equisetum hyemale} Luxembourg

Jason Smalley / Horsetail {Equisetum} growing round Silver Birch {Betula verrucosa} UK.

Juan Manuel Borrero / Horsetail {Equisetum telmateia} Spain

Juan Manuel Borrero / Horsetail {Equisetum telmateia} Spain

Michio Hoshino / Bearberry (Arctostaphylos uva ursi), Blueberry (Vaccinium sp), and Horsetail (Equisetum sp) in trundra, Alaska

Gerry Ellis / Field Horsetail (Equisetum arvense), Pacific coast, North America

Gerry Ellis / Field Horsetail (Equisetum arvense) among other various vegetation, Pacific coast, North America

Piotr Naskrecki / Field Horsetail (Equisetum arvense) stems topped with spore-producing strobilus, Estabrook Woods, Massachusetts