Original: They are perennial plants, either herbaceous and dying back in winter as most temperate species, or evergreen as most tropical species and the temperate species Rough Horsetail (E. hyemale), Branched Horsetail (E. ramosissimum), Dwarf Horsetail (E. scirpoides) and Variegated Horsetail (E. variegatum).
Simplified: They are perennial plants, either herbaceous, they back in winter (most temperate species) or they are evergreen (some tropical species, and the temperate species Equisetum hyemale, E. scirpoides, E. variegatum and E. ramosissimum).