Common Horsetail, Field Horsetail: Equisetum arvense (Synonyms: Equisetum arvense var. alpestre, Equisetum arvense var. boreale, Equisetum arvense var. campestre, Equisetum arvense var. riparium, Equisetum calderi) -
Ferriss' Scouring Rush: Equisetum x ferrissii (Synonym: Equisetum hyemale var. elatum) -
River Horsetail, Swamp Horsetail, Water Horsetail: Equisetum fluviatile (Synonyms: Equisetum fluviatile var. limosum, Equisetum limosum) -
Common Scouring-rush, Common Scouring-rush, Scouring-rush Horsetail, Dutch Rush, Prairie Scouring-rush: Equisetum hyemale var. affine (Synonyms: Synonyms: Equisetum affine, Equisetum hyemale ssp. affine, Equisetum hyemale var. californicum, Equisetum hyemale var. pseudohyemale, Equisetum hyemale var. robustum, Equisetum praealtum, Equisetum robustum, Hippochaete hyemalis, Hippochaete hemalis ssp. affinis) -
Smooth Horsetail, Smooth Scouring-rush: Equisetum laevigatum (Synonyms: Equisetum funstonii, Equisetum kansanum, Equisetum laevigatum ssp. funstonii, Hippochaete laevigata) -
Marsh Horsetail: Equisetum palustre (Synonyms: Equisetum palustre var. americanum, Equisetum palustre var. simplicissimum) -
Giant Horsetail, Great Horsetail: Equisetum telmateia ssp. braunii (Synonyms: Equisetum braunii, Equisetum maximum, Equisetum telmateia ssp. braunii) -