Species:
     Equisetum arvense   (common or field horsetail)  (5 images)
     Equisetum ferrissii   (intermediate scouring-rush, Ferriss's horsetail)
     Equisetum hyemale ssp. affine   (common scouring-rush)  (6 images)
     Equisetum laevigatum   (smooth scouring-rush)  (8 images)