The young plants are eaten cooked or raw, but considerable care must be taken. If eaten over a long enough period of time, some species of horsetail can be poisonous to grazing animals, including horses. The toxicity appears to be due to thiaminase, which can cause thiamin (vitamin B1) deficiency.
Dwarf scouring rush, also called dwarf horsetail, is a hardy grass plant distantly related to ferns. This evergreen rush has a 2.5-20cm (1 to 8 in) tall stem that twists and bends into gnarly patches.