Equisetum palustre

Equisetum palustre, the marsh horsetail, is a perennial herbaceous pteridophyte in the family Equisetaceae, part of the horsetail subclass Equisetidae. It has scarcely branched stems 10 to 60 centimeters tall, roughly 1 to 3 millimeters across with 8 to 10 ribs, and loose green leaf sheaths bearing 5 to 10 narrow, dark toothed lobes with lighter edges. It is widespread across cooler regions of Eurasia and North America, growing in nutrient rich wet meadows as well as ditches, roadsides and peat-based ground such as that found in Finland. The plant is poisonous to mammals, most often reported as potentially fatal to horses, since it contains alkaloids that destroy vitamin B1, though some sources describe it as safe to eat in moderation when properly cooked because heat breaks down the thiaminase enzymes responsible.