There is only one genus of horsetails (Equisetum) with about fifteen to twenty species alive in the world today. Horsetails are primitive plants whose tree-like ancestors were the dominant plants during the Carboniferous Age about 230 million years ago. Today they can be found throughout the world except Antarctica. Along with club mosses and ferns, horsetails are the only vascualr plants in the world today that reproduce by spores.
Common horsetail (Equisetum arvense) is a perennial native to North America. Also called field horsetail or jointgrass, common horsetail is dimorphic, that is, it has two forms, sterile and fertile. The fertile stem appears in the early spring and is non-photosynthetic. After releasing its spores, the fertile stem withers and the sterile green stems appear.
These pictures, taken at the Baker Day Use Area along the North Umpqua River (Oregon) are of sterile stems. These sterile, hollow, aerial stems arise from a tuber-bearing underground rhizomous system and are composed of jointed segments. Whorls of side branches are borne at the conspicuous nodes. The stem and branches are green and photosynthesize. The non-photosynthetic leaves of common horsetail are small, scale-like and fused at the base to form a sheath around the jointed stem.
Often found in moist soils, common horsetail can also thrive in dry soils once established. It can often become weedy and invade fields, roadsides and waste areas.
Since Greek and Roman times Equisetum species have been used as an herbal remedy and eaten. The young shoots, both fertile and sterile, are edible when peeled and cooked. Traditionally horsetail is used to heal ulcers and wounds, treat tuberculosis and kidney problems and as a diuretic. I personally would not ingest horsetail. Horsetails absorb heavy metals and chemicals from the soil which is enough to dull my appetite. The high silica content in horsetails may irritate the urinary tract and kidneys. Horsetails also contain thiaminase, and enzyme that destroys Vitamin B-1 stored in the body. Although thiaminase is rendered harmless by thorough cooking, I am never hungry enough to chance eating horsetails.
My next post will show the fertile stem.