A Herb of Saturn, Ancient and Enduring

Culpeper placed horsetail under Saturn, the planet of age, endurance and the mineral earth, a fitting ruler for a stiff, silica-laden plant of immense antiquity. In folk correspondence horsetail carries meanings of endurance, ancient wisdom and the strength that comes of great age, read from its living-fossil lineage and its abrasive, rock-like toughness. Its practical scouring use and its role as one of the oldest surviving plant forms on earth give it a quiet symbolism of persistence, a green thing that has outlasted whole worlds of vanished forests and still stiffens itself with the stone of the ground it grows in.

A plain agricultural caution belongs with the plant despite its name: horsetail contains an enzyme, thiaminase, that destroys thiamine, so that hay heavily contaminated with the plant can cause a genuine, documented vitamin deficiency and neurological illness in horses and other grazing livestock if eaten over time in quantity, an irony given the plant's common name and its old reputation as a herb of strength and endurance. In small amounts and mixed pasture the risk is low, and the danger is a matter of veterinary record rather than any claim about the plant's use in human herbal tradition, where dried horsetail is still sold today as a source of dietary silica.