Tansy
Tanacetum vulgare
They rubbed it on the dead to keep the flies away. Then they rubbed it on themselves.
Overview
Tansy is a bitter, aromatic, gold-buttoned herb of roadsides and riverbanks, with a smell so strong and so particular — sharp, medicinal, faintly like camphor and something older — that it is either bracing or repellent depending entirely on who is doing the smelling. It was rubbed into meat to preserve it. It was strewn on floors and packed into coffin shrouds as an insect repellent. It was eaten at Easter in tansy cakes and puddings, a tradition tied to Lenten fasting that ended with a dish bitter enough to recall the bitter herbs of Passover and, practically, to expel the intestinal worms that a winter of poor diet had encouraged. All of these uses involve the same compounds — thujone and camphor — in different quantities and with different intentions. The line between tonic and poison ran, as it often does, through the dose.
Botanical Notes
A robust, spreading perennial reaching 60–120cm with pinnately divided, dark green, fernlike leaves that are strongly and persistently aromatic when crushed. Flat-topped clusters of small, bright yellow, button-like flower heads — ray florets absent — from July to October. Spreads vigorously by rhizome and self-seeding; can become dominant in disturbed ground. Found on roadsides, riverbanks, field margins, and waste ground throughout Europe and Asia, naturalised throughout North America. The essential oil contains up to 70% thujone in some chemotypes — the compound responsible for both its insecticidal and its toxic properties.
Lore & History
Tansy cakes were an Easter tradition recorded from the twelfth century onward — bitter pancakes or puddings eaten on Easter Sunday and the days following, understood as both a digestive purge after Lent and a ritual echo of the bitter herbs of the Passover Seder. The tradition persisted in England into the nineteenth century before fading, the bitterness of the herb apparently becoming less appealing as diets improved. Medieval embalmers used tansy with other aromatic herbs — along with wormwood and rue — to slow decomposition and deter insects. In folk magic, tansy was planted near doorways and worn on the body as protection, and it was used in flying ointments for the same reason wormwood and mugwort were: its volatile compounds, absorbed through skin, have genuine neurological effects.
Warnings
Thujone content varies dramatically between plants but can be high enough to cause serious toxicity at culinary doses, particularly in the root oil. Internal use of tansy preparations is not recommended — the historic Easter tansy cakes caused documented poisoning when made with too much plant material. The fresh plant is more toxic than dried. Avoid entirely during pregnancy — strongly emmenagogic and abortifacient. Contact with fresh plant may cause dermatitis in sensitive individuals. Historically used as an abortifacient at dangerous doses; do not attempt to use it for this purpose.