Tansy (Tanacetum vulgare) is a tall, aromatic daisy-family herb crowned in late summer with flat clusters of gold, button-like flowerheads and cloaked in fern-cut, glossy leaves that smell sharply of camphor, rosemary and bitter herbs. Once a fixture of the medieval and early-modern kitchen — pounded into "tansies," the green, faintly bitter baked puddings and cakes eaten at Easter, and steeped into cordials and bitter ales — it has all but vanished from cooking today, its warning-strong flavour and toxic thujone content having pushed it firmly out of the modern larder.