This section is from the book "Wayside And Woodland Blossoms", by Edward Step. Also available from Amazon: Wayside And Woodland Blossoms: A Guide To British Wild-Flowers.
Time was when every cottage garden and every kitchen garden had its clump of Tansy, for it was a valued item in the housewife's pharmacopoeia, and was all but invaluable in cookery. A belief is entertained by some botanists that the Tansy-plants growing wild in waste places by field and roadside throughout the country are garden escapes, or their descendants, that have become naturalized.
The Tansy is a perennial, with creeping rootstock, from which arise beautiful broad feathery radical leaves and flowering stems. The leaves are very deeply divided in a pinnate or bi-pinnate manner, the segments toothed. The angled stem reaches a height of about two feet, and then branches off into a corymb of flower-heads. Each flower-head is enclosed in a half-rounded involucre of leathery bracts. There is an outer row of ray-florets, but they are very short, and of the same dull yellow colour as the disk-florets; they are pistillate only, whilst the disk-florets are all staminate. Flowers during August and September.
All parts of the plant give off a strong aromatic scent when touched or handled, and the taste is exceedingly bitter, a quality which caused it to be used as a stomachic tonic and a vermifuge.
This is the only British species of the genus, whose name is said to be a corruption of Athanasia deathless; but probably it is not so derived.