This section is from the book "British Wild Flowers - In Their Natural Haunts Vol2-4", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
Usually associated with cultivation or gardens, this plant has been met with in Early Glacial beds at Beeston, Norfolk, at the base of the Arctic freshwater bed. It is found in the North Temperate and Arctic Zones in Arctic Europe, Siberia, N.W. America, and has been introduced into the United States. It is general in Great Britain, but is not found in Cardigan, Flint, Mid Lancs, Linlithgow, Main Argyle, Dumbarton, and is often naturalized. In Scotland it is doubtfully wild, and certainly not so in Ireland.
Tansy is one of the plants whose status is very doubtful. It may be found by the side of a stream in an apparently native station, or by the roadside at a distance from a house, or along the hedgerows, in fields of corn, where it has been said to be a pest, difficult to eradicate. At other times it turns up on waste ground, and is then undoubtedly a straggler from elsewhere. It is often to be seen growing in cottage gardens.
The robust, upright, usually simple, smooth stem of the Tansy, with its leaflets divided almost to the base with finely toothed segments, is very characteristic in its habit. It grows in bushy clumps, excluding all other tender vegetation.
The small yellowish flowerheads are arranged in a terminal corymb, the florets are all tubular, or if ligulate longer than the others, and are flat or slightly convex, like buttons. There are no bracts upon the flower-stalks. The inner bracts of the involucre are blunt, the outer not so long, tough, with a mem-branous margin, scarious. The fruit is inversely egg-shaped and 5-ribbed.
The stems are usually 2 ft. high. Flowers may be sought in July and August. It is a herbaceous perennial, increased by division of roots, and often cultivated.
There are several hundred florets which form a flat disk, with no ray florets. It is thus, in spite of the absence of the latter, rendered conspicuous and accessible to insects, which can pass over the whole surface and cross-pollinate many florets together, which pollen-seekers find an advantage, and this causes the flower in turn to be much sought after. The honey is easily got at, because the tube is only 1 mm. deep. The style aids the simultaneous cross-pollination by insect visitors. It has a capitate tuft of spreading hairs, and in the first stage presses the pollen out of the cylinder, raising it so that it is swept off by insects, and in the second stage the two lobes spread out with papillae on the inner side. Tansy is visited by the Hymenoptera, Apis, Colletes, Halictus, Andrena, Sphecodes, Dinetus, Mellinus, Crabro, Odynerus; Diptera, Odontomyia, Eristalis, Syrphus, Syritta, Melithreptes, Sarco-phaga; Lepidoptera, Polyommatus, Vanessa, Hadena, Botys; Coleo ptera, Coccinella; Hemiptera, several species of Thrips; Neuroptera, Panorpa.
Photo. B. Hanley - Tansy (Tanacetum Vulgare, L.)
Though there is no pappus the achenes have a membrane, and are aided by this means by the wind in their dispersal. This plant grows on sand soil, being a sand-loving plant, or on alluvium on sandy loam.
A fungus, Puccinia tanaceti, the sun-flower rust, may be found on the leaves.
Three beetles, Chrysomela graminis, C. menthastri, Adimonia tanaceti; a Hymenopterous insect, Colletes fodiens; several Lepidop-tera, Ringed Carpet (Boarmia cinctaria), Essex Emerald (Geometra smaragdaria), Cleodora striatel/a, Pterophorus dichrodactylus, Dicro-rampha alpinana, D. tanaceti; a Homopterous insect, Phytocoris ulmi; and 4 Heteroptera, Camptobrochis tubescens, Orthocephalus mutabi/is, Macrocoleus molliculus, and M. tanaceti, are found on it.
Tanacetum, Pliny, originally Athanasia, or immortality, of which it is a corruption, is from the Greek, thanatos, death; and the second Latin name emphasizes its universal character.
Tansy is also called Bachelor's Buttons, Buttons, Bitter Buttons, English Cost, Fern (Parsley, Scented), Ginger, Ginger-plant, Joynson's Remedy Cheese, Tansy. It is called Scented Fern from its fern-like leaves and scented smell, and Bitter Buttons from the shape of the flowerheads and bitter taste of the whole plant.
The smell is strong and aromatic. The plant is very bitter, and is regarded as a stimulant and carminative. The seeds were supposed to be sudorific. It is said to drive away bugs. A distilled water and bitter for stomach complaints are made from it. The young leaves are shredded, and used to give colour and flavour to puddings, omelets, and cakes. The curled variety is used for garnishing. It is frequently grown in the garden.
Essential Specific Characters:161. Tanacetum vulgare, L. - Stem erect, rigid, leafy, dark-green, leaves bipinnatifid, leaflets serrate, flowerheads numerous, yellow, corymbose, terminal, outer florets longer than phyllaries.