No relation to : Tansy-Leaved Phacelia (Phacelia tanacetifolia) [a flower belonging to a differing family].
In addition there does exist a
Rayed Tansy (Tanacetum macrophyllum) which has slightly larger yellow flowers with rays (7-13mm across) and of similar height (1.2m) but which is much less common occurring mainly in northern England and Scotland.
A much commoner flower belonging to the same genus (Tanacetum) is Feverfew (Tanacetum parthenium) but that is much shorter at only 70cm high and has much larger flowers (15-23mm across) which have white rayed florets with yellow disc-florets in the centre, the leaves are also very different. This too, like Tansy, is strongly aromatic.
Uniquely identifiable characteristics
Used to be called: Chrysanthemum Vulgare.
Tansy spreads by underground stolons.
The leaves are bitter and spicy and once used to make Tansy (a custard pudding), but it may be poisonous if taken internally. Indeed, both
Ragwort and Tansy contain Pyrrolizidine Alkaloids which are moderately poisonous. Ingesting excess Tansy can cause permanent liver damage, digestive disturbances, lack of coordination, weakness, staggering, and death. Cattle are only vulnerable when Tansy is present as an unwanted inclusion within the hay or when wilted, for otherwise they don't usually touch it. The toxins within are not destroyed on storage or drying. It can contaminate milk and honey. Gloves should be worn if up-rooting Tansy by hand, for the alkaloids present, including Tanacetin, are readily absorbed through the skin.
Tansy is a member of the Daisy & Dandelion family, but un-like most members, possesses no ray florets, only central disc florets. In America it spreads readily and is a controlled weed.
The stem leaves are very similar to those of Leptinella (Cotula squalida) but the flowers of Leptinella are in singles atop a stalk which is very much shorter than that of Tansy. Also, the flowers, although both are yellow and both are lacking ray-florets, are very much less compacted than those of Tansy.
Traditionally, Tansy was used for treating tapeworm, roundworm and threadworm and as a stimulant for migraine, loss of appetite and liver problems. Sprigs of Tansy were placed in the house to keep flies at bay. The flower heads yield commercial insecticides, (Pyrethrin I and Pyrethrin II) and were once used to treat lice.
Large consumption of Tansy can be fatal, due mainly to Thujone in the essential oil. Symptoms of poisoning include abdominal pains, serious gastroenteritis, convulsions, tachycardia, arrhythmia, liver and kidney damage, loss of consciousness and finally death.
Possessing natural insecticidal properties Tansy was sometimes planted (or allowed to grow) near or within crop plants on farmland in order to keep pests at bay without recourse to modern insecticides (which may not have been as effective in past times).
A yellow dye can be extracted from the flowers.
Tansy contains the allergenic Sesquiterpene Lactone, Arbusculin A, which may be an effective treatment for Lymphoid Leukaemia. Because of this toxic substance, Tansy can induce contact hypersensitivity as can other similar sesquiterpene lactones found in many other flower genera.
Senecionine is also present.
Tansy also contains other sesquiterpene lactones such as
Thujone is another constituent of Tansy. Note the strained three-membered carbon ring of cyclopropane, the instability of which (cleavage of the ring) probably significantly contributes to the toxicity of Thujone. It has the odour of a similar but not identical compound called Menthol, which is responsible for the aroma and taste of some Mints.
Junipers, Mugwort, Wormwood (from which the alcoholic beverage absinthe is made) and common sage also contain some thujone. Thujone has only a minute presence in the absinthe. It is moderately toxic and acts on some neurotransmitter receptors within the brain and is thus a neurotoxin too. The toxicity of Tansy is mainly due to the presence of β-Thujone in the essential oil, amongst Camphor and other
Senecionine (aka Aureine and Squalidine) is a |
pyrrolizidine alkaloid which is hepatotoxic, damaging the liver on ingestion, and found in Tansy and also in species of Senecio [in the Daisy Family] (which includes
Ragworts such as Oxford Ragwort, Groundsels) and species of Crotalaria (a member of the Pea Family) which grows in the tropics. Senecionine has uses in the biological laboratory.
Tansy also contains |
camphene and Myrtenol, or oil of myrtle, a constituent of Bog Myrtle. These substances contribute to Tansy being an effective insect repellent and insecticide.
Camphene is an aromatic hydrocarbon and bicyclic monoterpene which has a faint smell reminiscent of Camphor. Virtually insoluble in water it is present in
turpentine oil, nutmeg, lemon,
juniper berries, bergamot oil, cinnamon oil, camphor oil,
citronella oil, ginger oil, neroli, cypress oil and Valerian. It is used in fragrances and somewhat strangely as a food additive for flavouring. Like camphor, it tends to sublime (slowly evaporates without melting).
Some books confuse |
Tanacetol with Thujone (shown above), equating the two, but as can be seen here, they are quite different. The active moieties in Tanacetol A are on the oxygen atoms, of which there are four.
Germacrene D is one of the essential oils that are typically accompanied by
Cadinane and Muurolene sesquiterpenoids, which are similar in chemical structure to Germacrene but with variations; a consistent variation being the bond joining the two rings. Germacrenes are typically produced in a number of plant species specifically for their insecticidal and anti-microbial properties, which the plant uses in defence. Therefore it is somewhat counter-intuitive that they are also extant in playing a role as insect pheromones, attracting the very insects they are trying to poison; perhaps in an effort to kill as many as possible(?). But perhaps it instead repels unwanted species of insects whilst attracting others for pollination duties which the insects unknowingly perform as they suck up any nectar from the flowers?
Tansy also produces
terpenoids (α-Amyrin and β-Amyrin).