Mugwort: the St John’s herb, thujone, allergies and safe use
Common mugwort (Artemisia vulgaris) is a wild European plant linked to St John’s Day. Its history, folklore, thujone, allergies and precautions before you burn it.
Key points
| Botanical name | Artemisia vulgaris |
|---|---|
| Family | Asteraceae (the daisy family) |
| Origin | Europe, Asia, North Africa; naturalised in North America |
| Height | Up to 1.5 m, green leaves on top, silvery underneath |
| Compound to watch | Thujone, present in the plant |
| Tradition | St John’s herb, belts and wreaths, flavouring of old beers |
| Main precaution | Not advised during pregnancy; allergenic pollen; not to be confused with wormwood |
What is mugwort?
Common mugwort (Artemisia vulgaris) is a perennial in the Asteraceae family, like the daisy and the artichoke. It grows on waste ground, along paths and on riverbanks, in soils poor in nitrogen. Its often reddish stems bear deeply cut leaves, green on top and silvery and woolly underneath; small, inconspicuous flowers appear at the end of summer. Crushing a leaf releases a herbaceous, bitter and slightly camphor-like smell.
The genus Artemisia includes many species, among them wormwood (A. absinthium), annual mugwort (A. annua) and Chinese mugwort (A. argyi). They are not interchangeable: each has its own compounds and its own precautions.
Origin of the name and the St John’s plant
Ancient tradition links its name to Artemis, the Greek goddess of hunting and nature; the etymology is old but debated. In the Middle Ages, the plant was called “St John’s girdle” (cingulum Sancti Johannis): it was said that John the Baptist had worn one. On St John’s Eve, 23 June, belts, wreaths or bunches of mugwort were worn, hung on doors or thrown into bonfires, depending on the region and the folklorists consulted. These gestures belonged to the summer solstice festival and to a symbolic protection of the home. Echoes of them survive in Germany and the Netherlands, where mugwort is sometimes called the “St John’s plant.”
Mugwort also flavoured drinks: in early England, its flowers scented beer before hops arrived, and it was part of the herb blends used in “gruit ales.”
What tradition says, what science says
In popular traditions, many roles are attributed to mugwort: protection of travellers, more vivid dreams, divination. These are beliefs, which we report as they are. The only scientifically established point is that the plant contains thujone, a molecule that, at high doses, acts on the nervous system. Some authors see in thujone the explanation for the more intense dreams attributed to mugwort smoke or infusion; no solid study demonstrates this for smoke.
Traditional Chinese medicine, for its part, burns cones or sticks of leaves from a related species for moxibustion. This is a distinct practice, applied by practitioners close to the skin; do not imitate it at home without training.
Precautions
- Pregnancy and breastfeeding: mugwort is traditionally described as stimulating to the uterus. Avoid any concentrated exposure (infusion, oil, prolonged smoke) and ask your doctor for advice.
- Allergy: mugwort pollen is one of those that cause hay fever in late summer. People already allergic to Asteraceae (ragweed, daisy, sunflower) are more likely than others to react, and the dried plant can also irritate the skin.
- Thujone: no mugwort essential oil for personal use (see Essential oils: caution).
- Smoke: as with any burned plant, use occasionally, in a ventilated room, with no vulnerable person present.
See also common sage, another thujone-containing plant.
Harvesting mugwort
Mugwort is very widespread, but do not pick it just anywhere: along roads, treated fields and dumps, the plant concentrates pollutants. Avoid protected areas. Cut flowering stems mid-season, in dry weather, and leave the plant to regrow. Dry them upside down, in a dark, airy place (see Drying and storing your herbs). A wild plant identified with certainty is better than a purchase of unknown origin, but if you are in doubt about the species, do not burn it. It can resemble toxic plants, such as ragweed (allergenic) or certain members of the carrot family (Apiaceae).
In a region where it invades habitats (as in North America), harvesting it can even help to contain it.
St John’s Eve rituals, the safe version
If you wish to mark the summer solstice, a wreath or bunch of dried mugwort hung on a door is a harmless symbolic gesture. Avoid smouldering the plant for long in a closed room. If you light an outdoor fire, follow local fire-prevention rules and keep water close at hand. For the summer solstice, see our page on Litha.
Frequently asked questions
Is mugwort the same plant as wormwood?
No, but they are cousins. Wormwood is Artemisia absinthium; common mugwort is Artemisia vulgaris. Their uses and precautions differ.
Can you burn mugwort?
You can burn small quantities of dried mugwort from time to time, in a ventilated room. Avoid it if you are pregnant, allergic to Asteraceae, asthmatic, or if young children are present.
Is mugwort dangerous?
In a small decorative amount, it is not very dangerous. It is swallowing concentrated products (oil, extracts) that exposes you to thujone. Ask a health professional for advice before any internal use.
Why is it called St John’s herb?
Because, according to folklore, it was gathered and carried on St John’s Day, at the summer solstice. The exact origin of the custom is still debated.
Does mugwort give strange dreams?
Tradition says so, but nothing has established it for smoke. Treat it as a folk tale, not as a safe effect.
Also read
The meanings mentioned belong to tradition and symbolism. They are neither promises of results nor medical advice. Back to Herbs, waxes and accessories.