Common Name: Qing Hao

General Information

Artemisia annua is a sweetly aromatic, much-branched, annual plant with a taproot; it can grow 70 - 200cm tall, exceptionally to 300cm[, , ].
The plant has a long history of medicinal use, especially in China. It has recently been shown to be a very effective antimalarial and it is now widely cultivated for its medicinal aromatic oils[],
Artemisia annua often persists in gardens, becoming naturalized in moist-temperate areas (especially in eastern United States)[]. It has become a weed of waste places in many areas of the world[]. Reports of naturalization in N. America may be exaggerated[].

Known Hazards

The plant contains potentially allergenic sesquiterpene lactones. Skin contact with the plant can cause dermatitis or other allergic reactions in some people[].
The pollen is extremely allergenic[].

Botanical References

, ,

Range

Originally native to southeast Europe and western Asia, but widely naturalized through Europe, Asia, N. America and N. Africa.

Habitat

Hills, waysides, wastelands, outer forest margins, steppes, forest steppes, dry floodlands, terraces, semidesert steppes, rocky slopes, roadsides, saline soils; at elevations from 2,000 - 3,700 metres in China[].

Properties

Edibility Rating
Medicinal Rating
Habit	Annual
Height	1.20 m
Growth Rate	Fast
Pollinators	Insects
Cultivation Status	Wild

Cultivation Details

Qing Hao is a determinate short-day plant. Non-juvenile plants are very responsive to photoperiodic stimulus and flower about two weeks after induction. The critical photoperiod seems to be about 13.5 hours, but there are likely to be photoperiod x temperature interactions. The plant is not adapted to the tropics because flowering will be induced when the plants are very small[].
An easily grown plant, succeeding in a well-drained circumneutral or slightly alkaline loamy soil, preferring a sunny position[, ]. Plants are longer lived, more hardy and more aromatic when they are grown in a poor dry soil[].
A fast-growing annual plant, it is tall but neat in habit with a handsome fragrant foliage and is useful for filling gaps at the back of a border[].
The plant is extremely vigorous and essentially disease and pest free[].
In Lafayette Indiana, USA (40°21'N) plants flower in early September with mature seeds produced in October[].
Most collections of artemisia derive from natural stands with highly variable artemisinin content, some as low of 0.01%. Selections from Chinese origin vary from 0.05 to 0.21%. Swiss researcher N. Delabays reports a clonal selection derived from Chinese material which produces 1.1% artemisin but is very late flowering; proprietary hybrids have been obtained with somewhat lower content but flower earlier[].
Members of this genus are rarely if ever troubled by browsing deer[].

Edible Uses

An essential oil in the leaves is used as a flavouring in spirits such as vermouth[].

Medicinal

Qing Ho, better known in the West as sweet wormwood, is a traditional Chinese herbal medicine. An aromatic anti-bacterial plant, recent research has shown that it destroys malarial parasites, lowers fevers and checks bleeding[, , ]. It is often used in the Tropics as an affordable and effective anti-malarial[].

The leaves are antiperiodic, antiseptic, digestive, febrifuge[, ]. An infusion of the leaves is used internally to treat fevers, colds, diarrhoea etc[, ]. Externally, the leaves are poulticed onto nose bleeds, boils and abscesses[, ]. The leaves are harvested in the summer, before the plant comes into flower, and are dried for later use[].

The plant contains the essential oil artemisinin, which is well known in Traditional Chinese Medicine for its antiinflammatory, antifebrile and haemostatic properties. Artemisinin has proved to be a dramatically effective anti-malarial agent, effective against multi-drug resistant Plasmodium spp[, , , ]. Clinical trials have shown it to be 90% effective and more successful than standard drugs[]. In a trial of 2,000 patients, all were cured of the disease[].

The seeds are used in the treatment of flatulence, indigestion and night sweats[].

Other Uses

The plant is used in China as a medium for growing Aspergillus which is used in brewing wine.

Artemisinin, a sesquiterpene lactone found in the leaves, has phytotoxic activity and so shows a marked herbicidal activity[, ].

The plant yields 0.3% essential oil[]. This has an agreeable, refreshing and slightly balsamic odour and has been used in perfumery[].

Propagation

Seed - sow spring in a cold frame and plant out in late spring or early summer. Alternatively, the seed can be sown late spring in situ.