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Annual Wormwood

Contributor: Jules Janick

Copyright © 1995. All Rights Reserved. Quotation from this document should cite and acknowledge the contributor.

  1. Common Names
  2. Scientific Names
  3. Uses
  4. Origin
  5. Crop Status
    1. Toxicities
    2. Traditional Medicinal Uses
  6. Botany
    1. Taxonomy
    2. Morphology and Floral Biology
    3. Ecology
    4. Secondary Metabolites
  7. Crop Culture (Horticulture)
  8. Horticulture
    1. In vitro Production
    2. Field Production
  9. Germplasm
  10. Key References
  11. Selected Experts

Common Names

English: annual wormwood, sweet annie, sweet wormwood
Chinese: qinghao

Scientific Names

Species: Artemisia annua L.
Family: Asteraceae (Compositae)

Uses

Used in the crafting of aromatic wreaths, as a flavoring for spirits such as vermouth, as a source of essential oils, and as a source of artemisinin (qinghausu), an important natural antimalarial effective against multi-drug resistant Plasmodium spp.

Origin

Annual herb native to Asia, most probably China. Occurs naturally as part of a steppe vegetation in the northern parts of Chahar and Suiyuan provinces in China, at 1000 to 1500 m above sea level. Now naturalized in many countries including the United States.

Crop Status

An annual crop cultivated in China and Vietnam as a source of artemisinin. Cultivated in Romania as a source of essential oils. Cultivated on small scale is the United States as a source of aromatic wreaths.

Toxicities

Unknown but pollen is extremely allergenic. Likely to be toxic as are other members of the genus.

Traditional Medicinal Uses

Used traditionally in China to treat fevers and hemorrhoids.

Botany

Taxonomy

Artemisia belongs to the tribe Anthemideae of the Asteroideae, a subfamily of the Asteraceae. Various taxonomic treatments subdivide genus Artemisia into various subgeneric sections; A. annua has been considered in the subsection Absinthium (Hall and Clements 1923) or in a combined subsection Artemisia (Absinthium + Abrotanum). (Poljakov 1961, Yeou-ruenn 1994).

Morphology and Floral Biology

A. annua is a large shrub often reaching more than 2.0 m in height, usually single-stemmed with alternate branches. The aromatic leaves are deeply dissected and range form 2.5 to 5 cm in lengh. Leaves contain both 10-celled biseriate trichomes and 5 cell filamentous (T) trichomes.

The nodding flowers (capitula), only 2 to 3 mm in diameter, are greenish-yellow enclosed by numerous, imbricated bracts. Capitula are displayed in loose panicles containing numerous central bisexual florets and marginal pistillate florets, the latter extruding stigmas prior to the central flowers. Both flowers have synpetalous tubular corolla with the top split into five lobes in the hermaphroditic florets and 2-3 lobes in the pistillate florets. The receptacle is glabrous, not chaffy, and triangular in shape. Both florets and receptacle bear abundant 10-celled biseriate trichomes; T-trichomes (filamentous) occur at the pedicel and bracts. The biseriate glandular trichomes sequester artemisinin.as well as highly aromatic volatile oils (essential oils).

Ecology

A. annua 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. In Lafayette Indiana, USA (40°21'N) plants flower in early September with mature seeds produced in October. The plant is unadapted to the tropics because flowering will be induced when the plants are very small.

Secondary Metabolites

Biseriate glandular trichomes are the source of highly aromatic volatile oils, mainly artemisia ketone, 1.8-cineole camphor; germacrene D, camphene hydrate, and alpha-pinene; beta-caryophyllene, myrcene, and artemisia alcohol. Nonvolatile sesquiterpenes can be recovered from the plant by solvent extraction, some of which show high antimalarial activity. There are at least 20 known sesquiterpenes including artemisinin (arteannuin A), arteannuin B, artemisitene, and artemisinin acid.

Crop Culture (Horticulture)

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.

Horticulture

In vitro Production

A. annua is easily propagated in vitro by standard protocols. Cytokinins increase shoot proliferation but decrease rooting and increase vitrification. A. annua can be grown and propagated by microcuttings in a hormone-free medium. Artemisinin is produced in shoots in vitro and is enhanced by the presence of roots. None or trace levels of artemisinin are found in roots, callus, cells, or cell free medium. There is no evidence that in vitro production of artemisinin will be commercially feasible.

Field Production

Field production of A. annua is presently the only commercially viable method to produce artemisinin because the synthesis of the complex molecule is uneconomic. Because of the low levels of artemisin in leaves and inflorescence and early flowering caused by short days, high biomass production will be required to make production in the tropics economic. The most important management problems will be to achieve uniform stands and weed control. The plant is extremely vigorous and essentially disease and pest free. Most researchers transplant seedlings but direct seeding will be required for commercial production.

Germplasm

Various specialty herb seed sources sell A. annua seed for the wreath market. (See S. Facciola, l990. Cornucopia: A source book of edible plants Kampong Publications. Vista, California)

Indiana Center for New Crops. Horticulture Bldg 1165, Purdue University, West Lafayette, IN 47906-1165 has small amounts of seed for distribution.

Key References

Selected Experts

N. Delabays
Mediplant
Centre de Recherches sur les Olantes Medicinales et Aromatiques
Centre des Fouger CH
1964 Conthey, Switzerland
Tel 027 -362722
Fax 027 363017

Jorge F.S. Ferreira
USDA-ARS
1224 Airport Rd.
Beaver, WV 25813
(304) 256-2827
jorge.ferreira@ars.usda.gov

Jules Janick
Purdue University
1165 Horticulture Building
West Lafayette, Indiana 47907-1165
tel 765 494 1329
fax 765 494 0391
janick@purdue.edu

J.C. Laughlin
1/14A Sherburd Street
Kingston, Tasmania 7050, Australia
Tel./Fax 61-3-62271263

James E. Simon
Cook/NJAES at Rutgers
Plant Science
59 Dudley Road
New Brunswick, NJ 08901
(732) 932-9711 EXT: 355
jesimon@aesop.rutgers.edu

Herman J. Woerdenbag
Dept. of Pharmaceutical Biology
University Centre for Pharmacy
University Groningen, Antonius
Deusinglaan 2, 9713 AW
Groningen, The Netherlands

Contributor: Jules Janick, Center for New Crops & Plant Products, Purdue University

Copyright © 1995. All Rights Reserved. Quotation from this document should cite and acknowledge the contributor.