Artemisia annua L.

Sweet Wormwood

Artemisia annua plant

Family - Asteraceae/Anthemideae

Stems - Erect, to 2 m, ridged, glabrous, minutely glandular. Plants taprooted annuals.

Leaves - Alternate, to 10 cm. Leaves near base long-petiolate, often withered at flowering. Upper leaves reduced, short-petiolate to sessile. Leaf blades 1-2 times pinnately lobed or compound, ovate in outline, fernlike, the ultimate segments narrow but not threadlike, glabrous, minutely glandular, strongly aromatic.

Artemisia_annua_leaf.jpgLeaf.

Artemisia_annua_leaf2.jpg

Inflorescence - Open, leafy panicles bearing clusters of stalked heads.

Artemisia_annua_inflorescence2.jpgInflorescence branch.

Artemisia_annua_inflorescence.jpg

Flowers - Heads discoid, with the central florets perfect and the marginal florets perfect or pistillate. Involucre 1.0-1.5 mm long, the bracts in 2 or 3 overlapping rows, glabrous but minutely glandular, with broad, thin, transparent margins and tips. Receptacle convex, naked, lacking bristly hairs. Corollas minute (< 1mm). Pappus absent.

Artemisia_annua_heads.jpgHeads.

Fruits - 0.7-0.9 mm long, more or less obovoid, faintly lined, tan to grayish brown, shiny.

Flowering - August - November.

Habitat - Bottomland forests, riverbanks, lake margins, old fields, railroads, open disturbed areas.

Origin - Native to Asia.

Other info. - This plant is most often found along major rivers. When young it can resemble Conium maculatum, having frilly, fernlike foliage, but the intense fragrance of the foliage tells the true identity in an instant. The aroma is the best way I know to identify these plants, at least to genus. Wormwoods have been used to prepare beverages such as absinthe, though some might consider the fragrance more appropriate to perfumery than internal consumption.

Importantly, Artemisia annua has been found effective against malaria, having been used for that purpose in traditional Chinese medicine for centuries. The active constituent is a sesquiterpene lactone known as artemisinin, which has served as a lead compound for further structural manipulation in drug discovery research.

Photographs taken at Klondike County Park, St. Charles County, MO, 7-5-2013, and in Washington Riverfront Park, Franklin County, MO, 9-15-2018 (SRTurner).



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