wormwood, Mediterranean perennial herb or shrubby plant ( Artemisia absinthium ) of the family Asteraceae (aster family), often cultivated in gardens and found as an escape in North America. It has silvery gray, deeply incised leaves and tiny yellow flower heads. Wormwood oil has been utilized since ancient times as an insect repellent, particularly for moths; until recently it was used for intestinal worms and for other medicinal purposes. It was also employed in brewing but is best known for its bitter principle, which is an important ingredient of absinthe; the compound alpha-thujone, found in wormwood, formerly gave that liqueur its toxicity. Because of its bitter taste the common wormwood has long symbolized human rancor and is often so represented in the Bible.
Other artemisias, some American, are also called wormwood; still others include southernwood ( A. abrotanum ), tarragon, silver king artemisia ( A. albula ), old woman, or dusty miller ( A. stelleriana ), Roman wormwood ( A. pontica ), sagebrush, sweet, or Chinese, wormwood ( A. annua ), from which the antimalarial artemisinin is extracted, and Levant wormseed ( A. cina ), which yields santonin. Artemisias are classified in the division Magnoliophyta, class Magnoliopsida, order Asterales, family Asteraceae.