Ambrosia trifida Pages

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W. J. Beal Botanical Garden Of interest this week at Beal... Giant Ragweed Ambrosia trifida Family: the Sunflower family, Asteraceae. Also called Great ragweed, Tall ambrosia, Bloodweed, Blood ragweed, Buffalo weed, Horse cane, Bitterweed Giant ragweed, Ambrosia trifida, is a common, if not entirely welcome site at road edges and waste places throughout most of the United States (ours is in bed 64). Today, its membership in the genus Ambrosia, the ragweeds, and their associations with hay fever suffering make this weed unpopular; a fallen ghost of its former glory as an Indigenous North American food and tool resource plant. Caches of giant ragweed seeds from Colorado and elsewhere make it clear that Indigenous Americans found this a useful plant. Recently, some archaeologists have suggested that giant ragweed was used in arrow shafts, but that the seeds were impractical as a food source. However, the fact that Indigenous Americans were specialists at navigating starvation episodes, combined with the observation that giant ragweed seeds are comprised of about 19 percent edible oil, make it fairly certain that these seeds would not be overlooked as a food resource. Ambrosia trifida, is the tallest of the ragweeds (genus Ambrosia) reaching some 12 to 14 feet (3.6 to 4.3 meters) in height. The ragweeds broadcast their highly allergenic pollen grains from erect male flower spikes. The female seed-bearing flowers are produced near the bases of the male inflorescences, in rather leafy burr-like knots. This characteristic serves to distinguish Ambrosia from plants in the genus Iva that bear both sexes of flowers from the same flower heads. Giant ragweed is an aggressive large-scale weed. This feathery giant may forest the margins of commercial fields where they lower yields somewhat, probably due to nutrient competition with the crops. Giant ragweed, as with all ragweeds, is native to the Americas. But as a weed, it has been successful on all the temperate continents. It is noted as a major invasive weed of northeastern China.

Transcript of Ambrosia trifida Pages

Page 1: Ambrosia trifida Pages

W. J. BealBotanical Garden

Of interest this week at Beal...

Giant RagweedAmbrosia trifidaFamily: the Sunflower family, Asteraceae.Also called Great ragweed, Tall ambrosia, Bloodweed, Bloodragweed, Buffalo weed, Horse cane, Bitterweed

Giant ragweed, Ambrosia trifida, is a common, if not entirely welcome site at road edges and waste places throughout most of the United States (ours is in bed 64). Today, its membership in the genus Ambrosia, the ragweeds, and their associations with hay fever suffering make this weed unpopular; a fallen ghost of its former glory as an Indigenous North American food and tool resource plant. Caches of giant ragweed seeds from Colorado and elsewhere make it clear that Indigenous Americans found this a useful plant. Recently, some archaeologists have suggested that giant ragweed was used in arrow shafts, but that the seeds were impractical as a food source. However, the fact that Indigenous Americans were specialists at navigating starvation episodes, combined with the observation that giant ragweed seeds are comprised of about 19 percent edible oil, make it fairly certain that these seeds would not be overlooked as a food resource.

Ambrosia trifida, is the tallest of the ragweeds (genus Ambrosia) reaching some 12 to 14 feet (3.6 to 4.3 meters) in height. The ragweeds broadcast their highly allergenic

pollen grains from erect male flower spikes. The female seed-bearing flowers are produced near the bases of the male inflorescences, in rather leafy burr-like knots. This characteristic serves to distinguish Ambrosia from plants in the genus Iva that bear both sexes of flowers from the same flower heads.

Giant ragweed is an aggressive large-scale weed. This feathery giant may forest the margins of commercial fields where they lower yields somewhat, probably due to nutrient competition with the crops. Giant ragweed, as with all ragweeds, is native to the Americas. But as a weed, it has been successful on all the temperate continents. It is noted as a major invasive weed of northeastern China.

Page 2: Ambrosia trifida Pages

Giant ragweed also constitutes one of the larval food plants of the attractive and polymorphic nymphalid butterfly called the bordered patch, Chlosyne lacinia. Its range includes much of the south central United States and its food plants include several other members of the family Asteraceae, especially wild sunflower, Helianthus annuus.

The leaves have medicinal traditions that include its uses as an astringent, emetic, and febrifuge. There is evidence that its seeds heads and sap have histories as a red dye. Experiments with the steam-extracted essential oils have shown possibly useful antimicrobial and antifungal properties that have spurred some authors to suggested that the essential oils of giant ragweed are appropriate for commercial development. In North America, the leaves of giant ragweed have also been used to treat a variety of insect bites and skin complaints.

Staminate and pistillateflowers are borne separately on the branches of Giant ragweed, Ambrosia trifida.

Male flower spike

Female flower

Bracts surrounding the seed-producing flowers

Seed