SafePlants

Giant Ragweed (Ambrosia trifida)

Giant ragweed, scientifically known as Ambrosia trifida, is a prevalent flowering plant belonging to the sunflower family (Asteraceae). It is native to North America and recognized for its allergenic pollen.

Considerations for Pets

• The text mentions the presence of hairs on the green stems.
• Ragweed's pollen is an allergen, which might also affect certain pets.

Considerations for Children

• The text mentions the presence of hairs on the green stems.
• Ragweed's pollen is an allergen, which might affect children.

Taxonomy and Nomenclature

• Scientific Name: Ambrosia trifida L.
• Family: Asteraceae (also known as Compositae or Aster Family)
• Common Names: Giant Ragweed, Great Ragweed, Texan Great Ragweed, Bitterweed, Bloodweed, Buffalo Weed, Horse Cane, Kinghead, Tall Ragweed, Horseweed.
• Synonyms: The text refers to "Great Ragweed Ambrosia trifida Linnaeus var. trifida" suggesting that other varieties or subspecies might exist.

Distribution and Habitat

• Giant ragweed is indigenous to North America.
• It is widespread in Canada and can be found in every state in the continental U.S. except Nevada.
• It commonly forms large stands in disturbed areas, such as streambanks.
• It can be found in fields, gardens, and roadsides.

Ecological Role

• Giant ragweed can be invasive, particularly in disturbed areas.
• It is listed as a noxious weed in California and is considered weedy in many areas.
• It can negatively affect crops, causing reduced yields.

Morphological Characteristics

• Giant ragweed is a summer annual that grows from 3 to 12 feet tall, branching occasionally.
• The green stems are covered with white hairs.
• Leaves are opposite.
• It has 3 to 8 inch spike-like racemes of 1/8-inch yellow to greenish, short-stalked, petal-less flowers.
• Some leaves are deeply and palmately three-cleft.

Quirky Facts

• The genus name Ambrosia comes from the Greek word for the food of the gods. Quite ironic, considering the plant's allergenic properties.
• Giant ragweed leaves, when they first appear, can be mistaken for sunflower or sunchoke leaves.

Interactions with Other Organisms

• Pollen from giant ragweed contains many antigens that cause hay fever in humans.
• It is wind-pollinated.
• The leaves of common ragweed can impart a bitter taste to milk if eaten by cattle.

Herbicide Resistance

• Giant ragweed is becoming immune to herbicides, particularly glyphosate, posing a challenge to farmers.

Further Information

• Dave's Garden: A community for sharing gardening tips and ideas.
• Purdue Extension: Offers information on the biology and management of giant ragweed.
• Nature Manitoba: Provides information on Great Ragweed (Ambrosia trifida).
• Bioimages at Vanderbilt: Contains images of Great Ragweed. http://bioimages.vanderbilt.edu/thomas/0365-02.htm