SafePlants

Annual Ragweed (Ambrosia artemisiifolia)

Annual ragweed, scientifically known as Ambrosia artemisiifolia, is also commonly referred to as ambrosia, horseweed, asthma plant, fever weed, bitterweed, wild tansy, blackweed, common ragweed, low ragweed, Roman wormwood, and hogweed.

Considerations for Pets

• This plant is often found in disturbed sites and pastures.

Considerations for Children

• This plant is often found in disturbed sites and pastures.

Taxonomy and Nomenclature

• Scientific Name: Ambrosia artemisiifolia L.
• Family: Asteraceae (also known as the composite or daisy family)
• Synonyms:
  • Ambrosia artemisiifolia var. elatior
  • Ambrosia artemisiifolia var. paniculata
  • Ambrosia elatior
  • Ambrosia artemisiifolia syn A elatior

Distribution and Habitat

• Native to eastern North America, and is the most widespread plant of the genus Ambrosia in North America, most prevalent in eastern and north central States.
• It is an introduced weed that invades roadsides, wastelands, and poor or overgrazed pastures.
• It is spreading rapidly in south-east Queensland, Australia, and is now widespread.

Ecological Role

• It is considered a significant weed, particularly in Queensland, Australia, where it is a declared pest under legislation.
• It is an invasive plant in Europe.

Morphological Characteristics and Growth Habits

• It is an erect annual herb, typically growing to 0.5-2 meters tall, but can reach up to 3.5 meters in rare cases.
• It has a shallow, fibrous root system.
• The leaves are grey-green, hairy, and variable in shape; lower leaves are ovate to lanceolate, with blades up to 16 cm long.
• It is a much-branched plant along a somewhat hairy stem.
• The plant has a ragged appearance.
• Leaves are usually 4-10 cm long, hairy on top, and rounded.

Quirky Facts

• The name "asthma plant" is associated with Annual Ragweed.