Giant (Tall) Ragweed

WEEDS

GENUS/SPECIES

Ambrosia trifida

FAMILY

Asteraceae
(Compositae)

SYNONYMS

Information not available

DISTRIBUTION

Eastern two-thirds of US

Central Montana eastward to Maine
Maine southward to NW Florida
Florida westward to W Texas
W Texas N to central Montana
Additional population in SE Arizona

Human Product Number - 55

Veterinary Product Number - 55

Comments

This impressive native annual weed can grow to be over 13 feet tall. It is especially abundant in wet areas such as sandbars along rivers. The larger leaves usually have 3 points, occasionally five. The plant blooms in late summer and early autumn. The numerous male flowers, which produce copious pollen, are along spikes found at the top of each branch. There are relatively few female flowers that are inconspicuous and found below the male. Allergenically, it is highly cross-reactive with short ragweed.