Ambrosia psilostachya

western ragweed, cuman ragweed, perennial ragweed


Leaf Arrangement


Leaf Attachment


Leaf Margin

pinnatifid, toothed

Leaf Type


Growth Form


Flower Color

green, yellow

Flower Month


Height (meters)

0.3 - 1.0

Milky Sap








Growing Season

Warm season

Wetland Class


Wetland Coefficient of Conservatism


Prairie Coefficient of Conservatism


Field Characters

Ambrosia psilostachya is similar to A. artemisiifolia but its leaves are only once-pinnately divided, while those of A. artemisiifolia are twice-pinnate. Difficult to pull up, attached to underground rhizome.

Cultural Information

This species in invasive in new planting and can displace native perennial seedlings. Care should be taken to avoid contamination of planted seed with this noxious weed. When growing conditions are right, this weedy pest can produce 6 or more shoots from one underground stem, spreading rapidly. It grows on a variety of soils through the U.S. but is more abundant on the plains and prairies of the Midwest. It is often treated with chemicals for control but is not thought to compete well with vigorous grasses in well managed range.

Animal Use

Very unpalatable to cattle. A high-use forage plant for white-tail deer in spring and summer. Deer also eat giant ragweed. Ragweed seeds are one of the most important quail foods based on volume consumed. The following Information is for the genus Ambrosia with notation that A. artemisiifolia and A. psilostachya are the most useful to wildlife while A. trifida is of little value: Animals that eat its seeds: Yellow rail, Wilson snipe, Ground dove, Mourning dove, Attwater's prairie chicken, Bobwhite quail, Wild turkey, Woodcock, Redwing blackbird, Cardinal, Purple finch, Eastern goldfinch, Chipping sparrow, English sparrow, Harris sparrow, Eastern lark sparrow, Lincoln sparrow, Savannah sparrow, Tree sparrow, Eastern vesper sparrow, White-crowned sparrow, Meadow mouse, and White-tailed deer. Animals that eat its foliage: White-tailed deer and cottontail rabbit (Martin et al. 1951).

Natural History

A warm-season perennial which reproduces by seed and long, slender rootstocks. The male flowers are nodding and are borne in clusters on the upper part of the flowering stalks, while the female flowers appear inconspicuously near the base of the flowering stalks in the axils of the upper leaves. The dark colored seeds are 1/8" long and are covered with a distinctive woody hull with a pointed tip surrounded by sharp spines. It is unpalatable to livestock but is sometimes eaten when better forage is not available. It is one of a group of weeds that when grazed by milk cows, will give the milk a bitter taste. This is the most wide spread of ragweeds and is the principal source of allergenic pollen in the central U.S.