Ambrosia psilostachya is a species of ragweed known by the common names Cuman ragweed, perennial ragweed, and western ragweed.
It is native to most of North America including all of southern Canada, nearly all of the continental United States, and the northern half of Mexico.  It is a common plant in many habitat types, including disturbed areas such as roadsides.
Ambrosia psilostachya is an erect perennial herb growing a slender, branching, straw-colored stem to a maximum height near two meters, but more often remaining under one meter tall. Leaves are up to 12 centimeters long and vary in shape from lance-shaped to nearly oval, and they are divided into many narrow, pointed lobes. The stem and leaves are hairy.
The top of the stem is occupied by an inflorescence which is usually a spike. The species is monoecious, and the inflorescence is composed of staminate (male) flower heads with the pistillate heads located below and in the axils of leaves.
The pistillate heads yield fruits which are achenes located within oval-shaped greenish-brown burs about half a centimeter long. The burs are hairy and sometimes spiny. The plant reproduces by seed and by sprouting up from a creeping rhizome-like root system.
- Medicinal uses
- USDA . accessed 2.14.2013
- University of Michigan - Dearborn; Native American Ethnobotany — Ambrosia psilostachya . accessed 2.14.2013
- USDA Plants Profile for Ambrosia psilostachya (Cuman ragweed)
- Jepson Manual Treatment: Ambrosia psilostachya
- FEIS Ecology
- USGS Northern Prairie Wildlife Profile
- Ambrosia psilostachya Photo gallery
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