Ambrosia psilostachya is a species of ragweed known by the common names Cuman ragweed and perennial ragweed, and western ragweed.
Distribution and habitat The plant is widespread across much of North America (United States, Canada, and northern Mexico).Biota of North America Program 2104 county distribution map It is also naturalized in parts of Europe, Asia, Australia, and South America.United States Department of Agriculture Plants Profile . accessed 2.14.2013 It is a common plant in many habitat types, including disturbed areas such as roadsides.Flora of North America Vol. 21 Page 18 Ambrosia psilostachya de Candolle in A. P. de Candolle and A. L. P. P. de CandolleFlora of China Vol. 20-21 Page 877 裸穗豚草 luo sui tun cao Ambrosia psilostachya CandolleTropicos, specimen listing for Ambrosia psilostachya DCAltervista Flora Italiana, Ambrosia con spighe rade, Ambrosia psilostachya DC. includes photos and European distribution mapAtlas of Living Australia, Ambrosia psilostachya DC. Perennial Ragweed
Description 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. This bloom period is from June through November.
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.
Ecology Ambrosia psilostachya is a host plant for the caterpillars of Bucculatrix transversata, Cosmopterix opulenta, Exaeretia gracilis, Gnorimoschema saphirinella, Schinia sexplagiata; the beetles Calligrapha disrupta, Calligrapha suturalis; and the grasshopper Spharagemon collare.
Medicinal uses This plant had a number of medicinal uses among several different Native American tribes, including the Cheyenne, Kumeyaay (Diegueno), and Kiowa people. University of Michigan at Dearborn: Native American Ethnobotany of Ambrosia psilostachya . accessed 2.14.2013
Chemistry Ambrosia psilostachya contains a group of phytochemicals called psilostachyins.
References
External links Calflora Database: Ambrosia psilostachya (Western ragweed) Jepson Manual eFlora (TJM2) treatment: Ambrosia psilostachya USDA National Forest Service, FEIS Ecology of Ambrosia psilostachya USGS.gov: Northern Prairie Wildlife Profile UC Calphotos Photos gallery of Ambrosia psilostachya