Ambrosia psilostachya is a species of ragweed known by the common names Cuman ragweed and perennial ragweed,[3] and western ragweed.

Ambrosia psilostachya
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Asterids
Order:	Asterales
Family:	Asteraceae
Genus:	Ambrosia
Species:	A. psilostachya
Binomial name
Ambrosia psilostachya DC.
Synonyms[1]
Ambrosia californica Rydb. Ambrosia coronopifolia Torr. & A.Gray Ambrosia hispida Torr. Ambrosia lindheimeriana Scheele Ambrosia peruviana DC. 1836 not All. 1773 nor Willd. 1805[2] Ambrosia rugelii Rydb.

Distribution and habitat

The plant is widespread across much of North America (United States, Canada, and northern Mexico).[4] It is also naturalized in parts of Europe, Asia, Australia, and South America.[5] It is a common plant in many habitat types, including disturbed areas such as roadsides.[6][7][8][9][10]

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.[6]

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.[6] 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.[11]

Ecology

Ambrosia psilostachya is a host plant for the caterpillars of Bucculatrix transversata,[12] Cosmopterix opulenta, Exaeretia gracilis, Gnorimoschema saphirinella,[13] Schinia sexplagiata; the beetles Zygogramma disrupta, Zygogramma suturalis;[14] and the grasshopper Spharagemon collare.[15]

Medicinal uses

This plant had a number of medicinal uses among several different Native American tribes, including the Cheyenne, Kumeyaay (Diegueno), and Kiowa people.[16]

Chemistry

Ambrosia psilostachya contains a group of phytochemicals called psilostachyins.[17]

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

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