''Ambrosia psilostachya'' is a species of

ragweed Ragweeds are flowering plants in the genus ''Ambrosia'' in the aster family, Asteraceae. They are distributed in the tropical and subtropical regions of the Americas, especially North America,North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

(

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

, and northern

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

). It is also naturalized in parts of

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

, and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

. 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 Candolle
/ref>

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 An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...

which is usually a spike. The species is

monoecious Monoecy (; adj. monoecious ) is a sexual system in seed plants where separate male and female cones or flowers are present on the same plant. It is a monomorphic sexual system alongside gynomonoecy, andromonoecy and trimonoecy. Monoecy is conne ...

, and the inflorescence is composed of

staminate The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filam ...

(male) flower heads with the

pistillate Gynoecium (; ) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl (botany), whorl of a flower; it consists of (one or m ...

heads located below and in the axils of leaves. This bloom period is from June through November. The pistillate heads yield fruits which are

achene An achene (; ), also sometimes called akene and occasionally achenium or achenocarp, is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate (formed from one carpel) and indehiscent (they do not ope ...

s 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 ''Bucculatrix transversata'' is a moth in the family Bucculatricidae. It is found in North America, where it has been recorded from California. The species was first described in 1910 by Annette Frances Braun. The wingspan is about 7 mm. The ...

'', '' Cosmopterix opulenta'', '' Exaeretia gracilis'', '' Gnorimoschema saphirinella'', ''

Schinia sexplagiata ''Schinia sexplagiata'' is a moth of the family Noctuidae. It is found in western North America, east up to west Texas. The wingspan is about 21 mm. The larvae feed on ''Ambrosia psilostachya ''Ambrosia psilostachya'' is a species of ...

''; the beetles '' Zygogramma disrupta'', '' Zygogramma 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 The Cheyenne ( ) are an Indigenous people of the Great Plains. Their Cheyenne language belongs to the Algonquian language family. Today, the Cheyenne people are split into two federally recognized nations: the Southern Cheyenne, who are enroll ...

, Kumeyaay (Diegueno), and

Kiowa people Kiowa () people are a Native American tribe and an indigenous people of the Great Plains of the United States. They migrated southward from western Montana into the Rocky Mountains in Colorado in the 17th and 18th centuries,Pritzker 326 and eve ...

Chemistry

''Ambrosia psilostachya'' contains a group of

phytochemical Phytochemicals are chemical compounds produced by plants, generally to help them resist fungi, bacteria and plant virus infections, and also consumption by insects and other animals. The name comes . Some phytochemicals have been used as poisons ...

s called psilostachyins.

References

External links

Calflora Database: ''Ambrosia psilostachya'' (Western ragweed)Jepson Manual eFlora (TJM2) treatment: ''Ambrosia psilostachya''
* ttps://web.archive.org/web/20080916225004/http://www.npwrc.usgs.gov/resource/plants/wildflwr/species/ambrpsil.htm USGS.gov: Northern Prairie Wildlife Profilebr>UC Calphotos Photos gallery of ''Ambrosia psilostachya''
{{Taxonbar, from=Q3613854 psilostachya Flora of Canada Flora of Northeastern Mexico Flora of Northwestern Mexico Flora of the Eastern United States Flora of the Western United States Plants described in 1836 Taxa named by Augustin Pyramus de Candolle Natural history of the California chaparral and woodlands Plants used in traditional Native American medicine Flora without expected TNC conservation status