''Ambrosia dumosa'', the burro-weed or white bursage, a

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 ...

n species of plants in the family

Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...

. It is a common constituent of the creosote-bush scrub community throughout the

Mojave desert The Mojave Desert ( ; mov, Hayikwiir Mat'aar; es, Desierto de Mojave) is a desert in the rain shadow of the Sierra Nevada mountains in the Southwestern United States. It is named for the indigenous Mojave people. It is located primarily in ...

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

Nevada Nevada ( ; ) is a U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. N ...

, and

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

and the

Sonoran Desert The Sonoran Desert ( es, Desierto de Sonora) is a desert in North America and ecoregion that covers the northwestern Mexican states of Sonora, Baja California, and Baja California Sur, as well as part of the southwestern United States (in Arizona ...

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

and northwestern

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 ...

(

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

Baja California Sur Baja California Sur (; 'South Lower California'), officially the Free and Sovereign State of Baja California Sur ( es, Estado Libre y Soberano de Baja California Sur), is the least populated state and the 31st admitted state of the 32 federal ent ...

Sonora Sonora (), officially Estado Libre y Soberano de Sonora ( en, Free and Sovereign State of Sonora), is one of the 31 states which, along with Mexico City, comprise the Administrative divisions of Mexico, Federal Entities of Mexico. The state is d ...

, Chihuahua).Flora of North America Vol. 21 Page 13 Bursage Ambrosia dumosa (A. Gray) W. W. Payne, J. Arnold Arbor. 45: 422. 1964.
/ref>Tropicos, specimen listing for ''Ambrosia dumosa'' (A. Gray) W.W. Payne
/ref> ''Ambrosia dumosa'' has been studied to determine

allelopathic Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the germination, growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have ben ...

interactions with creosote bush, ''

Larrea tridentata ''Larrea tridentata'', called creosote bush and greasewood as a plant, chaparral as a medicinal herb, and ''gobernadora'' (Spanish language, Spanish for "governess") in Mexico, due to its ability to secure more water by inhibiting the growth of n ...

'', which produces a chemical that inhibits the growth of ''A. dumosa.'' Other studies have suggested that ''A. dumosa'' roots produce a chemical that causes them to grow away from conspecific roots, preventing competition for water resources. In addition to burro-weed, ''A. dumosa'' is also commonly called white bursage, and burrobush.

Description

''Ambrosia dumosa'', a form of ragweed, is a highly branched shrub 20 to 90 cm in height. The younger stems are covered with soft gray-white hairs. Approximately

obovate The following is a list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). The edge of the leaf may be regular o ...

leaves are 1 to 3 times

pinnately Pinnation (also called pennation) is the arrangement of feather-like or multi-divided features arising from both sides of a common axis. Pinnation occurs in biological morphology, in crystals, such as some forms of ice or metal crystals, and in ...

compound Compound may refer to: Architecture and built environments * Compound (enclosure), a cluster of buildings having a shared purpose, usually inside a fence or wall ** Compound (fortification), a version of the above fortified with defensive struct ...

or deeply

lobed The following is a list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). The edge of the leaf may be regular o ...

and generally clustered on short branches. The leaves are 0.5 to 4 cm long and also covered in soft gray-white hairs. Its inflorescence is yellow with

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 ...

and

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 of a flower; it consists of (one or more) ''pistils'' ...

headson a single plant (

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 ...

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 ...

heads A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may no ...

have many flowers and are 3 to 5 mm in diameter with a 5 to 8 lobed

involucre In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or o ...

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 of a flower; it consists of (one or more) ''pistils'' ...

are 2 flowered and lack corollas. ''Ambrosia dumosa'' has spherical bur-like fruits ranging in color from golden to purple to brown. Along with microscopic hairs, the fruit has 12 to 35 flat and straight spines which are 5 to 9 mm in length and scattered over the surface.Allen A.Schoenerr, Allen A. 1992. ''A Natural History of California''. Berkeley: University of California Press. ''Ambrosia dumosa'' becomes dormant during drought, losing all of its leaves to prevent water loss by transpiration;

drought deciduous Drought deciduous, or drought semi-deciduous plants refers to plants that shed their leaves during periods of drought or in the dry season. This phenomenon is a natural process of plants and is caused due to the limitation of water around the env ...

. During this time, it can still be recognized by the presence of longitudinal stripes on smaller stems. Like other types of Ambrosia, this is a ragweed, wind-blown pollen from burro-weed can cause serious allergic reactions. Increasing cases in Mojave Desert as the population grows from Joshua Tree, CA to Las Vegas, NV.

References

Jepson Manual Treatment: ''Ambrosia dumosa''
*C.Michael Hogan, species editor. 2010
''Ambrosia dumosa''. Encyclopedia of Life

External links

Jepson Manual Treatment: ''Ambrosia dumosa''Lady Bird Johnson Wildflower Center Native Plant Information Network (NPIN), University of Texas

''Ambrosia dumosa'' — Calphotos Photo gallery, University of California
* {{Taxonbar, from=Q459410 dumosa North American desert flora Flora of the Southwestern United States Flora of Northwestern Mexico Flora of the California desert regions Flora of the Great Basin Flora of the Sonoran Deserts Natural history of the Colorado Desert Natural history of the Mojave Desert Taxa named by Asa Gray Flora without expected TNC conservation status