Carnegiea gigantea, Giant Saguaro

Southwest Desert Flora

Home to the plants of the Sonoran, Chihuahuan and Mojave Deserts

Cirsium ochrocentrum, Yellowspine Thistle

Ambrosia monogyra, Singlewhorl Burrobrush

Singlewhorl Burrobrush has both male and female flowers in the same clusters. Flowers are white or green and most flowers are males. Here are male (staminate) flowers, most buds with just a few fully opened. Ambrosia monogyra Singlewhorl Burrobrush has both male and female flowers in the same clusters. Flowers are white or green and most flowers are males. Here is a small cluster of female (pistillate) flowers recently opened. Ambrosia monogyra Singlewhorl Burrobrush is a shrub or subshrub, new plants green older plants brown or straw colored. Plants are mostly erect and densely branched somewhat broom-like in profile. Note the female flowers in the photograph. Ambrosia monogyra Singlewhorl Burrobrush is a native perennial species that grows in mostly sandy soils especially near rivers or dry river beds. This species grows up to 12 feet in elevations from 1,000 to 4,000 feet. Plants bloom from September to October. Ambrosia monogyra Singlewhorl Burrobrush has green, alternate leaves with rough hairs, threadlike or linear. Plants bloom in the fall from September to October. Plants in the genus Ambrosia are referred to as Ragweed. This species was formerly included in the genus Hymenoclea. Ambrosia monogyra

Scientific Name: Ambrosia monogyra
Common Name: Singlewhorl Burrobrush

Also Called: Burrobrush, Burrobush, Cheeseweed Burrobrush, Needle-Leaf Burrobush, Singlewhorl Burrobush; (Spanish: Jécota, Jejego, Romerillo).

Family: Asteraceae, Sunflower Family
Synonyms: (Hymenoclea monogyra)

Status: Native

Duration: Perennial.

Size: 1 to 5 feet (30-150 cm) tall, or more (12 feet, 370 cm).

Growth Form: Shrub; plants erect; stems and branches slender, branching above; new stems light green, plants, plants dark brown, brown or straw colored.

Leaves: Green; alternate along stems; leaves without stem or stalk (sessile); leaves sparse, drought-deciduous; blades filiform, narrow or linear; new leaves may be pinnately divided into segments, or may also be described as having filiform-lobes; lower surface of leaves smooth (glabrous) or becoming smooth (glabrescent), upper surfaces leaves grooved and minutely covered with minute soft white hairs (puberulous)

Flower Color: White or green; numerous flowers, male (staminate) and female (pistillate) florets in separate heads, the male flowers have translucent white corollas clustered in leaf axils, the female flowers, also clustered in axils, are rounded fruit-bearing structures; all florets without ray flowers (discoid); female heads 1-flowered; fruit spindle shaped bur with a distinctive whorl of papery bract wings around the middle.

Flowering Season: (May) August or September to October or November

Elevation: 1,000 to 4,000 feet (305-1,200 m); below 1,640 feet (500 m) in California.

Habitat Preferences: Mostly sandy soil, desert washes, ravines, floodplains, and along arroyos.

Recorded Range: Singlewhorl Burrobrush is found in the southwest United States in AZ, CA, NM, NV and TX. In the states outside of Arizona it has erratic distribution apparently based on specific habitat requirements. It is marginal in NV. It is also native to Baja California and northwest Mexico (Chihuahua, Sinaloa, Sonora). In Arizona it is locally common where found in the central, southern and western parts of the state.

North America & US County Distribution Map for Ambrosia monogyra (as Hymenoclea monogyra).

North America species range map for Ambrosia monogyra:
North American range map courtesy of Virginia Tech, Dept. of Forest Resources & Environmental Conservation

North America species range map for Ambrosia monogyra: Click image for full size map
Click image for full size map

U.S. Weed Information: Unknown
Invasive/Noxious Weed Information: Unknown

Wetland Indicator: In North America Ambrosia monogyra has the following wetland designations:
Arid West, UPL; Great Plains, FACU; Western Mountains, Valleys, and Coast, UPL.
UPL = Obligate Upland, almost never occur in wetlands;
FACU = Facultative Upland, usually occur in non-wetlands, but may occur in wetlands.

Threatened/Endangered Information: Listed in California as possibly threatened by of trail maintenance and non-native plants.

Genus Information: In North America there are 25 species and 25 accepted taxa overall for Ambrosia. Worldwide, The Plant List includes 51 accepted species names and a further 81 scientific names of infraspecific rank for Ambrosia.

The genus Ambrosia was published by Carl Linnaeus in 1753.

In the Southwestern United States: Arizona has 15 species of genus, California has 14 species, Nevada and New Mexico each have 8 species, Texas and Utah each have 10 species. Data includes Hymenoclea. All data approximate and subject to revision.

Comments: Singlewhorl Burrobrush is a "Burrobrush" that blooms profusely in the fall. It flourishes on disturbance created by occasional floods and its seeds are distributed by flooding.

It is closely related to Cheesebush, Ambrosia salsola which also blooms profusely but in the spring and is much shorter, less than 3 feet (1 m) tall. Pollen from both species causes hay fever in susceptible individuals. A predominate species where found in Arizona however, in California it is listed as threatened because of trail usage and non-native plants. In appearance it is an unlikely member of the daisy family.

Also see in Southwest Desert Flora; Canyon Ragweed, Ambrosia ambrosioides, Triangle-leaf Bursage, Ambrosia deltoidea, White Bursage, Ambrosia dumosa Hollyleaf Bursage, Ambrosia eriocentra, and Cheesebush, Ambrosia salsola.

Importance to Wildlife, Birds and Livestock
Seeds of Ambrosia monogyra may likely be eaten by birds and small mammals.

Special Value to Native Bees, Butterflies and Insects
Ambrosia monogyra flowers may be visited by small butterflies, bees and other small insects.

The genus Ambrosia (Ambro'sia:) from Greek for "food of the gods." The genus Ambrosia was published by Carl Linnaeus in 1753.

The species epithet "monogyra" (monogy'ra:) in or with one circle, as in this species which has an inflorescence composed on one central whorl.

Seeds of Singlewhorl Burrobrush are used as a food source by Seris Indians, an indigenous group of the Mexican state of Sonora.
  • Seri Food, Unspecified, Seeds used for food; also used as a remedy for abdominal pains.

  • See complete species account from Native American Ethnobotany, University of Michigan, Dearborn.

    Date Profile Completed: 6/17/2013; updated 04/29/2020
    Arizona Flora, Kearney, Thomas H., Peebles, Robert H., 1960, University of California Press, Berkley and Los Angeles, as Hymenoclea monogyra.
    U.S. Dept. of Agriculture, Natural Resources Conservation Service on-line database and USGS ITIS search - (accessed 04/22/2020) for Ambrosia, includes Hymenoclea
    The Plant List (2013). Version 1.1. Published on the Internet; (accessed 04/22/2020).
    David J. Keil 2012, Ambrosia monogyra, in Jepson Flora Project (eds.) Jepson eFlora, /eflora/eflora_display.php?tid=80421, accessed on April 29, 2020.
    John L. Strother| Family List | FNA Vol. 19, 20 and 21 | Asteraceae | Ambrosia; 1. Ambrosia monogyra (Torrey & A. Gray) Strother & B. G. Baldwin, Madroño. 49: 143. 2002. Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 16+ vols. New York and Oxford.
    FNA 2006, Benson and Darrow 1981, Kearney and Peebles 1969; Editors; S.Buckley 2010, F.S.Coburn 2015, A.Hazelton 2015 from SEINet Field Guide, on-line; (accessed 04/06/2020).
    Wikipedia contributors. "Seri people." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 17 Mar. 2013. Web. 17 Jun. 2013.
    Wikipedia contributors, 'Ambrosia monogyra', Wikipedia, The Free Encyclopedia, 30 January 2018, 05:50 UTC, [accessed 29 April 2020]
    California Native Plant Society, Rare Plant Program. 2020. Inventory of Rare and Endangered Plants of California (online edition, v8-03 0.39). Website [accessed 29 April 2020].
    SEINet synonyms, scientific names, geographic locations, general information.
    Etymology: Michael L. Charters California Plant Names: Latin and Greek Meanings and Derivations; A Dictionary of Botanical and Biographical Etymology - (accessed 04/22/2020)