Typical plant growing in a disturbed site

Typical plant growing in disturbed site. Photo by S. Donaldson.

close up photo of seedling stems

Note the hairs on the seedling stems. Photo by W. Hanson Maze
 

Photo of grayish green colored leaves

The leaves lobed and grayish green in color. Photo by S. Donaldson
 

Photo of flowers in clusters at the end of a stem

The flowers occur in clusters at the end of stems. Photo by S. Donaldson.
 

 

Other common names

Flatspine bur ragweed, sand-bur, annual burweed

Scientific name

Ambrosia acanthicarpa

Family

Asteraceae

Description

Annual bursage grows to 3 feet tall and is common in disturbed sites as well as in various plant communities.

  • Leaves

    Grayish-green and lobed; covered with short, bristly hairs; oppositely attached to the stem toward the bottom of the plant, and alternately attached above.

  • Stems

    Gray-green and bristly.

  • Flowers

    Produces greenish male and female flowers on the same plant during the summer. Male flowers occur at the ends of branches. Female flowers are spiny and are found in the leaf axils

  • Roots

    Grows a slender taproot and many fibrous roots.

Native to

North America

Where it grows

Roadsides, vacant lots, pastures, agricultural fields and disturbed areas, dry and moist sandy soils

Life cycle

Annual (lives one year)

Reproduction

Reproduces by seed; burs stick to surfaces, helping spread this weed

Control methods

Little information is available on the control of annual bursage. As with all annuals, preventing seed production is essential. Control before seedheads are produced.

 

  • Mechanical

    Cultivation helps to control this plant. Dig, hoe or pull young plants. Plants may regrow if mowed.

    Cultural

    Plant desirable vegetation to help suppress it.

    Biological

    None commercially available.

    Chemical

    Try broadleaf-selective herbicides such as 2,4-D + dicamba on young plants. Dicamba can persist for several months and may damage desirable plants in the area treated. Glyphosate can also be used on young plants but is nonselective and damages both grasses and broadleaf plants. Pre-emergence herbicides can be used to manage existing seed banks.

References

CA Dept. of Food and Agriculture. 2011. Annual bursage, http://www.cdfa.ca.gov/phpps/ipc/ weedinfo/ambrosia.htm.

DiTomaso, J.M. and E.A. Healy. 2007. Weeds of California and Other Western States. University of California Publication 3488.

UC Berkeley Jepson Manual. 2011. Ambrosia acanthicarpa Hook, http://ucjeps.berkeley.edu/ cgi-bin/get_JM_treatment.pl? Ambrosia+acanthicarpa.

USDA-NRCS Plants Database. 2011. PLANTS profile for Ambrosia acanthicarpa, http://plants.usda.gov/java/nameSearch.

Whitson, Tom D. (editor). 2002. Weeds of the West. University of Wyoming, Jackson, Wyoming.

Donaldson, S. and Hanson Mazet, W. 2011, A Northern Nevada Homeowner’s Guide to Identifying and Managing Annual Bursage, Extension | University of Nevada, Reno, FS-11-64
Printable    Version    (PDF)

Extension Associated Contacts

Wendy Hanson Mazet
Wendy Hanson Mazet
 

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