Typical plant growing in disturbed site. Photo by S. Donaldson.
Flatspine bur ragweed, sand-bur, annual burweed
Annual bursage grows to 3 feet tall and is common in disturbed sites as well as in various plant communities.
Grayish-green and lobed; covered with short, bristly hairs; oppositely attached to the stem toward the bottom of the plant, and alternately attached above.
Gray-green and bristly.
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
Grows a slender taproot and many fibrous roots.
Roadsides, vacant lots, pastures, agricultural fields and disturbed areas, dry and moist sandy soils
Annual (lives one year)
Reproduces by seed; burs stick to surfaces, helping spread this weed
Little information is available on the control of annual bursage. As with all annuals, preventing seed production is essential. Control before seedheads are produced.
Cultivation helps to control this plant. Dig, hoe or pull young plants. Plants may regrow if mowed.
Plant desirable vegetation to help suppress it.
None commercially available.
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.
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.
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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
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