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.
Typical plant growing in a disturbed site. Photo by S. Donaldson.
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.
The leaves are lobed and grayish-green in color. Photo by S. Donaldson.
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.
The flowers occur in clusters at the ends of stems. Photo by A. Brousseau, CDFA.
Roots
Grows a slender taproot and many fibrous roots.
Note the hairs on the seedling stems. Photo by W. Hanson Mazet.
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, CDFA.
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, UC/JEPS.
USDA-NRCS Plants Database. 2011. PLANTS profile for Ambrosia acanthicarpa, USDA.
Whitson, Tom D. (editor). 2002. Weeds of the West. University of Wyoming, Jackson, Wyoming.
