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Ambrosia acanthicarpa
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Annual Bursage
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Ambrosia acanthicarpa

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About Annual Bursage (Ambrosia acanthicarpa) Ambrosia acanthicarpa is a species of ragweed known by the common names flatspine burr ragweed, annual burrweed, and annual bur-sage. This spiny, weedy plant grows in clumps of many erect stems which may reach over a meter in height. Its gray-green stems are covered in a coat of stiff, bristly hairs. The few rough leaves are several centimeters long. The racemes of flowers are more plentiful, with each hairy flower head a few millimeters wide. The spiny, burr-like pistillate heads have pointed, twisting leafs and the staminate heads are rounded. This ragweed is native to western North America. It is adaptable and grows well in disturbed areas, easily becoming weedy.
Plant Description
Plant Type
Annual herb

Max. Height
3.3 - 5 ft (1 - 1.5 m)

Flower Color

Flowering Season
Summer, Fall

Native Status

Natural Setting
Site Type
Sandy plains

Sun, Part Shade

Elevation ?
-15' - 8086'

Annual Precip. ?
3.0" - 51.7"

Summer Precip. ?
0.12" - 2.58"

Coldest Month ?
25.8° F - 59.2° F

Hottest Month ?
53.6° F - 88.8° F

Humidity ?
0.65 vpd - 39.49 vpd


Landscaping Information
Ease of Care
Moderately Easy

Water Requirement ?
Very Low
Extremely Low
Very Low
Moderate - High

Nursery Availability
Rarely Available

Other Names
Common Names
Flatspine Burr Ragweed, Flatspine Bur Ragweed, Annual Burrweed, Annual Bur-sage

Sources include: Wikipedia. All text shown in the "About" section of these pages is available under the Creative Commons Attribution-ShareAlike License. Plant observation data provided by the participants of the California Consortia of Herbaria, Sunset information provided by Jepson Flora Project. Propogation from seed information provided by the Santa Barbara Botanical Garden from "Seed Propagation of Native California Plants" by Dara E. Emery. Sources of plant photos include CalPhotos, Wikimedia Commons, and independent plant photographers who have agreed to share their images with Calscape. Other general sources of information include Calflora, CNPS Manual of Vegetation Online, Jepson Flora Project, Las Pilitas, Theodore Payne, Tree of Life, The Xerces Society, and information provided by CNPS volunteer editors, with special thanks to Don Rideout. Climate data used in creation of plant range maps is from PRISM Climate Group, Oregon State University, using 30 year (1981-2010) annual "normals" at an 800 meter spatial resolution.

Links:   Jepson eFlora Taxon Page  CalPhotos  Wikipedia  Calflora

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