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Flatspine bur ragweed

Ambrosia acanthicarpa

Also called Sandbur, Flatspine burr ragweed, Annual bursage, Hooker's Bur Ragweed, Flat Spine Burr Ragweed, Annual Bur Sage, Burr Ragweed

Flatspine bur ragweed
Photo: Anthony Valois and the National Park Service, Public domain

Flatspine bur ragweed is a bristly annual weed in the daisy family, native to western North America and common in disturbed ground. It grows readily in poor, open sites where little else thrives.

Family
Asteraceae (Daisy family)
Grows as
Annual
Light
Full sun
Water
Water sparingly; it tolerates dry conditions once established.
Soil
Poor, sandy or disturbed soil; it does not need rich soil.
Temperature
Hardy in temperate climates; grows through warm summers and tolerates cold winters as seed.
How easy
Easy
Native range
W. & C. Canada to N. Mexico
Climate
temperate

About

Ambrosia acanthicarpa is a North American species of bristly annual plants in the family Asteraceae. Members of the genus Ambrosia are called ragweeds. The species has common names including flatspine bur ragweed, Hooker's bur-ragweed, annual burrweed, annual bur-sage, and western sand-bur. The plant is common across much of the western United States and in the Prairie Provinces of Canada.

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 bracts and the staminate heads are rounded. The species is adaptable and grows well in disturbed areas, easily becoming weedy.

Other Ambrosia plants

Ambrosia leaf bur ragweed · Ambrosia arborescens · Annual ragweed · Lanceleaf ragweed · Silver bur ragweed · Rio Grande ragweed · San Diego bur ragweed · Weakleaf bur ragweed · Tucson bur ragweed · Triangle bur ragweed · Burrobush · Woolly fruit bur ragweed

Text excerpted from the Wikipedia article Ambrosia acanthicarpa by its contributors, under CC BY-SA 4.0; the excerpts and the care summary drawn from them are shared under the same licence.

The care summary was written by AI (Claude, Anthropic) from the sources on this page, with general growing knowledge where they are silent. Check before relying on it.

Life form, climate and native range: World Checklist of Vascular Plants, Royal Botanic Gardens, Kew (CC BY 3.0), reformatted; see Plants of the World Online.

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