White Bursage

Ambrosia dumosa
(Franseria dumosa)

Ambrosia dumosa Pen & Ink illustration © by Michael Plagens

Illustrated from live specimen found at KOFA Mountains, Yuma Co., Arizona. 14 March 1993.

LEAVES: Leaves are pinnately divided into almost linear segments and are whitish. Foliage releases pungent sage-tarragon aroma on being crushed.

FLOWERS: These are composite flowers with male and female flowers in separate heads on the same plant. The terminal spikes have several heads of only female flowers below and a larger number of exclusively male-flowered heads above. The petals are vestigial yet the male flowers appear yellow because of the copious pollen. Anemophilous pollination means that during the spring blooming period allergy patients will suffer and most everyone else will at least notice the abundant grit in the eyes.

ACHENE: The one or two achenes of the female flower heads are enclosed in spine-hooked bracts. These mature into burrs that affect dispersal.

SHRUB: A small- to medium-sized shrub normally less than ½ m tall.

RANGE: Common on the flats at lowerer elevations (usu. less than 350 m) in the Sonoran Desert than Triangle-leaf Bursage, Ambrosia deltoidea.


PAPPUS: Absent.

Burs of White Bursage, Ambrosia dumosa, photo © by Michael Plagens

Foothills of the Harquahala Mountains, western Maricopa Co., Arizona. May 2020.

Asteraceae -- Sunflower Family

More Information:

Sonoran Desert Field Guide
Sonoran Desert Places
Sonoran Desert Naturalist Home Page


Copyright Michael J. Plagens, page created 10 May 2004,
updated 26 May 2020.