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Triangle-leaf Bursage

Ambrosia deltoidea
(Franseria deltoidea)

Triangle-leaf Bursage, Ambrosia deltoidea, Pen & Ink by Michael Plagens

Illustrated from live specimen found at South Mountain, Phoenix, Maricopa Co., Arizona. 08 March 1993. a) involucre (head) of one to three pistillate (female) flowers, b) involucre of 20 - 30 staminate (male) flowers, c) a tephritid fruit fly, Eurestoides sp. that feeds as a larva within the developing seeds.

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FLOWERS: These are composite flowers with male and female flowers in separate heads on the odd looking flowers if you take the effort to examine closely 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 sufferer 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.
for most of year a non-discript shrub with ashy-geen appearance
LEAVES: Diamond to triangle shape. Texture is somewhat leathery. Leaves are readily shed with drought or after a hard freeze.

SHRUB: A medium-sized shrub normally about ½ m tall. Where this shrub is abundant a large portion of the shrubs will all be about the same size and evenly dispersed across the landscape.

RANGE: Very common to abundant on bajadas and flats in the Arizona Sonoran Desert mostly above 500 m elevation. At hotter, lower elevations it is replaced by Ambrosia dumosa , White Bursage.


PAPPUS: Absent.

Asteraceae -- Sunflower Family

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More Information:

Unopened flower buds of Ambrosia deltoidea

Sonoran Desert Field Guide

Sonoran Desert Places

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Copyright Michael J. Plagens, 1999-2011