Triangle-leaf Bursage
Ambrosia deltoidea
(Franseria deltoidea)
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 
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.
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.
UNARMED.
PAPPUS: Absent.
Asteraceae -- Sunflower Family
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