Skeleton Weed
Flatcrown Buckwheat
Eriogonum deflexum
Photographed at White Tank Mountains, Maricopa Co., Arizona. Aug 2009.
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LEAVES: Roundish to kidney-shaped leaves are all arranged at the base of
the plant while the highly branched stems above are green and photosynthetic.
ANNUAL: In the Sonoran Desert this is a common weedy plant along washes,
at roadsides, and on sandy, disturbed soil. Before the tall, branched flower
stalk forms the plant is very low growing.
FLOWERS: An intricately branched inflorescence forms the bulk of the
plant once blooming initiates. Hundreds of small clusters of even smaller
whitish flowers are disposed at the tips of the many branches. Blooming from
late spring through fall, moisture permitting.
FRUIT: Small, single seeded fruits are three-sided like other
buckwheats.
RANGE: Common in the Sonoran Desert in Arizona and Mexico in washes and
along roadsides. Also ranges into low elevations of the Mojave and Chihuahuan
Deserts.
UNARMED
The structure of this plant demonstrates two very different xerophytic adaptations. First the broad leaves are set very close to the soil. Here, next to the ground, there is a boundary layer of slower moving, slightly more humid air. In this microenvironment the leaves can better perform their photosynthetic work while minimizing water loss. Surprisingly, there is competition for pollinators at critical times and as a result tall flowering stems that can push above the competition have been selected for. Making double-use of this scaffolding for photosynthesis, skeleton weed inflorescence stems are smooth, green and leaf-free. Thus above the soil boundary layer, where drying winds are persistent, skeleton weed minimizes water loss by minimizing leaf surface area while keeping overall surface area high to improve heat dissipation and thus increase photosynthetic efficiency.