Prickly Lettuce
Lactuca serriola
Photographed along Mesquite Wash, Maricopa Co., Arizona. Aug. 1, 2009.
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ANNUAL: A common to abundant weed of disturbed soils at roadsides, in
gardens, and along washes. Grows upright with few branches below. Plants
growing to nearly 2 m tall are not
uncommon.
RANGE: A cosmopolitan weed native to Eurasia and now found throughout
North America. In the Sonoran Desert it is found in urban areas, agricultural
margins and along riparian streams.
LEAVES: Margins of the leaves have sharp teeth and indentations. The
teeth have prickles at the tip of each dentition. Milky sap from broken stems.
More leaves are at base of plant and smaller leaves scattered up stems.
Leaf of Prickly Lettuce seen near Pinetop, Arizona, Aug. 2009.
FLOWERS: Small, pale yellow, flower heads composed entirely of yellow
strap-shaped florets flared out pin-wheel fashion. The florets open early
morning in the desert and close before temperatures get too hot. The
inflorescence stems are stiff and wirey and widely branched into a panicle.
Flowering here late spring though fall.
FRUIT: The achene seeds bear a
pappus of many fine capilary bristles at the top and have a beak at
the top.
ARMED: The prickles can be surprisingly sharp.