prickly lettuce

Lactuca serriola L.

Description from Invasive.org

Appearance
Lactuca serriola is an annual or biennial that can reach heights of 6 ft. (1.8 m).
Foliage
Cauline leaves (on the stem) are alternate, 2-14 in. (5-36 cm) long and become smaller up the stem. Leaves have a conspicuous, white midvein with the underside of the vein covered with many prickles.
Flowers
In the mid-to-late summer, 0.5 in. (1.3 cm) wide, yellow flowers develop in a branched inflorescence at the apex of the stem.
Fruit
Flowers produce dandelion-like seeds.
Ecological Threat
Lactuca serriola is native to the Mediterranean region and occurs along roadsides, in abandoned fields, and other disturbed areas. It was accidentally introduced into North America in the late 1890s, possibly as a contaminant in seed.

Selected Images from Invasive.org

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Plant(s)
Mary Ellen (Mel) Harte, , Bugwood.org
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Foliage Rosette
Steve Dewey, Utah State University, Bugwood.org
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Plant(s) habit
Forest and Kim Starr, Starr Environmental, Bugwood.org
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Plant(s) habit
Forest and Kim Starr, Starr Environmental, Bugwood.org
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Foliage
Mary Ellen (Mel) Harte, , Bugwood.org
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Feature(s) Milky sap
Tom Heutte, USDA Forest Service, Bugwood.org
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Flower(s)
Mary Ellen (Mel) Harte, , Bugwood.org
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Flower(s)
Mary Ellen (Mel) Harte, , Bugwood.org
Additional Resolutions & Image Usage
Fruit(s)
Steve Dewey, Utah State University, Bugwood.org
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Fruit(s)
Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org
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Feature(s) Prickles
Steve Dewey, Utah State University, Bugwood.org
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Infestation
Steve Dewey, Utah State University, Bugwood.org
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Plant(s) USDA NRCS. Wetland flora: Field office illustrated guide to plant species. USDA Natural Resources Conservation Service.
USDA NRCS PLANTS Database , USDA NRCS PLANTS Database, Bugwood.org
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Distribution