IPMP3.0, Oregon State University, Copyright 2000

Biology and Management of Prickly Lettuce


Registered Herbicides

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     Prickly Lettuce

 General Description:

  • Seedling leaves are slightly lobed with spines on underside of midrib.
  • Juvenile:  Low, prostrate to bushy rosette.  Leaves 2 to 10 inches long with lobed entire margins.  Blue green color, milky sap, and spiny midrib underside are identifying traits.
  • Mature:  Grows upright 1-5 feet tall with branches primarily in upper flowering portion of the plant.  Leaves are alternate, clasp the stem with angled lobes.  Roots, stems, and leaves exude a milky juice when broken.  Taproot.
  • Flower:  Flowers pale to bright yellow.  Flower ray 1/8-1/3 inch in diameter (may dry to a blue color).  Flowers borne on slender stalks, terminally at branch ends.

Life cycle: Winter annual or biennial

  • Reproduces only by seed.
  • May overwinter as a rosette.
  • Generally 1 stem arises from a rosette.
  • Flowers July-September.
  • May hybridize with cultivated lettuce.

Habitat/ Distribution:

  • Native to Europe but now naturalized throughout the U.S.
  • A weed in orchards, ornatmental stock, horticultural and agronomic crops, most irrigated crops, and roadsides.
  • Thrives on nutrient rich soils.

Herbicide Control Notes:

  • Gramoxone plus Goal effective. Stinger plus Buctril effective in spring when followed by Sinbar. Gramoxone plus Karmex/Direx or Gramoxone plus Sinbar effective in late fall.