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Ministry of Agriculture, Food and Rural Affairs

Prickly Lettuce

Scientific Name: Lactuca scariola L.

Other Names: LACSE, laitue scariole, Compass plant, Wild lettuce, laitue vireuse, scariole, Lactuca serriole L.

Family: Composite or Aster Family (Compositae)

General Description: Winter annual, biennial, or sometimes annual, reproducing only by seed. The whole plant has a milky white juice.

Habitat: Prickly lettuce occurs throughout Ontario in waste places, pastures, roadsides, cultivated fields, and occasionally in gardens.

Seedlings

Stem

  • Erect
  • 30- 150 cm (1- 5 ft.) high
  • Whitish-green
  • Usually smooth with a few prickles on the lower part
  • Rather finely branched at the top

Leaves

  • Variable in size and shape
  • Usually deeply lobed or nearly divided with backward curving lobes but sometimes with irregularly shaped lobes or without lobes
  • The outer (convex) margin of each lobe usually weakly spiny-toothed
  • The inner (concave) margin usually without teeth or with much smaller teeth
  • Leaves clasping the stem with basal lobes
    Underside of the midrib nearly always with a single row of stiff, sharp prickles, these usually absent from the upper leaves among the inflorescence and occasionally absent from the lower leaves of second growth after mowing
  • Leaves alternate
  • Usually twisted near the stem so the leaf blade is oriented with the margins pointing vertically and the flat surfaces facing horizontally
  • Leaf tips often (but not always) pointing north and south

Flowers

  • Heads small and very numerous on fine stalks in much-branched inflorescences
  • Each head about 7- 8 mm (1/4- 1/3 in.) long and about 3 mm (1/8 in.) across, with 5 to 12 yellow ray florets, the yellow colour often fading to bluish on drying
  • Disk florets absent
  • Seeds:
    • Narrowly oval
    • A long beak tipped with a tuft of white hair (pappus)
  • Flowers from June to late autumn

Often Confused With
Dandelion (Prickly lettuce is distinguished by the single row of firm, sharp prickles along the underside of the midribs of the stem leaves.)

Prickly lettuce seedling Prickly lettuce leaves Prickly lettuce leaves Prickly lettuce leaves Prickly lettuce flower
Click to enlarge.