Lactuca serriola

Lactuca serriola, also called prickly lettuce, milk thistle (not to be confused with Silybum marianum, also called milk thistle), compass plant, and scarole, is an annual or biennial plant in the tribe Cichorieae within the family Asteraceae. It has a slightly fetid odor and is commonly considered a weed of orchards, roadsides and field crops. It is the closest wild relative of cultivated lettuce (Lactuca sativa L.).

Lactuca serriola is native to Eurasia and north Africa, and has become naturalized elsewhere.

Lactuca serriola has a spineless reddish stem, containing a milky latex, growing up to 2 metres (6 ft 7 in).

The leaves get progressively smaller as they reach its top. They are oblong or lanceolate, often pinnately lobed and (especially for the lower leaves), waxy grey green. Fine spines are present along the veins and leaf edges. The undersides have whitish veins. They emit latex when cut.

The flower heads are 1–1.5 cm (1⁄2–1⁄2 in) wide, pale yellow, often tinged purple, with 12–20 ray flowers but no disc flowers. The bracts are also often tinged purple. It flowers from July until September in the northern hemisphere. The achenes are grey, tipped with bristles. The pappus is white with equal length hairs.

Lactuca serriola is known as the compass plant because in the sun the upper leaves twist round to hold their margins upright, pointing roughly south or north from the stem.

Similar to Mycelis muralis but showing more than 5 florets.

Lactuca serriola is native to Europe, Asia, and north Africa, and has become naturalized elsewhere.