Lactuca scariola Linn. (Asteraceae), L.serriola Linn.
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 daisy family Asteraceae. It is slightly foetid, and is commonly considered a weed of orchards, roadsides and field crops. It is the closest wild relative of cultivated lettuce (Lactuca sativa L.). It is known as the compass plant because in the Sun the upper leaves twist round to hold their margins upright. It is native to Europe, Asia, and north Africa, and has become naturalized elsewhere.
It has a spineless reddish stem, containing a milky latex, growing from 30 to 200 cm. The leaves get progressively smaller as they reach its top. They are oblong lanceolate, often pinnate 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 11 to 13mm wide, are pale yellow, often tinged purple. The bracts are also often tinged purple. It flowers from July until September. The achenes are grey, tipped with bristles. The pappus is white with equal length hairs.