Weed of the Week: Prickly Lettuce

Written by:  Garret Montgomery, Jason Bond, and Tom Eubank

Prickly Lettuce
Scientific Name:  Lactuca serriola L.
Family:  Asteraceae
Synonyms:  compass plant, lobed pickly lettuce, wild lettuce

Prickly lettuce is an erect winter annual or biennial broadleaf weed that can grow up to 6 feet tall.  Seedling leaves are oblong and form a low-growing rosette.  Leaves on older plants are deeply lobed, hairless, range from 2 to14 inches long, and are usually pale green in color.  They grow in an alternate, clasping pattern (no petioles) with prominent midveins.  Stem are hollow and filled with white, milky sap.  Prickly lettuce produces yellow flowers, and seeds are similar to those of dandelion (Taraxacum officinale).  As the name suggests, plants are mostly covered in spines along the leaf margins and on the underside of the leaf, down the midvein.  Prickly lettuce can be confused with annual sowthistle (Sonchrus oleraceus) or spiny sowthistle (Sonchrus asper).  Generally, prickly lettuce has more prominent spines than sowthistle species, and sowthistle species do not produce spines along the leaf midvein.

 Prickly lettuce is native to Europe but can be found throughout the contiguous United States with the exception of southern Florida. It can be found in disturbed areas, pastures, waste sites, railroad beds, agricultural fields, and fencerows.  In field crops, it is generally controlled with burndown herbicides targeting other winter annual weed species.  Glyphosate, dicamba, 2,4-D, or mixtures of these herbicides control prickly lettuce following applications made to plants less than 4 to 6 inches tall.  Although it is not toxic to animals, it can be problematic in pastures because the spiny leaf margins make it undesirable as livestock forage and it can reduce hay quality.

Bryson, C.T. and M.S. DeFelice. 2009. Weeds of the South. Athens, GA: University of Georgia Press. pp. 92.