Virginia Tech Weed Identification Guide

Prickly Lettuce: Lactuca serriola

plettuce2-23.jpg (220887 bytes) Identifying Characteristics: An annual or biennial weed with prickly leaves that emit a milky sap when cut.  Prickly lettuce is most commonly a weed of nurseries, orchards, roadsides, and agronomic crops and is found throughout the United States.
Seedlings:  Cotyledons are oval.   Young leaves are also oval with spiny leaf margins and spines along the midvein of the lower leaf surface. plettuce11-27.jpg (107453 bytes)
Leaves:   Arranged alternately along the stem, ranging from 2 to 14 inches long.  Most leaves are distinctly lobed and have leaf bases that clasp the stem.  All leaves have prickles that occur along the leaf margins and along the midvein on the lower leaf surfaces.  Leaves emit a milky sap when cut and become progressively smaller up the flowering stem.
 

Stems:  Erect, hollow, light green to white, reaching 5 feet in height.  One stem emerges from the central rosette and this stem then branches in the upper portions of the plant.  Stems emit a milky sap when cut.

Roots: A taproot.

Fruit:  An achene containing a single seed.

plettuce10-14b.jpg (87071 bytes)
Flowers: Many flowers are produced in the upper portions of the plant that branches outwards and resembles a cone.   Individual flowers are approximately 10 mm wide and are composed of 5 to 12 yellow toothed petals.
Identifying Characteristics:  This weed has leaves with prickles along the margins and on the midveins of the lower leaf surfaces.  Additionally, all parts of the plants emit a milky sap when cut.  All of these characteristics help to distinguish prickly lettuce from similar species, such as Annual Sowthistle (Sonchus oleraceus) and other sowthistles. plettuce9-24.jpg (62374 bytes)