Wild lettuce, China lettuce, or Compass plant.
Prickly Lettuce, Lactuca Serriola L., a native to the Mediterranean region is. The plant is sometimes called wild lettuce, China lettuce or compass plant because the leaves on the main stem are held vertically in a north-south plane, perpendicular to direct sunlight.
Prickly lettuce may be mistaken for dandelion, at the rosette stage, or for sow-thistles at any stage. All of these species are members of the sunflower family, contain a milky latex and produce numerous wind-dispersed seeds. Prickly lettuce is an annual weed growing from 1 to 5′ in height. Prickly lettuce has a deep tap root which will exude a milky sap. The leaves are alternate, clasp the stem, and are deeply lobed with spiny margins. The leaves have a row of spines along the mid-vein of the lower surface which is a distinguishing characteristic of this plant.
Prickly lettuce is drought tolerant and can have detrimental effects on crop value and harvesting efficiency of wheat. The flower buds can be difficult to screen out of grain, resulting in discounted prices. The sticky white latex in the stems can clog harvesting equipment and raise the moisture content of the grain.
Hand pulling: Hand pulling is effective for small infestations if it’s done when the ground is moist.
Biological: Sheep and goats enjoy feeding on prickly lettuce and will devour whole fields of this weed.
Chemical: Rosettes of prickly lettuce can be controlled in the fall or spring by non-selective herbicides containing glyphosate, glufosinate, or paraquat, however, populations of prickly lettuce are extremely tolerant of glyphosate herbicide. Plants are difficult to control with herbicides once the flowering stems have begun to elongate.
Preemergence applications of products containing atrazine, metribuzin, chlorsulfuron, isoxaben, oxyfluorfen, oxadiazon or terbacil will usually control germinating seedlings. Postemergence applications of 2,4-D, MCPA, dicamba, chlorsulfuron+metsulfuron, pyrosulfotole, bromoxynil, clopyralid, metribuzin, tribenuron or thifensulfuron-methyl/tribenuron-methyl, can control prickly lettuce rosettes in a variety of crops.