Prickly lettuce, also called wild lettuce or compass plant, is a winter annual. The leaves form in a basal rosette. Prickly lettuce has a deep tap root which will exude a milky sap. Prickly lettuce will produce an upright stem on which the leaves will be alternate. The mature leaves are deeply lobed. The leaves will twist vertical to the stem. The leaves have a row of spines along the mid-vein of the lower surface.
Compass plant or prickly lettuce is usually found in disturbed sites. It does best in thin low-maintenance turf. It produces an erect stem that will be removed by mowing. It prefers soils that are irrigated and higher in nutrients. It can be a problem in container grown ornamentals and be introduces into landscape beds and turf areas.
Source: Virginia Polytechnic Institute & State University