Spiny sowthistle is a winter annual that is actually in the sunflower family and not a true thistle. The leaves form basal and are deeply lobed. They then alternate on stems. The upper leaves are less lobed but have spiny edges. The stems are hollow and contain hair on only the lower portion. Both the leaves and stems contain a milky solution. The stems only branch in the inflorescence. Spiny sowthistle spreads by seed. It flowers from late spring through the summer, depending on the location. The flower is yellow, resembling a dandelion, but forms in a corymbiform cluster. The root of spiny sowthistle is a taproot. Spiny sowthistle is found throughout the United States.
Spiny sowthistle is found in waste areas and other open areas such as roadsides and thin turf. It can be controlled by mowing which prevents the stem and flowers from forming and eliminates seed formation. The plant can also be cut out.
Make your post-emergence herbicide application when spiny sowthistle is young and actively growing. For best results, treat prior to bolting.