Shepherd's-purse is a winter annual. It forms basal leaves as well as alternating stem leaves. The basal leaves are deeply lobed, pointing away from the base. The root of shepherd's-purse is a slender taproot, combined with secondary fibrous roots.
Shepherd's purse does not compete with an actively growing turf stand. It will develop in areas that have been damaged over the summer and have not filled in during the fall. Fall seedlings that have not completely developed are susceptible to shepherd's purse invasion over the winter. The plant dies quickly after producing its seedhead in the spring. Proper mowing will reduce seed production, as the seedhead is erect.
Source: Virginia Polytechnic Institute & State University