Shepherd's purse takes both its common name and its botanical name, Capsella bursa-pastoris, from the shape of the seed pods which resemble purses once carried by shepherds.
Shepherd's purse is a member of the mustard family. Its young leaves can be used as salad greens or steamed, and are said to taste a bit like cabbage. The powdered seeds have been used as a seasoning from ancient times through the present.
Seeds of this annual or winter annual frequently germinate in the fall and form a flat rosette of deeply-lobed leaves. In May, a flower stalk, which usually ranges in height from 6 to 18 inches, emerges from the center of the rosette. It produces tiny, white flowers with four petals, which mature into heart- shaped seed pods. The 1/4-inch long seed pods are divided into two parts and yield sticky seeds that remain viable in the soil a long time.
In flower and vegetable gardens, shepherd's purse can be controlled by hoeing or hand weeding the young plants. Trifluralin (Preen) or DCPA (Dacthal) may be used in gardens as a pre-emergence herbicide. Pre-emergence herbicides prevent many desirable seeds from sprouting, so use them only after desired plants are established, unless the label suggests otherwise. Be sure to read the label carefully to check whether the product is approved for use on the plants in YOUR garden.
In lawns, frequent mowing and improving soil fertility encourage vigorous, dense grass growth which helps prevent shepherd's purse from becoming established. However, shepherd's purse is one of a few weeds which can not be eliminated by frequent mowing, alone. Once the seeds have germinated, shepherd's purse will thrive at even the lowest mowing height, due to its flat rosette of foliage.
Shepherd's purse is more easily controlled using post-emergent herbicides. Unless weeds are scattered evenly throughout the lawn, spot spray them with a liquid herbicide rather than applying a weed and feed over the entire lawn. Buy a ready-to-use formulation or mix a small amount of concentrate with water.
If you'd rather not spray, you can wipe herbicide onto individual plants. Tie a sponge to a stick then dip the sponge into the diluted herbicide or use a small paint brush to treat each weed. Use a post-emergent herbicide labeled for turf that contains the following active ingredients:
- 2,4-D (2,4-Dichlorophenoxyacetic acid) and MCPP (2-(2-Methyl-4-chlorophenoxy) propionic acid)
- 2,4-D, MCPP and dicamba, a combination called Trimec which is sold under that name or is listed as an ingredient of other weed control products. Do not apply any product containing dicamba underneath the canopy of young trees, near shrubs or close to gardens as it can be absorbed by their roots.
Apply herbicide mid-spring and again in mid-autumn if a fall crop of shepherd's purse emerges. These herbicides are most effective when temperatures are between 60-80 degrees F. Do not spray if temperatures are projected to exceed 85 degrees within the next 48 hours. Choose a time when no rain is forecast for at least 24 and preferably 48 hours. To avoid herbicide drift, spray only when the air is still. Drift can harm or kill desirable broadleaf plants such as flowers, vegetables, trees and shrubs.