Herbicides That Kill Shepherd's Purse

Shepherd's purse (Capsella bursa-pastoris) is an annual broadleaf weed that invades yards and flowerbeds. Because shepherd's purse grows in a wide range of soils and in areas that receive sunlight to shade, gardeners find this weed all over their landscape. It is important to kill shepherd's purse using herbicides that will not harm turf grass or ornamental plants. When left untreated, shepherd's purse competes with desired vegetation for the soil's nutrients and moisture.

Pre-Emergent Herbicide

Pre-emergent herbicides prevent shepherd's purse seeds from germinating and sprouting plants in the early spring. One shepherd's purse plant can produce up to 33,000 seeds. Therefore, it is imperative that gardeners apply pre-emergent herbicides to prevent these seeds from germinating. Apply a pre-emergent herbicide in the early spring after the ground thaws. Spread a pre-emergent herbicide granule type that contains trifluralin on the lawn and ornamental flowerbed area using a drop spreader. Water the landscape to help the herbicide sink into the soil.

Post-Emergent Herbicide in Lawns

Shepherd's purse sprouts twice a year in the spring and fall. Gardeners must look out for the weed to apply post-emergent herbicides. One way to spot shepherd's purse in the landscape is to look for plants sprouting growth that resembles purses. These "purses" are called silicles and contain seeds. Spray weeds growing within the lawn with post-emergent herbicides that contain active ingredients, such as 2,4-D, MCPP or dicamba. Apply the post-emergent herbicides when air temperatures are between 60 and 80 degrees Fahrenheit.

Broad Spectrum Herbicide

Gardeners must kill shepherd's purse plants growing within ornamental flowerbeds with a broad spectrum herbicide. Because shepherd's purse weeds are broadleaf plants, there is no selective post-emergent herbicide option for use within broadleaf ornamentals. Use a broad spectrum herbicide that contains glyphosate. To use next to ornamental plants, cut a two-liter bottle in half. Place the half with the opening over the shepherd's purse. Spray herbicide through the opening. Reapply the spray in 10 days if the shepherd's purse hasn't died out.

Organic

Gardeners may use a vinegar herbicide on shepherd's purse plants. Vinegar kills these plants by drying them out or dehydrating them. The best way to spray vinegar on shepherd's purse plants is to wait for a dry warm day. Apply the vinegar to the leaves of the plant. Because vinegar may not be as caustic as other types of herbicides, gardeners may have to reapply throughout the growing season.

References

• Colorado State University Extension: Shepherd's Purse -- Capsella bursa-pastoris
• Colorado State University Extension; Green Gardening: Alternatives to Commercial Insecticides and Herbicides; Kathi Taylor
• Kingdom Plantae: Capsella Bursa-Pastoris
• University of California, Davis, Integrated Pest Program: Weed Control Using Herbicides
• University of California, Davis, Integrated Pest Management: Shepherd's-purse
• North Carolina State University: Weed Management in Annual Color Beds