Mowing will achieve control over time. Do it frequently enough that you remove the flower heads before they become seed pods.
Hairy bittercress weed (Cardamine hirsuta) is an annual spring or winter pest. The plant springs from a basal rosette and bears 3 to 9 inch (8-23 cm.) long stems. The leaves are alternate and slightly scalloped with the largest at the base of the plant. Tiny white flowers develop at the ends of the stems and then turn into long seedpods. These pods split open explosively when ripe and fling seeds out into the environment.
As temperatures get warmer, the plant will die naturally without having reproduced. That means fewer weeds the following season.
Cultural Control for Hairy Bittercress
Severe infestations of hairy bittercress weed will require chemical treatment. Herbicides applied post emergence need to have two different active ingredients. The ingredients must be 2-4 D, triclopyr, clopyralid, dicamba, or MCPP. These are found in broadleaf herbicide preparations known as two, three, or four-way treatments.
Prevent invasions into turf areas by encouraging good grass growth. The weeds easily infest thin or patchy areas. Apply several inches (8 cm.) of mulch around landscape plants to help prevent seeds from getting a foothold in your soil.
Pulling out hairy bittercress weed usually leaves the root behind. The plant will re-sprout from healthy weeds and the problem persists. You can, however, use a long slim weeding tool to dig down and around the taproot and get all the plant material out of the ground.
Late winter and spring signal growth of all plants, but especially weeds. Annual weed seeds overwinter and then burst into growth towards the end of the season. Hairy bittercress weed is no exception. What is hairy bittercress? The plant is an annual weed, which is one of the earliest to sprout and form seeds. Control for hairy bittercress starts early in the season, before flowers turn to seed and get a chance to spread.
Flowers and seed pods of hairy bittercress. Photo by Lori Imboden, MSU Extension.
Hairy bittercress is best managed mechanically when it is young. Remove it by hand, hoe or tillage in early fall or early spring before it sets seed. If plants are flowering, composting is discouraged as seeds may develop. To manage this weed using herbicides, the proactive approach would be to use a pre-emergence herbicide in the late summer (late August to early September) to target the plants at the time of germination and prevent successful emergence.
Hairy bittercress is an annual weed that can spread quickly.
Hairy bittercress is a winter annual weed. Its seeds germinate in fall beginning as early as September. The first true leaves are heart-shaped, followed by compound leaves with two or more pairs of leaflets and a kidney shaped terminal leaflet. The leaves that emerge in the fall form a small rosette that will overwinter. Once the weather warms in spring, it sends up stalks of small, white flowers followed by slender seed pods known as siliques.
Once the seed pods ripen, disturbing the pods will send the seeds flying as far as 16 feet. Photo by Lori Imboden, MSU Extension.