Mowing will achieve control over time. Do it frequently enough that you remove the flower heads before they become seed pods.
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.
This pesky weed is small enough to hide among your landscape plants. Its extensive seed expulsion means that just one or two weeds can spread quickly through the garden in spring. Early control for hairy bittergrass is essential to protect the rest of the landscape from an infestation.
Cultural Control for Hairy Bittercress
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.
The weed prefers cool, moist soil and is most prolific after early spring rains. The weeds spread quickly but their appearance reduces as temperatures increase. The plant has a long, deep taproot, which makes pulling them out manually ineffective. Control for hairy bittercress is cultural and chemical.
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.
In turf, weeds like bittercress are a sure sign of poor lawn care. The answer is not to poison yourself and the environment (and kill your grass) in a futile attempt to remove the weed, but to care for your lawn correctly and deny the weed a place to live. Take good care of your grass and a harmless little plant like this should never have a chance to get established, much less thrive.
If you scalp the lawn, weeds will thrive. If you water it frequently for short periods of time, weeds will thrive. And if you feed the poor heat-stressed thing in summer, weeds will take over.
If I don’t get to them in time, I toast the seedheads with my trusty flame weeder before I pull the plants, just like I do with dandelions that have progressed to the puffball stage. Dandelion seeds burst into little flares of color—like Munchkin fireworks. Bittercress seeds explode with a loud ‘pop’. (Organic gardening is SO much more fun than spraying hormonal disruptor around!)
But I like to wait until after the little white flowers form to pull these weeds. Their flowers open up right before the blooms on my fruit trees, attracting lots of the pollinators and beneficial insects I’ll need to get a good fruit set and to fight all the pests that want to eat those peaches as much as we do.
For a Northern, cool-season lawn (one composed of cool-season grasses like rye, fescue and/or bluegrass) that means never cutting shorter than three inches, never feeding in summer, watering deeply but infrequently, and giving the lawn a big natural feeding in the Fall.
Its small white flowers are similar to those of chickweed, another ‘unwanted plant’ that blooms early in the Spring. But chickweed is more of a flat, spreading, mat-like plant. And its seedpods aren’t faster than a speeding bullet. Both weeds are remarkably easy to control in flowerbeds; just pull them, roots and all, out of wet soil. Chickweed comes out in big clumps, while bitter cress has a nice little stalk that gives you a handle to grab onto. Just remember to soak the soil first; all weeds come out of wet soil MUCH easier than dry.
If I’m paying attention and life cooperates, I’ll pull the weeds while they’re still in flower and before they set seed. Both weeds get composted—mixed into a good amount of shredded leaves hoarded from the previous fall; at least two parts leaves to every part green weed. The bitter cress typically comes up with a good amount of soil attached to its roots, which adds microbial life to the pile; and the chickweed has a lot of water content to help keep the moistness levels right.