Hairy Bittercress Killer: Learn More About Control For Hairy Bittercress


By: Bonnie L. Grant, Certified Urban Agriculturist

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.

What is 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.

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.

Preventing Hairy Bittercress in the Garden

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.

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.

Cultural Control for Hairy Bittercress

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.

Mowing will achieve control over time. Do it frequently enough that you remove the flower heads before they become seed pods.

As temperatures get warmer, the plant will die naturally without having reproduced. That means fewer weeds the following season.

Chemical Hairy Bittercress Killer

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.

The higher number preparations will kill a wide range of weeds. The two-way herbicide should be sufficient for your purposes unless you have a field full of a variety of weed pests as well as the hairy bittercress weed. Apply your chosen herbicide in spring or fall.

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Hairy Bittercress Weed - What Is Hairy Bittercress And How To Control It - garden

Like many common garden weeds, hairy bittercress (Cardamine hirsuta) is a tiny, tender annual that you probably don’t notice growing all around you – until you start looking for it.

Sometimes referred to as “garden cress,” “pepper cress,” or “popweed,” this unassuming bitter herb is a member of the Brassicaceae plant family, placing it in the esteemed company of mustards, cabbages, broccoli and the like. That means it’s not only edible, but a delight to the senses as well.

Information on this cool-weather mustard is somewhat sparse, and so I can’t say for sure what its nutritional profile looks like. I would suspect that it’s similar to other Brassicas, but perhaps more concentrated due to its compact size. You could bet on a healthy dose of vitamin C and some essential minerals, no doubt.

If you’ve ever eaten microgreens before, your palette will already be familiar with what you get from hairy bittercress: soft, tender leaves and a sharp, peppery flavor that makes it an excellent garnish or addition to a salad mix.

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Hairy Bittercress Facts

  • Seeds from Hairy Bittercress germinate when the soil temperature is cool
  • Research suggests that the seeds will not germinate in high temperatures. It is almost that the plant requires a ‘summer’ stratification.
  • Native to Europe and Asia, it has become established all over the world
  • Seed capsules will ‘explode’ when ripe, throwing the seed up in the immediate area
  • The plant goes dormant once the temperatures warm up, and you will not see it again until Fall
  • The Scientific Name of Hairy Bittercress is Cardamine hirsuta
  • Hairy Bittercress is a member of the mustard family

Hairy bittercress is a winter annual weed. The seeds germinate from late summer through the fall, then overwinter and continue to grow in early spring. http://extension.umd.edu/hgic/hairy-bittercress

You can hand-pull or mow bittercress to remove the seedheads before the plants mature, to prevent the spread of the seeds. Bag the clippings and put them in the trash (not compost).

Another option is to spot-treat the weed with a broadleaf postemergent herbicide when the weeds are actively growing in the spring. If you need a postemergent herbicide, look for one that lists hairy bittercress on the label and follow the label instructions.

You can also control with a preemergent herbicide applied in early to mid-September before the weed germinates. However, if this is in your lawn, for example, you would not be able to sow grass seed in the fall, as the preemergent would inhibit its growth.


MSU Extension Gardening in Michigan

Updated from an original article written by Diane Brown.

Hairy bittercress is an annual weed that can spread quickly.

Flowers and seed pods of hairy bittercress. Photo by Lori Imboden, MSU Extension.

Have you recently noticed plants with small, white flowers on the edges of your lawn, flowerbeds and rock pathways? During April and May, populations of the winter annual weed hairy bittercress (Cardamine hirsuta) becomes increasingly visible. Hairy bittercress has a low growing rosette similar in form to a dandelion. It raises its profile in early spring with the appearance of flowers and seeds on a vertical stem. Like many members of the mustard family, hairy bittercress sets seed prolifically. It grows quickly and a few plants or seeds can generate a more widespread infestation in even a year’s time.

The first true leaves of hairy bittercress are heart shaped. Photo by Erin Hill, MSU.

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 can propel the seeds as far as 16 feet from the mother plant. This seed dispersal adds to the soil seed bank and primes the area for another infestation to emerge in early fall. After setting seed, the life cycle is complete and the plants die. Hairy bittercress and other winter annual weed species, like common chickweed and purple deadnettle, are not typically present during the summer months.

Hairy bittercress leaves have two or more pairs of leaflets and a kidney shaped terminal leaflet. Photo by Lori Imboden, MSU Extension.

Once the seed pods ripen, disturbing the pods can propel the seeds as far as 16 feet from the mother plant. This seed dispersal adds to the soil seed bank and primes the area for another infestation to emerge in early fall. After setting seed, the life cycle is complete and the plants die. Hairy bittercress and other winter annual weed species, like common chickweed and purple deadnettle, are not typically present during the summer months.

Once the seed pods ripen, disturbing the pods will send the seeds flying as far as 16 feet. 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.

If plants have already emerged, applying a post-emergence herbicide to actively growing plants before seedpods form may be effective. If using an herbicide, be certain it contains an active ingredient that will target this weed. Always read and follow all labeled instructions to increase effectiveness and prevent personal or environmental harm.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).

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Cardamine hirsuta(hairy bittercress). Photo by Saara Nafici.

Cardamine hirsuta's toothpick-like seed capsules coil up tightly and then explode when touched, flinging the seeds far from the mother plant. Photo by Saara Nafici.

" > Show larger version of the image Hairy Bittercress Cardamine hirsuta's toothpick-like seed capsules coil up tightly and then explode when touched, flinging the seeds far from the mother plant. Photo by Saara Nafici. Hairy Bittercress

Cardamine hirsuta (hairy bittercress) is shallow-rooted fairly easy to pull by hand. Photo by Saara Nafici.

" > Show larger version of the image Hairy Bittercress Cardamine hirsuta (hairy bittercress) is shallow-rooted fairly easy to pull by hand. Photo by Saara Nafici.

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Fauna

Although Hairy Bittercress is invasive, it does add a small benefit to wildlife. Butterflys do visit/pollinate the flowers in the Spring. Particularly the Sping Azure butterfly.

Read more about other invasive plants, and how to control them by clicking on our link below!

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