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lawn weed that shoots seeds when touched

Call it what you will – hairy bittercress, winter bittercress, hairy cress, popping cress – Cardamine hirsuta – is a weed that tries the most forgiving gardener’s patience. Growing worldwide (except in the Antarctic, this genus of the Brassicaceae family numbers more than 150 species, both annual and perennial. The plant is self-pollinating and in bloom throughout the year. It loves moist soil and grows aggressively under those conditions.

As the snow melts, tiny white, pink, or lavender flowers begin to appear. Yes, flowers. This tenacious weed is short-lived, which is good, you say. A life cycle of 6 weeks doesn’t seem like such a big deal. Think again – how many 6-week cycles are there in a year?

One of the biggest problems with bittercress is that, by the time you discover you have a problem, it’s almost too late to do anything about it. The first flowers appear in late February or early March, quickly form seed pods, and mature. If you touch those trigger-happy seed pods, i t’s all over – the pods explode, distributing seeds over an area up to 36 inches around each plant. Those seeds will germinate and begin sprouting with a few days and the cycle begins again, only over a larger area. Small to medium size plants produce about 600 seeds, and larger plants can yield up to 1,000 seeds.

Hairy bittercress is not invasive enough to warrant using herbicides. As soon as new plants appear in February or March, begin pulling them; these are the offspring of the previous fall’s seed crop. Through the season, always pull the seedlings when you see them; they have shallow roots and come away quite easily; however, bits of root left behind are capable of re-rooting under optimum conditions. The key is to get the plants before they set seed, which happens quickly after blooming. Eradicating this weed from large areas is almost impossible, unless you can hoe and remove. Keeping bittercress out of the flower beds is a little easier, but requires diligent hand-weeding to stay ahead of the seed formation. The leaves release a pungent aroma when bruised.

(This article was originally published on March 29, 2010. Your comments are welcome but please be aware that authors of previously published articles may not be able to respond to your questions or comments.)

Spring is in the air, little green things are popping up all over, and we all heave a sigh of relief that the blanket of white stuff is finally gone. But beneath the snow that stopped everything in its tracks lurks a hardy, robust little puff of tiny green leaves that virtually grows before your eyes.

Hairy bittercress is a problem in greenhouses and nurseries, so be sure to clear off the top 2 to 3 inches of soil before planting anything you purchase. Scoop the soil into a plastic bag and dis card. Keep a close watch on newly planted containers, especially those that are positioned near flower beds. The propulsion factor of bittercress seeds can sneak new plants into your containers while you aren’t looking. Hairy bittercress is a real problem near flagstone patios or walks, brick work, or any hard-scaping that has space between the pieces. This weed does not need much to set down roots – even a small amount of sand between two bricks is plenty.

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.

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

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.

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

Although many homeowners may view the hair bittercress a pest, the plant is edible and has other good attributes. Hairy bittercress is rich in antioxidants and some people use it as substitute for parsley when cooking. Hairy bittercress is a member of the mustard family and spreads by seeds that are dispersed as the pods burst open explosively after maturing. The seeds usually germinate in late summer or early fall and seedlings remain dormant until the weather warms up in early spring and they grow quickly, producing white flowers.

These short-lived plants have shallow root systems that readily respond to hand-weeding or cultivation. Applying a good mulch prior to germination of hairy bittercress is recommended in flower beds to proactively manage the weed. Actively growing weeds can be easily hand-weeded by taking advantage of their shallow root system. If you are finding hairy bittercress on your lawn, chemical control is an option that involves applying a preemergence herbicide in late summer before the seeds germinate or applying postemergence herbicide to young and actively growing weeds in lawns. Keep in mind that applying most herbicides applied over top may cause injury to ornamentals. Preemergence herbicides effective on lawns include isoxaben (Gallery) and oxadiazon (Ronstar) and those in flowerbeds include oryzalin (Surflan), isoxaben + trifluralin (Snapshot). Postemergence herbicides to control this weed in lawns include a combination of triclopyr (Turflon), carfentrazone + 2,4-D (Speedzone). If using a preemergence herbicide, especially in fall, it may be a good idea to include a postemergence herbicide such as triclopyr or 2, 4-D to control seedlings.

Benefits of Hairy Bittercress

You also will find these tips useful in addressing other winter annuals such as purple deadnettle, henbit, common chickweed and mousear chickweed. Be sure to read all of the labels carefully before applying an herbicide to ensure that it is safe on the plant material used for and effective for the weed to be controlled. Specialty herbicides, especially certain pre-emergence herbicides, may not be readily available in retail stores. Once you have treated the area, you can reseed the grass to prevent other weeds, such as crabgrass, from establishing in that area.

Warmer temps and spring-like weather are welcomed by many. But, with this nice weather comes lawn/garden weeds, and they can take off swiftly, providing a limited window of opportunity for homeowners to get them under control. Once such weed is hairy bittercress. Common in West Virginia lawns and gardens, this weed is a winter annual that grows predominantly in spring but is capable of germinating and growing year-round under suitable environmental conditions.

Author: Rakesh Chandran, WVU Extension Weed Science Specialist
Last Reviewed: May 2018