Hairy bittercress A native, annual to biennial plant found in open and cultivated ground, and on rocks and walls throughout the UK. Hairy bittercress is recorded up to 3,800 ft. It is a common Late winter and spring signal growth of all plants but especially weeds, like hairy bittercress weed. What is hairy bittercress? This article explains more as well as how to keep the weed under control. Hairy bittercress is an annual weed that can spread quickly.
A native, annual to biennial plant found in open and cultivated ground, and on rocks and walls throughout the UK. Hairy bittercress is recorded up to 3,800 ft. It is a common weed of gardens, greenhouses, paths, railways and waste ground. It is a particular problem in container-raised plants from nurseries and garden centres.
Hairy bittercress is variable in size and leaf shape. Waved bittercress, C. flexuosa, closely resembles hairy bittercress and is also variable in habit. It is usually annual or biennial but occasionally perennial. A related introduced weed, New Zealand bittercress, C. corymbosa, has become troublesome in polytunnels. It is similar in appearance to hairy bittercress and has the same explosive seedpods but is generally smaller.
Hairy bittercress is found in flower all through the year but mainly from March to August. It is automatically self-pollinated. Seed is shed in May and June and sometimes into the autumn. There are around 20 seeds per seedpod. The average seed number per plant is 600 but a large plant may yield several thousand seeds. Plants can be found in fruit for 8 months of the year.
There is little germination of the fresh seeds. The seed after-ripens at high temperatures. The higher the temperature the greater the temperature range at which subsequent germination will take place. Germination is increased by a period of dry storage.
Hairy bittercress seed germinates from April to December. There are peak flushes of seedling emergence from July to August and November to December but this varies in different years. Autumn is the main period of seedling emergence. Hairy bittercress can complete its lifecycle in 5-6 weeks. The cycle is longer in rich soils and shorter in poor ones. Seedlings can survive the severest frost.
Hairy bittercress forms a relatively persistent soil seedbank.
When the seedpods are ripe the seeds are dispersed explosively for up to 1 m if the plants are shaken by the wind or by weeding operations. The seeds become sticky when wet and can be spread on tools and clothing.
Seedlings should be killed by early cultivations and regular hoeing to prevent hairy bittercress plants flowering and setting seed. Stem fragments are capable of re-rooting following cultivation in moist conditions. Hairy bittercress seedlings should be removed from container plants before the weed can set and shed seeds. The standing areas must also be kept weed-free. Improved drainage may discourage this moisture-loving weed.
Hairy Bittercress Killer: Learn More About Control For Hairy Bittercress
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 bittercress 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.
Hairy bittercress: A weed to watch out for
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) become 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.
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.