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weed that shoots seeds

Weed of the Month: Hairy Bittercress

As winter warms to spring, a favorite weed of foragers starts to emerge in rather cute clumps—it’s hairy bittercress! It has actually been lurking near the surface all winter, having germinated in the fall and waited out the cold temperatures before sending up flowers and seeds.

Hairy bittercress (Cardamine hirsuta) leafs out in a basal rosette, and like other members of the mustard family (Brassicaceae), its tender greens are edible. Don’t be fooled by the common name—its flavor is mild and peppery, not bitter. Though the flowers can be tough to chew, the tender leaves are suitable for a chic microgreens salad and have tons of vitamin C, calcium, magnesium, beta-carotene, and antioxidants.

The flower stalks shoot up above the rosette, topped with clusters of tiny, cross-shaped white flowers. Indeed, the former name for the family is Cruciferae, a reference to the crucifix pattern of the petals common in that family’s flowers. However, when I was little, I remember thinking these tiny flowers looked like frosty pixie wands or fairy crowns, at once earthy, tough, regal, and whimsical.

More: Learn to identify more weeds and find out more about each one by browsing the Weed of the Month archive.

While urban grazers will be most focused on the leaves, I think the seed capsules are the best part of hairy bittercress. Called siliques, they look like purplish-green toothpicks standing upright around the flower. As the seeds mature, the pods begin to coil tightly until—pop! A gentle touch or passing breeze triggers the pods to explode and send the seeds flying as far as three feet from the mother plant. This ballistic dispersal strategy, known as ballochory, is also employed by jewelweed and cranesbill.

Though hairy bittercress is originally from Eurasia and was introduced to North America, there are several species of Cardamine that are native to the United States. Several are listed as threatened or endangered, mostly due to habitat loss.

Hairy bittercress is adapted to moist, disturbed soils, so it emerges wherever we irrigate. Unsurprisingly, then, it’s a common lawn weed (where it can form expansive mats) as well as a greenhouse weed (where it pops up in and around containers). Mowing and hand weeding are the typical means of control—the shallow fibrous roots make it an easy pull. If you do pull some from your garden beds, consider making a farmer’s sandwich of cheese, apples, and a bit of fresh bittercress. Skip the compost pile and send it your stomach instead!

The Weed of the Month series explores the ecology and history of the common wild plants that most gardeners consider weeds.

Browse the Weed of the Month archives >

Saara Nafici is the executive director of Added Value/Red Hook Community Farm. She is also the former coordinator of the Garden Apprentice Program at Brooklyn Botanic Garden and a longtime activist, feminist, bicyclist, naturalist, and youth educator. Follow her weedy plant adventures on Instagram.

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Discussion

While this plant can be edible, it is also a very invasive weed here in the Missouri Ozarks where I live. I spent 2-1/2 hours pulling it one day.

Thanks so much for informing me that this greenery can be eaten! I have pulled and tossed it from a landscaped bed on a warm winter day, but no more! I’m looking forward to a farmer’s sandwich now!

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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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This spring weed is known for its tasty leaves, but it’s most interesting feature may be the way it disperses seeds by flinging them through the air.

Hairy bittercress

Hairy bittercress

hairy cress, popping cress

Cardamine hirsuta L.

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 hairy cress, popping cress Cardamine hirsuta L. A native, annual to biennial plant found in open and cultivated ground, and on rocks and walls throughout the UK.