What is hairy bittercress?

Hairy bittercress identification is all about timing, because this weed hides in plain sight until it’s almost too late. It’s a small winter annual in the mustard family, originally from Europe and Asia, that sprouts in fall, sits quietly as a flat rosette over winter, and flowers in the first warm days of spring.

Its trick is the seed pod. When ripe, the slender pods split open and fling seed several feet in every direction, sometimes right into your face as you reach down to pull it. One missed plant can reseed a whole bed.

Hairy bittercress identification: what to look for

Look early. By the time most people notice bittercress, it’s already setting seed.

• Rosette: a flat, ground-hugging circle of compound leaves. Each leaf has several small, rounded leaflets lined up along a stalk, with the end leaflet usually the largest.
• Stems: thin, upright, 3 to 10 inches tall, carrying a few narrower leaflets.
• Flowers: very small and white with four petals, clustered at the tips of the stems, typically March through May.
• Seed pods: narrow, upright pods about three-quarters to an inch long that stand taller than the flowers. Touch a ripe one and it snaps open.
• Roots: small and shallow. The whole plant lifts out with two fingers.

The “hairy” part is easy to miss. There are a few fine hairs on the leaf stalks and upper leaf surface, but you may need a close look to see them.

Where it grows in Pennsylvania

Bittercress loves moist soil and grows in both sun and shade. In central PA it’s especially common in mulched landscape beds, along the edges of lawns where they meet beds, in vegetable gardens and in the gaps along walks and patios.

It also hitches rides. Container plants from garden centers often carry it in the pot, and that’s how many homeowners first bring it home. Freeze-thaw winters don’t faze it; the rosettes stay green right through winter thaws and get a head start on everything else in spring.

Wet spots near downspouts and the shady north side of a house are other favorite haunts, since the soil there stays damp through fall and spring when bittercress is actively growing.

Hairy bittercress look-alikes

Shepherd’s purse is another early-spring mustard with white flowers, but its rosette leaves are lobed like a dandelion’s and its seed pods are flat little hearts. Common chickweed has opposite, pointed oval leaves on sprawling stems and white flowers whose split petals look like ten instead of four.

Yellow rocket is a mustard too, but it’s a much bigger plant with glossy leaves and bright yellow flowers. If the leaves are made of little round leaflets and the pods are thin and upright, it’s bittercress.

How to get rid of hairy bittercress

This is one weed where pulling it yourself is usually the best answer. The roots are tiny, and a few minutes on a mild winter or early spring day can clear a bed.

• Pull before flowering: rosettes come out easily, especially from moist soil or mulch. Get them in fall or the first warm weeks of spring, before the white flowers open. Once pods form, carefully pinch the plant and drop it straight into a bag so you don’t scatter seed.
• Mulch: keep 2 to 3 inches of shredded mulch in beds. Seed that lands on top has a harder time rooting, and seedlings that do sprout pull out with almost no effort.
• Check new plants: look at the soil surface of container plants before you plant them, and pick out any rosettes.
• Lawn edges: mow frequently in early spring to cut off flower stems, and keep turf thick with proper feeding and seeding.

Herbicides: Penn State notes the main challenge is timing, because bittercress flowers and seeds before most spring broadleaf sprays go down. In beds, labeled preemergence products containing ingredients such as dithiopyr, isoxaben, dimethenamid or prodiamine combinations, applied in late summer to early fall, stop the next generation before it sprouts. In lawns, postemergence broadleaf combinations with 2,4-D, dicamba, MCPP or triclopyr work on rosettes in fall. Preemergence products also block grass seed, so plan around any overseeding. Read and follow the label, since the label is the law, and check that it’s labeled for your site. Applying herbicide for hire in PA requires a PA Department of Agriculture pesticide applicator certification, so large properties go to a licensed professional.

Keeping it from coming back

The goal is simple: no plant ever gets to pop its pods. If you pull every rosette before it flowers for a couple of seasons in a row, you stop adding new seed and each year’s flush gets smaller.

Freshen mulch in beds each spring, do a quick sweep for rosettes in October and again in March, and inspect anything you bring home in a pot. That’s usually all it takes to keep bittercress a minor nuisance.

Questions we get about hairy bittercress

Similar weeds

Shepherd's PurseCapsella bursa-pastorisCommon ChickweedStellaria mediaHenbitLamium amplexicaule