Marin Master Gardeners
University of California
Marin Master Gardeners

Stop the popping - Controlling hairy bittercress

Hairy bittercress (Cardamine hirsute)
Hairy bittercress (Cardamine hirsute)
Have you ever had the experience of pulling a small weed and setting off an explosion of seeds in all directions? The likely culprit is hairy bittercress (Cardamine hirsute), which starts proliferating with the winter rains. It appears as a small, flat rosette of leaves and quickly produces small white, four-petal flowers on wiry green stems. The trick is to pull it at this stage or, better yet, before it flowers. Seemingly overnight, the flowers form siliques, or needle-thin seed pods, which explode at the slightest touch, sending seeds in all directions. It’s especially problematic when the seed pods pop near a brick or stone walkway, because bittercress can establish itself easily between the cracks and become very difficult to eradicate.

Bittercress thrives in moist conditions and disturbed soil. It’s common to unknowingly bring it home in nursery containers, so some gardeners make a practice of gently scraping off the top inch or two of soil in the pots before planting. Dispose of the scraped-off soil in your green can.

Bittercress is a member of the mustard family and is widely distributed around the U.S. The clumps can reach four to eight inches in height, but stay much smaller with less moisture. Go on patrol for this pesky weed once or twice a week during the winter and spring. It’s easy to hand pull. Once the seeds pop, you’ll be fighting a much bigger crop next year.

Contributor: Faith Brown

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