First Wildflower of 2011: Hairy Bittercress (Cardamine hirsuta)

I’d seen a few rosettes of Hairy Bittercress (Cardamine hirsuta) in areas of the field at home that were protected from radiant cooling at night. After finding the Hairy Bittercress with buds at Little Mulberry Park in Gwinnett County, I searched at home and found one plant with buds. During the following week, I found five or so more. Then, last Saturday, I found a single plant at the front end of the field that not only was sheltered from radiant cooling at night but also received a lot of sun during the day. This precocious plant had five flower stalks.

The plant.

A closer view of the florets on one stalk. Seed pods are already developing from the centers of some florets.

A closer view of the florets on the most developed stalk.

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A view of a stalk in with developing seed pods. One seed pod already shows swelling due to the developing seeds.

The seed pods will develop rapidly and spray the seeds when the pod splits open suddenly at the slightest touch. The following photographs were taken in 2010.

A stalk with developing seed pods.

Ripe seed pods.

It's almost impossible to touch ripe seed pods without the pods ‘exploding.’ The pod springs open. One half of the pod remains attached to the stalk and the other half detaches at the top and curls up rapidly spraying the seeds through the air. The seeds are sticky and adhere where they fall. This photograph shows the seeds and the halves of seed pods that have curled up when the pods sprang open.
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Distribution Map:
- University of North Carolina Herbarium: Cardamine hirsuta – Hairy Bittercress
- United States Department of Agriculture Plants Database: Cardamine hirsuta (Hairy Bittercress)

Identification resources:
- Shedi de botanica: Cardamine hirsuta – Hairy Bittercress
- Native & Naturalized Plants of the Carolinas and Georgia: Hairy Bittercress (Cardamine hirsuta)

Related posts:
- 2010: Year Of The Wildflower – Wildflower Index
- Hairy Bittercress (Cardamine hirsuta)

Hairy Bittercress (Cardamine hirsuta)

I spotted the characteristic rosettes of Hairy Bittercress (Cardamine hirsuta) by the pool at the creek on January 10th. At first I mistook them for Shepherd’s Purse (Capsella bursa-pastoris) although the rosette of this plant is distinctly different.

These plants led a hard life. They were submerged under a couple of inches of water for a couple of days in two successive rounds of flooding. In this photograph, you can see plants just starting to bloom (white spots).

The plants maintained their rosette shape for some time. At first a single flower spike develops.

Then they send up several flower spikes and the plant loses its distinct rosette shape and becomes more ‘bushy.’

The flower petals open up for a short time.

More often the flower petals appear to ‘close’ as seedpods develop. The leaves on the flower stalks are quite different from the rosette leaves.

Ultimately the plants appear to be a cluster of bare stems. The flowers are almost invisible among the forest of stems.

Hairy Bittercress was introduced from Europe and is considered a weed, distribibuted throughout the Unites States and Canada, and difficult to eradicate. I’m not sure that I mind. In addition to finding it at home, I have found them on the lake side of the dam as well as on the plateau between the pedestrian bridge and the gas line in Fort Yargo State Park.
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Identification resources:
- Shedi de botanica: Cardamine hirsuta – Hairy Bittercress
- Shedi de botanica: Capsella bursa-pastoris – Shepherd’s Purse
- Cardamine hirsuta

Related posts:
- Whitehall Lake: Wildflowers