Hairy Bittercress Life Cycle: Stages of Growth

Hairy bittercress (Cardamine hirsuta) is a widespread cool-season annual from the mustard family that frequently appears in lawns, garden beds, and container plants. Native to Eurasia, it has become common across North America. Its success comes from its ability to grow and reproduce quickly, often becoming one of the first weeds seen in the spring. Understanding its progression is helpful for managing its presence in cultivated spaces.

Germination and Rosette Stage

The life of a hairy bittercress plant begins with a seed sprouting in the soil. Germination most often occurs in the cool, damp conditions of autumn or early spring. Peaks in emergence have been noted from late summer into winter, with seeds able to sprout from April through December in some climates. Seedlings that emerge in the fall can withstand even severe frosts.

Following germination, the plant develops a basal rosette, a flat cluster of leaves growing low to the ground. The compound leaves are made up of two to eight alternately arranged leaflets with a larger, rounded leaflet at the terminal end. These leaves often have tiny hairs on their surfaces, which is the source of the plant’s common name. During this phase, the plant establishes a shallow, fibrous taproot system.

Bolting and Flowering Stage

As temperatures rise in the spring, the plant transitions from vegetative growth to its reproductive phase. This change is marked by “bolting,” where one or more slender, upright stems emerge from the center of the basal rosette. These mostly smooth, angled stems can grow up to 30 centimeters tall and branch primarily from the base. The basal leaves typically remain on the plant as it matures.

At the ends of these stems, clusters of small flowers appear. True to its place in the mustard family, each flower has four white petals arranged in a cross shape. Hairy bittercress is self-pollinating and can flower for an extended period, mainly from March through August, though it can be found blooming year-round in some locations.

Seed Production and Dispersal

After the flowers are pollinated, the plant produces long, narrow seed pods, known as siliques, which develop and stand upright along the stems. Each silique contains around 20 seeds, and a single plant can produce between 600 and 1,000 seeds on average.

The siliques are dehiscent, meaning they are built to split open to release their contents. When the pods mature, or if they are disturbed by touch, wind, or raindrops, they burst explosively. This action can launch the small seeds up to one meter away from the parent plant. The seeds become sticky when wet, which can further aid in their dispersal.

Life Cycle Timeline

Hairy bittercress functions as a winter annual, completing its entire life cycle in less than a year. The parent plant dies after it has dispersed its seeds. Under optimal conditions, the full cycle from germination to seed dispersal can be completed in as little as five to six weeks. The timeline can vary, with some plants behaving as summer annuals or even biennials. This rapid development means that multiple generations can be produced within a single year.