Bittercress

Image by: James Altland, USDA-ARS
Bittercress can be problematic in container nursery settings.
Image by: James Altland, USDA-ARS
Image by: James Altland, USDA-ARS
Bittercress flowers occur in terminal racemes, with each flower having 4 white petals.
Image by: James Altland, USDA-ARS
Image by: James Altland, USDA-ARS
Seed pods on bittercress are called siliques. Each silique generates about 30 seeds, and each bittercress plant can generate up
Image by: James Altland, USDA-ARS
Image by: James Altland, USDA-ARS
Bittercress seedlings can germinate in large numbers on the gravel floor of a greenhouse or hoophouse.
Image by: James Altland, USDA-ARS
Image by: James Altland, USDA_ARS
Bittercress seeds stick to containers walls and germinate readily.
Image by: James Altland, USDA_ARS
Cardamine oligosperma
Family: 
Brassicaceae
Life cycle: 
Annual
Habit: 
Plants form a small mounded clump generally 4 to 8 inches tall and wide. However, during warm summer months, bittercress generally grow much smaller. Often, many seedlings germinate in a small area so that they appear as a large, dense mat. Several branched, smooth stems emerging from the soil line. Leaves radiate from the base of the stem, forming a rosette. Each leaf generally contains 4 to 8 leaflets arranged alternately along the rachis.
Flowers: 
Flowers occur in racemes. Each flower has 4 white petals, generally 3 to 5 mm in diameter.
Favorable environments: 
Container
Favorable environments: 
Field
Favorable environments: 
Greenhouse
Favorable environment notes: 
Bittercress thrives in moist environments, such as propagation benches and flats, greenhouse floors, gravel container areas, landscape areas; any areas that receive consistent moisture. Bittercress will germinate and grow throughout the year due to the cool environment provided by daily irrigation in container crops.
Dissemination: 
Bittercress flowers form narrow pods (1/2 to 3/4 inch long) called siliques. When pods mature, they split open into two curling valve-like structures and explosively project seed up to several yards away. Sanitation of nursery pots and propagation flats is essential to prevent the spread and potential infestation of bittercress. Keeping clean areas and pots during propagation can be the most effective means of controlling bittercress throughout the entire nursery.
Of interest: 
It has been reported that bittercress plants are capable of producing over 5000 seed, most of which can germinate within 2 weeks after being dispersed. Seeds that don't land in pots or geminate can easily spread via irrigation or rain runoff, on the soles of workers' shoes, or they can be transported on unwashed pots. Early detection of bittercress is important because herbicides are most effective at the seedling stage. If seedlings are present, they can also serve as a host for aphids. As stated previously, sanitation is an essential component to managing bittercress in the nursery setting.