Cardamine

Bittercress (Cardamine spp.), in the Brassicaceae (mustard) family, are common cool-season weeds, but can persist and spread year round in shaded, moist environments.  Plants form a basal rosette of leaves. The flowers are white and form small, cigar-shaped fruit. Plants are prolific seed producers and seeds are forcefully expelled 3 to 6 feet. Freshly-shed seed have no dormancy. 

Among the numerous varieties, Cardamine pensylvanica or Pennsylvania bitter-cress is an annual that can be found in the New England states of Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island and Vermont.  Its habitat includes wetlands.  Its lobed leaves are compound and alternate.  You will find one leaf per node along the erect stem.  Its flowers have 4 white petals.  The fruits are dry and will split open when ripe.  

The annual or biennial Cardamine oligosperma grows in western US states.  Alaska, Washington, Oregon, California and eastward to the Rocky Mountains are common locations where it is found in seasonally wet forests and open land.  Flowering is in the form of racemes.  Its numerous, hairy leaves are alternate with 4 to 10 lateral leaflets.  

A perennial, Cardamine pratensis, is not considered to be invasive, as other varieties are classified.  Known as the cuckoo flower, it is abundant in Canada, and the Midwest states of Minnesota, Illinois south to Virginia.  Its foliage is compound and edible.

Propagation is by way of the plant's Dehiscent seed pod, that is a pod that splits open when ripe, disbursing its seed.

Wildlife Value:  Members of the genus Cardamine support the following specialized bee: Andrena (Scaphandrena) arabis.

Insects, Diseases, and Other Plant Problems: Plants often harbor whitefly and mites and have been implicated as alternative hosts for some diseases. Seedlings are numerous, small, and are time-consuming to hand remove.  Do not let plants go to seed. Manage bittercress populations around the property to prevent spread. Inspect all new plant materials for infestations of this weed. Bittercress is well managed by available preemergence herbicides but due to its prolific seed production and continuous germination it continues to be a challenging weed.  Powdery mildew, downy mildew and rust are minor issues.  It is listed as an invasive species in some parts of the US including HI and GA.