Heart-Podded Hoary Cress (Cardaria Draba), Lens-Podded Whitetop (Cardaria Chalepensis) and Hairy Whitetop (Cardaria Pubescens) are B-rated weeds of very limited distribution in Fresno County. All species are deep rooted perennial herbaceous plants that grow up to 2 feet tall. They will reproduce by seed and root fragments. In the early spring, the plants emerge from the roots as a rosette. Flowering occurs early summer to fall. Hoary cress forms a cluster of small white flowers with four petals. The C. draba flower produces a heart shaped bladder-like seed capsule containing two reddish-brown seeds. C. chalepensis produces a lens-podded seed capsule, and C. pubescens produces a hairy globe-podded seed capsule. Seeds are set by mid- summer. All hoary cress species are distinguished from perennial pepperweed by the leaf attachment to the stem. Hoary cress leaves clasp the stem while perennial pepperweed leaves do not (see below).
Hoary Cress Along Highway 33 (Left), Closeup of Flower Head (Right)
Hoary Cress Next to an Alfalfa Field (Above)
Hoary cress is a non-native invasive noxious weed species that is native to Europe.
It will readily infest disturbed soils. Hoary cress is a perennial pest in alfalfa. Livestock that ingest large quantities can develop digestive problems. It is very common in alkaline soils and is highly competitive with other species once it becomes established.
Yearly, during February, the Fresno County Department of Agriculture staff will begin noxious weed surveys for hoary cress, a B-rated noxious weed of very limited distribution in Fresno County. Known hoary cress infestations are northwest of Firebaugh and in the Dinkey Creek area.