Thlaspi californicum is a rare species of flowering plant in the family Brassicaceae[1] known by the common name Kneeland Prairie penny-cress.

The inflorescence is a raceme of mustardlike flowers with white spoon-shaped[3] petals just under a centimeter in length.

In the area there are three colonies growing on separate serpentine outcrops on the prairie.

[2] This plant is threatened by development at the airport and other facilities nearby, including roads and a helitack base.

Planned expansion projects at the airport, including installation of a parking lot, may reduce the amount of suitable habitat further.