Streptanthus polygaloides is a species of flowering plant in the mustard family known by the common name milkwort jewelflower.

[1] It is endemic to the Sierra Nevada foothills of California, where it grows in woodlands and chaparral, generally on serpentine soils.

[3] This trait helps protect the plant against many types of pathogens, including the powdery mildew Erysiphe polygoni, the bacterium Xanthomonas campestris, and the fungus Alternaria brassicola.

[5] The high nickel levels in the plant have also been shown to protect it against the diamondback moth (Plutella xylostella).

[7] In fact, some insects thrive on a high-nickel diet, such as the mirid bug Melanotrichus boydi, which specializes on this plant.