Streptanthus insignis is an uncommon species of flowering plant in the mustard family known by the common names plumed jewelflower[1] and San Benito jewelflower.

It is an annual herb producing a hairy, bristly, branching stem up to about 60 centimeters long.

Each fertile flower has a bell-shaped calyx of sepals which is purple or greenish-yellow depending on subspecies.

The petals at the tip are purplish or yellowish, also depending on subspecies.

[2] This taxon has greenish yellow flowers, sometimes tinged with purple.