[4] It is a perennial herb growing in clumps of several ascending or erect and hairy stems that are usually unbranching and up to 60 cm tall.

[4] The leaves are green, containing chlorophyll to undergo photosynthesis, but like other Castilleja species it is a hemiparasite, capable of tapping the roots of other plants via haustorial connections to obtain nutrients and water.

[5] The inflorescence contains bright orange to red bracts with small green flowers tucked between them.

[10] These sequestered iridoid glycosides then confer chemical protection against bird predators to the butterfly larvae.

[10] Harsh paintbrush is also one of the preferred oviposition species for female Taylor's checkerspot butterflies.