Hymenoxys ambigens is a species of flowering plant in the daisy family known by the common name Pinaleño Mountains rubberweed.

[2][3] Hymenoxys ambigens is a perennial herb up to 150 cm (5 feet) tall.

Leaves have very narrow lobes resembling branching threads.

[4][5] In 1882, Sarah Plummer Lemmon discovered the species.

Harvard University botanist, Asa Gray, first described the species, naming it Plummera floribunda in her honor.