Together with other species in Erythranthe, it serves as a model system for studying pollinator-based reproductive isolation.

The flowers are medium in size, set on fairly long (30–70 mm) pedicels, and range in color from pale pink (generally found in the Sierra Nevada populations, sometimes separated as Erythranthe erubescens G.L.Nesom) to dark magenta (more common in the Cascade Range and Rocky Mountains populations), with a central pair of carotenoid-rich yellow nectar guides covered in trichomes on the lower lobe of the corolla.

[citation needed] Occasional populations of white-flowered individuals (which do not express anthocyanin pigments in the corolla) are known.

[6][7][8] Erythranthe lewisii is native to western North America from Alaska to California to Colorado, where it grows in moist habitat such as stream banks,[9] and is generally found at higher elevations in montane areas.

[10] Erythranthe lewisii is pollinated by bees (primarily Bombus and Osmia), which feed off of its nectar and transfer its pollen.