Erythranthe lewisii is a perennial herb, with stem length ranging from 25 to 80 cm and individual leaves ranging from 20 to 70 mm. The vegetative tissue is covered with fine hairs. 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. Occasional populations of white-flowered individuals (which do not express
anthocyanin pigments in the corolla) are known. ==Taxonomy==