Perennials, rhizomatous, solitary to weakly colonial, rhizomes forming a mass, yellowish, branching, filiform. Stems erect-ascending, usually freely branched, 2–35 cm, glabrous or sparsely stipitate-glandular to short glandular-villous. Leaves cauline; petiole 0–25 mm, distals 0 mm; blade palmately 3–5-veined, ovate to lanceolate-triangular or narrowly lanceolate (broadly ovate in large-leaved forms), 5–35(–55) mm, base cuneate to attenuate, margins irregularly denticulate, apex acute to obtuse or rounded, surfaces glabrous, sparsely stipitate-glandular to short glandular-villous, glabrate, or sparsely to moderately villous, hairs thick-vitreous, eglandular. Flowers herkogamous, 1–3(–5), from distal nodes. Fruiting pedicels 15–35(–40) mm, sparsely stipitate-glandular to short glandular-villous. Fruiting calyces usually purple-tinged and purple-dotted, broadly campanulate, inflated, sagittally compressed, 11–15 mm, glabrous or sparsely stipitate-glandular to short glandular-villous, villous at sinuses, throat closing, lobes broadly ovate, abaxial usually longer than lateral, adaxial at least 2 times as long as others. Corollas yellow, red-dotted, bilaterally symmetric, bilabiate; tube-throat broadly funnelform, 15–28 mm, exserted 5–10 mm beyond calyx margin; limb expanded 14–30 mm. Styles hirtellous. Anthers included, glabrous. Capsules included, 5–7 mm. 2n = 28, 56.
Phenology: Flowering Jul–Sep.
Habitat: Seeps, springs, stream banks, shallow rivulets, cliff bases, ledges and crevices, steep gravelly slopes, wet meadows.
Elevation: 1400–3400 m.
Alta., Ariz., Calif., Idaho, Mont., Nev., Oreg., Utah.
Plants of Erythranthe tilingii are characterized by their relatively low stature and stems arising from a system of thin rhizomes and producing mostly one to three large flowers each; they usually occur at relatively high elevations. Erythranthe tilingii sometimes has been considered to include one or several infraspecific entities; from within this taxonomic amalgam, four distinct species are recognized here: E. caespitosa, E. corallina, E. minor, and E. tilingii. Erythranthe corallina and E. minor probably are more closely related to E. guttata. The populations identified here as E. tilingii from northeastern Oregon northeast to Alberta and southeast to Utah may prove to be a separate (undescribed) species.
Erythranthe tilingii in the strict sense is relatively widespread over the western United States and is sympatric with E. caespitosa and E. corallina. Leaves in E. tilingii are variable in size, and particularly in Idaho, they may approach the small size of those of E. caespitosa, but the leaf margins of E. tilingii are distinctly toothed, and the stems are taller and more erect. Across the range of the species, plants sometimes produce very large leaves, but these often occur on plants with characteristically smaller leaves. This wide variability in size apparently does not occur in E. caespitosa.