Circaea pacifica Ascherson & Magnus, Bot. Zeitung (Berlin) 29: 392. 1871; C. alpina var. pacifica (Ascherson & Magnus) M. E. Jones

Stems firm, terete, remaining mostly unflattened after pressing, pubescent with at least a few recurved, falcate hairs. Leaves: petiole 1.5–5 cm; blade 3–7.5(–11) × 2.5–5.5(–8) cm, margins subentire to minutely denticulate, base usually rounded to subcordate, rarely cordate, apex acute to short acuminate. Inflorescences usually densely, less often sparsely, glandular puberulent. Flowers clustered at apex of raceme, opening before elongation of raceme axis; floral tube 0.3–0.6 mm; apical notch of petal 1/4–1/3 length of petal; pedicel and mature fruit combined length 3.5–6.5 mm. 2n = 22.

Flowering summer. Cool, temperate deciduous and mixed forests, forest margins, along streams; (0–)200–2700(–2900) m; Alta., B.C.; Alaska, Ariz., Calif., Colo., Idaho, Mont., Nev., N.Mex., Oreg., Utah, Wash., Wyo.

Subspecies pacifica and subsp. alpina are easily separated by the stems with at least a few hairs and by the minutely denticulate to nearly entire leaf blade margins in subsp. pacifica. The stems of subsp. pacifica remain unflattened in herbarium specimens, whereas the stems of subsp. alpina are flattened and appear to be very narrowly winged after pressing. Subspecies pacifica is usually larger and more robust than subsp. alpina and is similar to some of the Asian subspecies of Circaea alpina in its somewhat thicker, deeper green leaves and less delicate stems. Plants in the areas where the two subspecies are sympatric are sometimes difficult to assign to one subspecies or the other, the few minute hairs on the stem being the most reliable distinguishing feature.