Western water-hound is a perennial wildflower with erect, simple or branched stems from 20-80 cm high arising from tuberous rhizomes. The stem is covered with spreading hairs below, less so above, or with spreading hairs along the 4 edges of the square stems. The leaves range from glabrous to rough or covered with short to long, stiff hairs on the upper surface of the blade. The leaves are opposite on the stems, only slightly reduced in size upwards on the stem, and often oriented at an angle to the pair above and below them. The blades are elliptic in outline, measuring from 3.5-10 cm long and 0.6-3.5 cm wide. Most leaves are sessile or nearly sessile, with a few tapering gradually to a short petiole. The margins are evenly but coarsely toothed.
The inflorescence consists of clusters of flowers arising from the axils of the upper leaves. The 5 calyx lobes are narrowly triangular with a prominent midnerve, and distinctly longer than the mature nutlets after flowering. The white corolla is 4-lobed, with three the same size and one broader than the others. The corolla is 3-5 mm long, barely extending past the calyx.
Western water-horehound may be found at lower elevations in the valleys in moist soils in marshes and along the shores of rivers, lakes and streams.
Western water-horehound may be found from southern British Columbia south across the Pacific Northwest (to the east of the Cascade Mts.) to California and east to Saskatchewan, Minnesota, Iowa and Colorado.