Balsamorhiza macrophylla


Trans. Amer. Philos. Soc., n. s. 7: 350. 1840

Synonyms: Balsamorhiza hookeri var. idahoensis (W. M. Sharp) Cronquist Balsamorhiza macrophylla var. idahoensis W. M. Sharp
Treatment appears in FNA Volume 21. Treatment on page 98. Mentioned on page 94, 95.
Plants 30–45(–100) cm. Basal leaves green, ovate to lanceolate, 20–50+ × 8–15 cm (pinnatifid, lobes lanceolate, 20–80+ × 10–40 mm, entire or ± dentate), bases ± cuneate, ultimate margins usually entire (plane or weakly revolute, ciliate), apices obtuse to acute, faces scabrous or piloso-hirtellous to pilose (at least abaxial usually gland-dotted as well). Heads usually borne singly. Involucres ± hemispheric, 20–30 mm diam. Outer phyllaries lance-ovate or lanceolate to lance-linear, 12–30(–40) mm, equaling or surpassing inner (margins ciliate), apices acute to attenuate. Ray laminae 35–50+ mm. 2n = 100 ± 2.

Phenology: Flowering May–Jul.
Habitat: Deep soils, rocky meadows, sagebrush scrublands, conifer forests
Elevation: 1000–2400 m


Balsamorhiza macrophylla is a high polyploid; it occurs sympatrically with B. sagittata. It evidently arose from hybridization between B. sagittata and B. hispidula. Balsamorhiza macrophylla has the multi-branched caudices and massive taproots of the former, and the leaf dissection of the latter. No hybrids with other species are known. Presumably, the high-polyploid chromosome complement precludes interbreeding. Plants of </i>var.<i> idahoensis are smaller, are known only from southwestern Idaho and northeastern Utah, and differ from var. macrophylla by being pilose, with strongly shaggy-pilose involucres. More study may determine that </i>var.<i> idahoensis merits specific rank. The Utah populations are not well understood and deserve attention.

Lower Taxa

No lower taxa listed.