Cutleaf Balsamroot

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 var. 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 var. idahoensis merits specific rank. The Utah populations are not well understood and deserve attention.

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.

Balsamorhiza hookeri Nuttall var. idahoensis (W. M. Sharp) Cronquist; B. macrophylla var. idahoensis W. M. Sharp

Balsamorhiza macrophylla (cutleaf balsamroot) is a North American species of plants in the tribe Heliantheae of the family Asteraceae. The species is native to the northwestern United States, in Idaho, Montana, Wyoming, Utah, and Oregon. It grows in sagebrush scrublands and conifer forests. It sometimes hybridizes with Balsamorhiza sagittata.

B. macrophylla grows up to 100 centimetres (39 in) tall, with leaves reaching 60 cm (24 in). It has yellow flower heads about 8–10 cm (3–4 in) in diameter, usually borne one at a time, with both ray florets and disc florets.