Rogue River horkelia

Horkelia caruifolia Rydberg ex Howell, Fl. N.W. Amer., 181. 1898; Potentilla caruifolia (Rydberg ex Howell) Crum; P. caruifolia var. divergens Crum

Plants rosette-forming to ± matted. Basal leaves green to grayish, (4–)5–9(–15) cm; leaflets 5–10(–15) mm, lobes 4–15, linear, 0.4–1 mm wide. Pedicels 2–7(–10) mm, puberulent, eglandular. Flowers: petals broadly obcordate, (3.5–)5–8 × (4–)5–8 mm; filaments 2–3 mm.

Flowering summer. Grassy openings in mixed oak and conifer woodlands, on non-serpentine soil; 400–1100 m; Oreg.

Except for a single population in extreme southeastern Klamath County (noted under var. daucifolia), all populations of Horkelia daucifolia from Oregon are here referred to var. caruifolia (B. Ertter and J. L. Reveal 2007). The variety is found in the Rogue River drainage in Jackson and Josephine counties and might prove to be of conservation concern. Collections from near Ashland, including the type of H. caruifolia, are not as distinct from var. daucifolia as are populations from north of the Rogue River Valley, which have particularly broad petals and mat-forming capabilities. These northern populations include the type of Potentilla caruifolia var. divergens, which was described on the basis of its widely open inflorescence; subsequent collections from the same general area (near Trail) have the full range of inflorescence compactness found elsewhere in H. daucifolia.