Horkelia tenuiloba
Horkelia clevelandii
Santa Rosa, Santa Rosa horkelia, Sonoma horkelia, thin-lobed, thin-lobed horkelia
Cleveland's horkelia
ascending to erect, 1–4 dm, hairs ± spreading.
weakly planar to ± cylindric, 5–15(–20) × 0.5–1.5 cm;
stipules entire;
leaflets 8–16(–20) per side, ± overlapping especially distally, cuneate to flabellate, 3–10 × 2–10 mm, 1/2 to nearly as wide as long, divided 1/2–3/4+ to midrib into 3–8 linear to narrowly oblanceolate or narrowly elliptic lobes, sparsely villous at least marginally, often with a tuft of hairs apically.
2–5.
open to congested, flowers arranged individually and in glomerules, these sometimes subcapitate.
1–6 mm.
10 mm diam.;
epicalyx bractlets narrowly to broadly lanceolate, 1–3 × 0.5–1 mm, slightly shorter than sepals, entire;
hypanthium 1–1.2 × 2.5–4.5 mm, less than 1/2 as deep as wide, interior pilose;
sepals spreading to reflexed, lanceolate, 3–5 mm;
petals oblanceolate, 2.5–4.5 × 1.5 mm, apex emarginate;
filaments (1–)1.5–2 × 0.5 mm, anthers 0.4–0.6 mm;
carpels 10–25;
styles 1.8–2.2 mm.
light brown, 1.5 mm, smooth or slightly rugose.
= 28.
Horkelia tenuiloba
Horkelia clevelandii
Of conservation concern.
Horkelia tenuiloba occurs on the western edges of the northern Coast Ranges in Marin, Mendocino, and Sonoma counties. Populations from San Luis Obispo formerly included in this species now are part of H. yadonii. A specimen (M. K. C[urran], July 5, 1885, UC) unequivocally of H. tenuiloba purportedly from San Luis Obispo is in all likelihood mislabeled with respect to locality.
Horkelia tenuiloba is commonly associated with seral openings in chaparral and woodlands and might be dependent on periodic disturbance by fire.
W. L. Jepson (1909–1943, vol. 2) used Potentilla stenoloba (1895) for the species encompassing the types of Horkelia tenuiloba and P. micheneri. The epithet micheneri (1893) has priority at species rank within Potentilla, since P. tenuiloba (Torrey) Greene is a later homonym of P. tenuiloba Jordan.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Varieties 2 (1 in the flora).
The component of Horkelia clevelandii occurring in the Sierra San Pedro Mártir and most of the Sierra Juarez of northern Baja California, Mexico, is var. brevibracteata (Wiggins) Ertter & Reveal. It differs from var. clevelandii in tending to have a more compact and matted habit, shorter stems (1–3 dm), more numerous (11–16) pairs of smaller (4–8 mm) leaflets, shorter epicalyx bractlets (1.5–2 mm), and deeper hypanthia (2–2.5 mm).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
CA
WildflowerSearch
iNaturalist
USDA Plants Database
