Horkelia sericata
Horkelia tridentata
Howell's horkelia, silky horkelia
cluster horkelia, three-tooth horkelia
ascending to erect, 1.5–4.5 dm, hairs 1 mm proximally, glands absent or sparse distally.
decumbent to nearly erect, 0.5–4(–7) dm, hairs 1–3 mm proximally, glands absent or sparse distally.
± cylindric to weakly planar, 3–10 × 0.3–1.2 cm, densely sericeous, often villous on margins apically;
stipules usually entire or forked, rarely pinnately divided into linear lobes;
leaflets (8–)10–20 per side, ± overlapping, elliptic to flabellate, 2–8 × 1–4 mm, 1/2–2/3 as wide as long, divided ± 1/2+ to midrib into (0–)2–4 elliptic lobes 1–2 mm wide, these not restricted to apex.
planar, 3–12 × 1–3(–4) cm, usually sericeous to villous, sometimes glabrate adaxially;
stipules entire or rarely forked or pectinate;
leaflets 2–5(or 6) per side, separate to slightly overlapping, elliptic to cuneate-oblong, (3–)5–20(–30) × 1.5–7(–10) mm, (1/4–)1/3–1/2 as wide as long, divided 1/10–1/6 or less to midrib into (0–)3(or 4) triangular teeth 1 mm wide, these restricted to apex.
(2 or)3–5;
stipules 3–8 mm, entire or shallowly 1–2-toothed.
1–5;
stipules 3–12 mm, entire or deeply 3–5-lobed, lanceolate to ovate.
open, flowers arranged individually and/or in non-capitate glomerules.
open to congested, flowers arranged in ± capitate glomerules or in ± corymbiform clusters.
1–4 mm.
(1–)2–6(–10) mm.
10 mm diam.;
epicalyx bractlets linear-lanceolate, 1.5–3 × 0.5 mm, ± 2/3 length of sepals;
hypanthium 1–1.5 × 2–3 mm, ± 1/2 to as deep as wide, interior glabrous;
sepals spreading to reflexed, abaxially green to reddish or purplish, 2–4 mm;
petals white to pink or red-veined, narrowly obcordate, 3–4.5(–7) × 2–3 mm, apex ± emarginate;
filaments 0.5–1.5 × 0.2–0.5 mm, anthers 0.4–0.6 mm;
carpels 2–6;
styles 1.5–2 mm.
4–10 mm diam.;
epicalyx bractlets linear to narrowly elliptic, 0.8–2(–3) × 0.2–0.4 mm, 1/2–2/3 length of sepals;
hypanthium 1–2.5 × 2–5 mm, 1/2 to nearly as deep as wide, interior glabrous or pilose;
sepals moderately reflexed, abaxially green to reddish, 1.5–3 mm;
petals white, sometimes tinged with pink, linear to broadly oblanceolate, (1–)1.5–4(–4.5) × 0.3–1.5 mm, apex acute to rounded or mucronate;
filaments 0.5–2 × 0.1–0.4(–0.8) mm, anthers 0.2–0.5 mm;
carpels 5–15;
styles 1–2.5 mm.
brown, 2–2.5 mm, smooth.
light brown, 1.5–2.5 mm, rugose.
= 28.
Horkelia sericata
Horkelia tridentata
Of conservation concern.
D. D. Keck (1938) expanded the circumscription of Horkelia sericata to encompass the plants segregated here as H. howellii, on the grounds that intergradation is too extensive to justify taxonomic recognition of the extremes. In this evaluation, however, most collections can be unequivocally divided between plants with compact silvery-sericeous leaves with entire or forked stipules (H. sericata), and plants with larger, greener leaves and pinnately divided stipules (H. howellii). It is not known if the chromosome count provided by P. A. Munz (1959) was derived from H. howellii or H. sericata.
As here circumscribed, Horkelia sericata is a localized taxon known only from Curry County, Oregon, and the Gasquet serpentine area in adjacent Del Norte County, California.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Varieties 2 (2 in the flora).
Rydberg established Horkelia flavescens on the basis of its more congested inflorescence, purportedly yellowish petals, and broader filaments. As noted by D. D. Keck (1938), the petals are usually white, at least when fresh, and the other characters are highly variable; he reduced H. flavescens to a subspecies of H. tridentata, which is here treated at the rank of variety. In general, var. flavescens tends to be more decumbent with a single, loosely congested flower cluster and broader petals; these characters completely overlap and can vary independently. The presence or absence of hairs on the hypanthium interior is the single most reliably diagnostic character and is the primary determiner of the geographic distributions presented here. The exception is a cluster of populations from the extreme southern end of the coastal range of var. flavescens in Colusa, Lake, and Mendocino counties, California, which have glabrous hypanthia but otherwise have all the diagnostic characters of var. flavescens. Although provisionally included here within var. flavescens, these populations may be better treated as a separate variety.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Hypanthium interior glabrous; petals linear to oblanceolate, usually ± equal to or longer than sepals; inflorescences composed of 1+ ± capitate glomerules, these sometimes expanding with age. | var. tridentata |
1. Hypanthium interior pilose (except in some North Coast Ranges of California); petals ± broadly oblanceolate, often shorter than sepals; inflorescences composed of usually 1 ± corymbiform cluster. | var. flavescens |
CA
OR
Flora NW
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
