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Howell's horkelia, silky horkelia

Howell's horkelia, Klamath horkelia

Habit Plants ± tufted, silvery. Plants tufted to openly matted, ± green.
Stems

ascending to erect, 1.5–4.5 dm, hairs 1 mm proximally, glands absent or sparse distally.

ascending to erect, (0.9–)1.5–5 dm, hairs 1 mm proximally, glands absent or sparse distally.

Basal leaves

± 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.

± cylindric to weakly planar, 5–15 × 0.5–1.8(–2.5) cm, usually villous to pilose at least marginally, often glabrescent;

stipules deeply 2-lobed or pinnately divided into 3–5 linear to filiform lobes that often form a tangled mass;

leaflets 10–15 per side, ± overlapping, elliptic to flabellate, (3–)4–10(–15) × 2–8 mm, 1/2 to as wide as long, divided 1/2–3/4 to midrib into (0–)2–4 elliptic to linear lobes 1–2 mm wide, these not restricted to apex.

Cauline leaves

(2 or)3–5;

stipules 3–8 mm, entire or shallowly 1–2-toothed.

(2 or)3–5;

stipules 5–12(–15) mm, entire to deeply 2–4-lobed or -toothed (usually on 1 side).

Inflorescences

open, flowers arranged individually and/or in non-capitate glomerules.

open, flowers arranged individually and/or in non-capitate glomerules.

Pedicels

1–4 mm.

1–6(–12) mm.

Flowers

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.

10 mm diam.;

epicalyx bractlets linear-lanceolate, 1–3 × 0.5 mm, ± 2/3 length of sepals;

hypanthium 1.1–1.5 × 2–3 mm, ± 1/2 to as deep as wide, interior glabrous;

sepals spreading to reflexed, abaxially green to reddish or purplish, 2.5–4.5 mm;

petals white to pink or red-veined, narrowly obcordate, 3–5 × 2–3 mm, apex truncate or emarginate;

filaments 0.5–1.7 × 0.2–0.5 mm, anthers 0.4–0.6 mm;

carpels 2–6;

styles 1.5–2 mm.

Achenes

brown, 2–2.5 mm, smooth.

brown, 2–2.7 mm, smooth.

2n

= 28.

Horkelia sericata

Horkelia howellii

Phenology Flowering summer. Flowering summer.
Habitat Chaparral, oak-conifer woodlands, on serpentine-derived soil Chaparral, oak-conifer woodlands, mainly on serpentine soil
Elevation 100–1200 m (300–3900 ft) 60–1200 m (200–3900 ft)
Distribution
from FNA
CA; OR
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; OR
[WildflowerSearch map]
[BONAP county map]
Discussion

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.)

Of conservation concern.

As noted above, Horkelia howellii comprises the bulk of what D. D. Keck (1938) and subsequent floras included in H. sericata, and the range of the latter is fully encompassed within that of the former. As here circumscribed, H. howellii occurs in northwestern California and southwestern Oregon. The handful of collections from Humboldt and Trinity counties, California, including the type of Potentilla laxiflora Drew, have leaves approaching H. daucifolia but the inflorescence of H. howellii; exact petal color is uncertain.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 9, p. 265. FNA vol. 9, p. 265.
Parent taxa Rosaceae > subfam. Rosoideae > tribe Potentilleae > Horkelia > sect. Tridentatae Rosaceae > subfam. Rosoideae > tribe Potentilleae > Horkelia > sect. Tridentatae
Sibling taxa
H. bolanderi, H. californica, H. clevelandii, H. congesta, H. cuneata, H. daucifolia, H. fusca, H. hendersonii, H. hispidula, H. howellii, H. marinensis, H. parryi, H. rydbergii, H. tenuiloba, H. tridentata, H. truncata, H. tularensis, H. wilderae, H. yadonii
H. bolanderi, H. californica, H. clevelandii, H. congesta, H. cuneata, H. daucifolia, H. fusca, H. hendersonii, H. hispidula, H. marinensis, H. parryi, H. rydbergii, H. sericata, H. tenuiloba, H. tridentata, H. truncata, H. tularensis, H. wilderae, H. yadonii
Synonyms Potentilla sericata Potentilla howellii
Name authority S. Watson: Proc. Amer. Acad. Arts 20: 364. (1885) (Greene) Rydberg: Bull. Torrey Bot. Club 25: 55. (1898)
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