Flora of North America species comparison

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Horkelia tridentata var. tridentata

Horkelia tridentata var. flavescens
Photo is of parent taxon

cluster horkelia, three tooth horkelia
Photo is of parent taxon

hairycup horkelia, pale horkelia, three tooth horkelia
Stems

decumbent to nearly erect, 1–4(–7) dm.

± decumbent, 0.5–2.5(–4.5) dm.
Inflorescences

composed of 1+ 5–40-flowered ± capitate glomerules, these sometimes expanding with age.

composed of usually 1 3–25-flowered ± corymbiform cluster.
Flowers

4–9 mm diam.;

hypanthium 2–3.5(–5) mm diam., interior glabrous;

petals linear to oblanceolate, (1.5–)2–3.5(–4.5) × 0.3–1 mm, usually ± equal to or longer than sepals, apex acute to obtuse;

filaments 0.5–1(–2) × 0.1–0.2 mm, anthers 0.2–0.3(–0.4) mm;

styles 1–2 mm.

6–10 mm diam.;

hypanthium 2.5–5 mm diam., interior pilose (except in some North Coast Ranges populations);

petals ± broadly oblanceolate, (1–)1.5–3(–4) × 0.5–1.5 mm, often shorter than sepals, apex obtuse to rounded or mucronate;

filaments 1–2 × 0.2–0.4(–0.8) mm, anthers 0.3–0.5 mm;

styles 1.5–2.5 mm.
Achenes

1.5–2 mm, lightly rugose.

2–2.5 mm, strongly rugose.
2n

= 28.

Horkelia tridentata var. tridentata

Horkelia tridentata var. flavescens
Phenology Flowering spring–summer. Flowering summer.
Habitat Open areas, primarily in sagebrush communities and conifer woodlands, mainly on granitic or volcanic soil Open areas, primarily in conifer woodlands, often on serpentine soil
Elevation 300–2500 m (1000–8200 ft) 700–2000 m (2300–6600 ft)
Distribution
from FNA
CA; OR
[BONAP county map]
from FNA
CA; OR
[BONAP county map]
Discussion

Variety tridentata occurs throughout the Cascade Mountains and Sierra Nevada of California, and barely extends into southern Oregon near Ashland, Josephine County, where the presence of distal cauline glands on some plants indicates possible introgression with Horkelia congesta. A specimen from Glendale, Oregon, (Jones s.n., POM) that was annotated and cited by D. D. Keck (1938) as H. congesta subsp. nemorosa is fully comparable to the Ashland material of var. tridentata; the apparent disjunction in Douglas County needs to be confirmed.

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

Variety flavescens occurs primarily in the mountains of northwestern California, from Mendocino to Siskiyou counties. A single collection is confirmed from Curry County, Oregon (Bear Camp Trail, Leach 4554, OSC); other collections from Curry and Josephine counties may be hybrids between this variety and Horkelia congesta var. nemorosa. A second cluster of populations occurs in central Plumas and adjacent Lassen counties, California, and historic collections are known from near Truckee on the border of Nevada and Placer counties, California. D. D. Keck (1938) suggested that this bicentric distribution may have resulted from the independent coalescence of the diagnostic characteristics of var. flavescens. The locality of a collection purportedly from Washoe County, Nevada (80 miles north of Reno, Brooks s.n., RENO) needs to be confirmed.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 9, p. 269. FNA vol. 9, p. 270.
Parent taxa Rosaceae > subfam. Rosoideae > tribe Potentilleae > Horkelia > sect. Tridentatae > Horkelia tridentata Rosaceae > subfam. Rosoideae > tribe Potentilleae > Horkelia > sect. Tridentatae > Horkelia tridentata
Sibling taxa
H. tridentata var. flavescens
H. tridentata var. tridentata
Synonyms Potentilla tilingii H. flavescens, H. tridentata subsp. flavescens, Potentilla tilingii var. flavescens
Name authority unknown (Rydberg) Ertter & Reveal: Novon 17: 320. (2007)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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