Flora of North America species comparison

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Horkelia tridentata var. tridentata
Photo is of parent taxon

cluster horkelia, three tooth horkelia
Stems

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

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

1.5–2 mm, lightly rugose.
2n

= 28.

Horkelia tridentata var. tridentata
Phenology Flowering spring–summer.
Habitat Open areas, primarily in sagebrush communities and conifer woodlands, mainly on granitic or volcanic soil
Elevation 300–2500 m (1000–8200 ft)
Distribution
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.)
Source FNA vol. 9, p. 269.
Parent taxa Rosaceae > subfam. Rosoideae > tribe Potentilleae > Horkelia > sect. Tridentatae > Horkelia tridentata
Sibling taxa
H. tridentata var. flavescens
Synonyms Potentilla tilingii
Name authority unknown
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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