Jepson eFlora: Taxon page
Vascular Plants of California
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Horkelia tridentata var. tridentata

Higher Taxonomy
Family: RosaceaeView DescriptionDichotomous Key
Common Name: ROSE FAMILY
Habit: Annual to tree, glandular or not. Leaf: simple to palmately or pinnately compound, generally alternate; stipules free to fused (0), persistent to deciduous. Inflorescence: cyme, raceme, panicle, cluster, or flowers 1; bractlets on pedicel ("pedicel bractlets") generally 0--3(many), subtended by bract or generally not. Flower: generally bisexual, radial; hypanthium free or fused to ovary, saucer- to funnel-shaped, subtending bractlets ("hypanthium bractlets") 0--5, alternate sepals; sepals generally 5; petals generally 5, free; stamens (0,1)5--many, anther pollen sacs generally 2; pistils (0)1--many, simple or compound, ovary superior to inferior, styles 1--5. Fruit: 1--many per flower, achene (fleshy-coated or not), follicle, drupe, or pome with generally papery core, occasionally drupe-like with 1--5 stones. Seed: generally 1--5 (per fruit, not per flower).
Genera In Family: 110 genera, +- 3000 species: worldwide, especially temperate; many cultivated for ornamental, fruit, especially Cotoneaster, Fragaria, Malus, Prunus, Pyracantha, Rosa, Rubus. Note: Number of teeth is per leaf or leaflet, not per side of leaf or leaflet, except in Drymocallis.
eFlora Treatment Author: Daniel Potter & Barbara Ertter, family description, key to genera, treatment of genera by Daniel Potter, except as noted
Scientific Editor: Daniel Potter, Thomas J. Rosatti.
Genus: HorkeliaView DescriptionDichotomous Key

Habit: Perennial herb, generally +- glandular, generally resinous-smelling; caudex generally branched. Stem: generally ascending to erect. Leaf: generally basal, odd-1-pinnately compound, generally +- flat; cauline alternate, reduced upward; leaflets 2--15 per side, uppermost lateral generally +- fused with terminal. Inflorescence: cyme; pedicels generally straight, bractlets 0. Flower: hypanthium cup-like, +- flat-bottomed, width +- 2 × length, bractlets 5, generally 2/3 sepals; sepals often reflexed; petals generally +- = sepal, blunt, white; stamens 10, filaments +- flat, often forming a tube; pistils 2--many, ovary superior, style attached below fruit tip, +- thicker at base. Fruit: achene.
Species In Genus: 20 species: western North America. Etymology: (J. Horkel, German plant physiologist, 1769--1846) Note: Many attractive to bees; data apply to basal leaves, pressed hypanthia.
eFlora Treatment Author: Barbara Ertter
Reference: Ertter & Reveal 2007 Novon 17:315--325
Species: Horkelia tridentataView Description 

Habit: Plant rosetted or tufted, +- gray, +- odorless; caudex 0--few-branched. Stem: < 45 cm, +- glabrous to sparsely glandular above. Leaf: 3--12 cm; stipules entire to forked; leaflets 2--5 per side, separated, 5--30 mm, generally elliptic to oblong, +- 3-toothed < 1/4 to base (entire), at least lower surface +- densely hairy. Inflorescence: clusters +- head-like, generally 3--40-flowered; pedicels generally 1--6 mm. Flower: hypanthium width 1--2 × length, bractlets < 0.5 mm wide, linear; sepals generally 1.5--3 mm; petals 1.5--4 mm; filament base generally +- 0.2--0.5 mm wide, anthers 0.2--0.5 mm; pistils 5--15, style 1--2.5 mm.
Note: Varieties intergrade extensively.
Horkelia tridentata Torr. var. tridentata
Stem: decumbent to +- erect. Inflorescence: clusters 1--many. Flower: 4--7 mm wide; hypanthium generally 2--3.5 mm wide, inner wall generally glabrous; petals generally >= sepals, generally narrow-oblanceolate; filaments generally 0.5--1 mm. Fruit: 1.5--2 mm. Chromosomes: n=14.
Ecology: Granitic or volcanic soils; Elevation: 300--2500 m. Bioregional Distribution: e KR, CaR, SN, MP; Distribution Outside California: southern Oregon. Flowering Time: Apr--Aug
Synonyms: Horkelia tridentata subsp. tridentata
Jepson eFlora Author: Barbara Ertter
Reference: Ertter & Reveal 2007 Novon 17:315--325
Index of California Plant Names (ICPN; linked via the Jepson Online Interchange)

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Citation for this treatment: Barbara Ertter 2012, Horkelia tridentata var. tridentata, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on August 04, 2021.

Citation for the whole project: Jepson Flora Project (eds.) 2021, Jepson eFlora,, accessed on August 04, 2021.

Horkelia tridentata var. tridentata
click for enlargement
© 2009 Barry Breckling
Horkelia tridentata var. tridentata
click for enlargement
© 2016 Steve Matson
Horkelia tridentata var. tridentata
click for enlargement
© 2009 Barry Breckling
Horkelia tridentata var. tridentata
click for enlargement
© 2009 Barry Breckling
Horkelia tridentata var. tridentata
click for enlargement
© 2015 Neal Kramer
Horkelia tridentata var. tridentata
click for enlargement
© 2016 Steve Matson

More photos of Horkelia tridentata var. tridentata in CalPhotos

Geographic subdivisions for Horkelia tridentata var. tridentata:
e KR, CaR, SN, MP
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map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).


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Data provided by the participants of the  Consortium of California Herbaria.
View all CCH records
All markers link to CCH specimen records. The original determination is shown in the popup window.
Blue markers indicate specimens that map to one of the expected Jepson geographic subdivisions (see left map). Purple markers indicate specimens collected from a garden, greenhouse, or other non-wild location.
Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.

CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa, if there are more than 1 infraspecific taxon in CA.
Blue line denotes eFlora flowering time (fruiting time in some monocot genera).