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Daniel Potter & Barbara Ertter, family description, key to genera; treatment of genera by Daniel Potter, except as noted

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).
110 genera, ± 3000 species: worldwide, especially temperate; many cultivated for ornamental, fruit, especially Cotoneaster, Fragaria, Malus, Prunus, Pyracantha, Rosa, Rubus. [Potter et al. 2007 Plant Syst Evol 266:5–43] Number of teeth is per leaf or leaflet, not per side of leaf or leaflet, except in Drymocallis. —Scientific Editors: Daniel Potter, Thomas J. Rosatti.
Unabridged references: [Robertson 1974 J Arnold Arbor 55:303–332, 344–401, 611–662]

Key to Rosaceae


Barbara Ertter

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.
20 species: western North America. (J. Horkel, German plant physiologist, 1769–1846) [Ertter & Reveal 2007 Novon 17:315–325] Many attractive to bees; data apply to basal leaves, pressed hypanthia.

Key to Horkelia

H. californica Cham. & Schltdl.
Plant clumped, green. Stem: 10–120 cm. Leaf: stipules entire; leaflets ± separated, ± ovate to round, ± hairy. Inflorescence: open, of few to many separate flowers and few-flowered clusters; pedicels generally 1–20 mm. Flower: hypanthium width 4–10 mm, 1–2 × length, bractlets ± 4–6 mm, generally ± 2 mm wide, ovate, often toothed; sepals generally 4–6 mm; petals 3–8 mm, generally oblanceolate to elliptic; anthers 0.8–1.8 mm; pistils generally > 50. Fruit: ± 1 mm. Often confused with Drymocallis species (terminal leaflets distinct). Varieties intergrade. [Online Interchange]

H. californica var. frondosa (Greene) Ertter & Reveal
Leaf: 10–40 cm; sheathing base ± hairy; leaflets 3–5 per side, 15–60 mm, ± evenly double-toothed < 1/4 to base, generally unlobed; terminal leaflet 20–90 mm. Flower: hypanthium inner wall glabrous; sepals not red-mottled inside; filaments 1–2 mm, base 0.5–1.5 mm wide; style 2–3 mm.
Coastal scrub, canyons, poison-oak thickets; 10–400 m. Central Western California. [Horkelia californica subsp. frondosa (Greene) Ertter] May–Oct [Online Interchange]

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Citation for the whole project: Jepson Flora Project (eds.) 2013. Jepson eFlora,, accessed on Mar 29 2015
Citation for this treatment: [Author of taxon treatment] 2013. Horkelia, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on Mar 29 2015

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Geographic subdivisions indicated for the distribution of Horkelia californica var. frondosa Markers link to CCH specimen records. If the markers are obscured, reload the page [or change window size and reload]. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.
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.
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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.