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Jepson Interchange (more information)
©Copyright 1993 by the Regents of the University of California

  • Up-to-date information about California vascular plants is available from the Jepson eFlora.



David J. Keil, Family Editor and author, except as specified

Annual to tree
Leaves basal or cauline, alternate to whorled, simple to compound
Inflorescence: 1° inflorescence a head, each resembling a flower, 1–many, generally arrayed in cymes, generally subtended by ± calyx-like involucre; flowers 1–many per head
Flowers bisexual, unisexual, or sterile, ± small, of several types; calyx 0 or modified into pappus of bristles, scales, or awns, which is generally persistent in fruit; corolla radial or bilateral (rarely 0), lobes generally (0)4–5; stamens 4–5, anthers generally fused into cylinder around style, often appendaged at tips, bases, or both, filaments generally free, generally attached to corolla near throat; pistil 1, ovary inferior, 1-chambered, 1-seeded, style 1, branches 2, generally hair-tufted at tip, stigmas 2, generally on inside of style branches
Fruit: achene, cylindric to ovoid, generally deciduous with pappus attached
Genera in family: ± 1300 genera, 21,000 species (largest family of dicots): worldwide. Largest family in CA. Also see tribal key to CA genera: Strother 1997 Madroño 44(1):1–28. See glossary p. 25 for illustrations of general family characteristics.


Guy L. Nesom

Annual, biennial, perennial herb, fibrous-rooted, generally from short rhizome
Leaves oblanceolate to obovate or spoon-shaped, entire
Inflorescence: heads disciform or inconspicuously radiate, solitary or in few-headed clusters; buds erect; involucre hemispheric; phyllaries ± graduated, narrowly lanceolate outer and middle with 3 orange-resinous veins, at least near base; receptacle naked
Pistillate flowers in ± 2 series; outer generally with very narrow, sometimes coiled ligules; inner generally without ligules (except T. lonchophylla)
Disk flowers: corollas yellow, narrowly tubular, not hard or inflated; veins orange-resinous; style tips deltate
Fruit narrowly oblong, 2–4-ribbed, ± flat; pappus of barbed bristles in 1–2 series, outer 0 or bristles few, short, inner at maturity > involucre
Species in genus: ± 45 species: North America, Eurasia
Etymology: (Latin & Greek: 3 forms, from flower types)
Reference: [Nesom 1989 Phytologia 67:61–66]
Formerly treated as Erigeron sect. Trimorpha.


T. acris (L.) Gray var. debilis (A. Gray) G.L. Nesom


Biennial, perennial herb
Stems 10–35 cm, sparsely hairy, stalked-glandular
Leaves: basal 3–8 cm, gradually reduced upwards
Inflorescence wider near top or of only 1 head; phyllaries sparsely soft-hairy, stalked-glandular, greenish
Pistillate flowers in ± 2 series, outer with ligules 3–4.5 mm, inner without ligules
Disk flowers: corollas 4–5 mm
Fruits 2–2.4 mm
Ecology: Volcanic rocks, meadows
Elevation: 2700–2900 m.
Bioregional distribution: Cascade Range
Distribution outside California: to Alaska, Colorado
Synonyms: Erigeron d. (A. Gray) Rydb
Recent taxonomic note: Erigeron acris L. var. debilis A. Gray
See the CNPS Inventory for information about endangerment and rarity.
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bioregional map for TRIMORPHA%20acris%20var.%20debilis being generated

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