Jepson Flora Project: Jepson Interchange    

link to manual TREATMENT FROM THE JEPSON MANUAL (1993) previous taxon | next taxon
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.



Willard W. Payne

Annual to shrub, monoecious
Leaves often opposite below, generally alternate above, generally petioled, hairy, glandular
Inflorescence: staminate heads generally many in ± spikes or racemes, phyllaries fused into shallow cup; pistillate heads generally clustered below staminate, generally spiny, bur-like; involucre ± 0; receptacle chaffy; chaff scales spirally arrayed, fused below, tips generally becoming spiny; each pistillate flower in separate chamber
Staminate flowers ± many; corolla yellow or translucent; anthers free; style unbranched
Pistillate flowers 1–5; corolla 0; style branches long
Fruit enclosed in bur; pappus 0
Etymology: (Greek: early name for aromatic plants; the mythic food of the gods)
[Payne 1976 Plant Syst Evol 125:169–178] Closely related to (indistinct from) Hymenoclea [Miao et al. 1995 Amer J Bot 82:924–932; Baldwin et al. 1996 Madroño 43:15–27] Wind-blown pollen often highly allergenic.


A. dumosa (A. Gray) Payne


Shrub 2–9 dm, much-branched
Stems softly gray-white canescent
Leaves generally ± clustered on short branches, (sub)sessile; blade 0.5–4 cm, ± ovate, 1–3-pinnate, canescent
Inflorescence: staminate heads 3–5 mm diam, involucre lobes 5–8; pistillate heads 2-flowered
Fruit: bur 5–9 mm, spheric, golden to purple or brown, puberulent; spines 12–35, scattered, straight, flat, sharp
Chromosomes: 2n=36,72,108,126,144
Ecology: Creosote-bush scrub
Elevation: < 1600 m.
Bioregional distribution: East of Sierra Nevada, Desert
Distribution outside California: to sw Utah, Arizona, nw Mexico
Flowering time: Feb–Jun, Sep–Nov
Synonyms: Franseria d. A. Gray
Hybridizes with Hymenoclea salsola
Horticultural information: TRY.

previous taxon | next taxon
bioregional map for AMBROSIA%20dumosa being generated
N.B. The distribution depicted here differs from that given in The Jepson Manual (1993)

Retrieve Jepson Interchange Index to Plant Names entry for Ambrosia dumosa
Retrieve dichotomous key for Ambrosia
Retrieve multiple-entry key (MEKA) for Ambrosia
Overlay Consortium of California Herbaria specimen data by county on this map
Show other taxa with the same California distribution | Read about bioregions | Get lists of plants in a bioregion
Return to the Jepson Interchange main page
Return to treatment index page

University & Jepson Herbaria Home Page |
General Information | University Herbarium | Jepson Herbarium |
Visiting the Herbaria | On-line Resources | Research |
Education | Related Sites
Copyright © by the Regents of the University of California