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Ambrosia cheiranthifolia

(Rio Grande Ragweed)

Overview

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Endangered

Threat status

Interesting Facts

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Common Names

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Common Names in English:

Rio Grande Ragweed, South Texas Ambrosia, South Texas Ragweed

Description

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Family Compositae

The largest family of flowering plants , the Compositae (Asteraceae), comprising about 1,100 genera and more than 20,000 species and characterized by many small flowers arranged in a head looking like a single flower and subtended by an involucre of bracts. A head may consist of both ray flowers and disk flowers, as in the sunflower, of disk flowers only, as in the burdock, or of ray flowers only, as in the dandelion.

Tribe Heliantheae

The Heliantheae are a tribe of closely related genera of the sunflower family that can be readily recognized due to the association of a receptacular bract or chaff scale with each disk floret in the head . The heads usually include bisexual , actinomorphic disk florets with tubular corollas that have 4 or 5 distal lobes and also peripheral zygomorphic female or sometimes sterile florets with strap-shaped corollas that have 3 or fewer distal teeth. However, the ray flowers are sometimes absent and the heads are then discoid , containing only bisexual florets with tubular corollas. The pappus is absent or more commonly ranges from scales to stiff bristles . -- Gerald Carr.

Genus Ambrosia

Annuals , perennials , or shrubs , 10-400+ cm (usually rhizomatous ). Stems erect , decumbent , or prostrate , branched. Leaves usually cauline; opposite ± throughout or opposite (proximal ) and alternate or mostly alternate; sessile or petiolate ; blades (or lobes ) deltate, elliptic , filiform , lanceolate, linear , obovate , ovate , or rhombic (and most intermediate shapes ), usually pinnately, sometimes palmately lobed , ultimate margins entire or toothed , faces hairy or glabrate , usually gland-dotted or stipitate-glandular . Heads discoid (unisexual , pistillate proximal to or intermixed with staminates , staminates usually in racemiform to spiciform arrays; rarely, single plants all or mostly staminate or pistillate). Pistillate heads: phyllaries 12-30(-80+) in 1-8+ series, outer (1-) 5-8 distinct or ± connate , herbaceous, the rest (sometimes interpreted as paleae) ± connate, usually with free tips forming tubercles , spines, or wings (the whole becoming a hard perigynium or "bur") ; florets 1(-5+), corollas 0. Staminate heads: involucres cup-shaped to saucer-shaped , 1.5-6+ mm diam.; phyllaries 5-16+ in ± 1 series, ± connate; receptacles ± flat or convex ; paleae spatulate to linear, membranous, sometimes villous , hirtellous, and/or gland-dotted or stipitate-glandular, sometimes none; florets 5-60+; corollas whitish or purplish, ± funnelform , lobes 5, erect or incurved ; staminal filaments connate, anthers distinct or weakly coherent. Cypselae (black) ± ovoid or fusiform , enclosed within globose to obovoid , pyramidal , pyriform , obconic, or fusiform, hard, smooth , tuberculate , spiny , or winged "burs"; pappi 0. x = 18.

Species 40+: tropical to subtropical and temperate New World, mostly North America, some established in Old World.[1]

Physical Description

Species Ambrosia cheiranthifolia

Perennials or subshrubs , 10-30+ cm (rhizomatous and/or soboli­ferous, colonial ). Stems erect . Leaves opposite (distal sometimes alternate) ; petioles 0; blades lanceolate or lance-elliptic to lance-oblong or oblanceolate , 20-50(-70+) × 8-12(-25+) mm, rarely ± pinnately lobed (lobes ± deltate), bases cuneate (then rounded ), margins entire or toothed , abaxial faces densely strigose (silvery gray), adaxial faces strigillose . Pistillate heads clustered (in axils), proximal to staminates ; florets 1(-2). Staminate heads: peduncles 1-4+ mm; involucres cup-shaped (sometimes with black nerve in each lobe), 3-4+ mm diam., strigillose; florets 8-18+. Burs: bodies ± pyriform to ± globose , 2-3+ mm, glabrous or strigose, spines (1-) 3-5+, scattered , stoutly conic, 0.4-0.8+ mm, tips straight (often each with black nerve). 2n = 72. [source]

Habit: Forb/herb

Flowers: Bloom Period: June, July, August, September, October, November.

Size/Age/Growth

Size: 24-36" tall.

Habitat

Seasonally wet clays or sands, scrublands; 10-30+ m [2].

Biology

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Reproduction

Duration: Perennial

Growth

Culture: Space 24-36" apart.

Sunlight: Sun Exposure: Full Sun .

Moisture: Drought Tolerance: High

Temperature: Cold Hardiness: 8b, 9a, 9b, 10a, 10b. (map)

Taxonomy

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Notes

Name Status: Accepted Name .

Comment: Data Providers: CONABIO, Govaerts World Compositae Checklist A-G, IPNI, Tropicos. GCC LSID: urn :lsid:compositae.org:names:02BBE739-A0BF-440B-85FB-1A31C4CDE603

Last scrutiny: 10-Aug-09

Similar Species

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Members of the genus Ambrosia

ZipcodeZoo has pages for 36 species, subspecies, varieties, forms, and cultivars in this genus:

A. acanthicarpa (Annual Bursage) · A. ambrosioides (Ambrosia Bursage) · A. artemisifolia (Common Ragweed) · A. artemisiifolia (Annual Bur-Sage Ambrosia Artemisiifolia) · A. artemisiifolia L. var. artemisiifolia L. (Ragweed) · A. artemisiifolia L. var. paniculata (Michx.) Blank. (Annual Ragweed) · A. artemisiifolia var. artemisiifolia (Common Ragweed) · A. artemisiifolia var. elatior (Annual Ragweed) · A. artemisiifolia var. paniculata (Annual Ragweed) · A. bidentata (Lance-Leaf Ragweed) · A. canescens (Hairy Ragweed) · A. chamissonis (Beach-Bur) · A. cheiranthifolia (Rio Grande Ragweed) · A. chenopodiifolia (San Diego Ambrosia) · A. confertiflora (Ragweed) · A. cordifolia (Heartleaf Bursage) · A. deltoidea (Rabbit Bush) · A. dumosa (Burro Bush) · A. elatior var. elatior (Ragweed) · A. eriocentra (Hollyleaf Bursage) · A. grayi (Bur Ragweed) · A. helenae (Helen Ragweed) · A. hispida (Coastal Ragweed) · A. ilicifolia (Holly-Leaf Bursage) · A. intergradiens (Intergrading Ragweed) · A. linearis (Linear-Leaf Bursage) · A. peruviana (Peruvian Ragweed) · A. psilostachya (Cuman Ragweed) · A. pumila (Dwarf Burr Ragweed) · A. tenuifolia (Field Ragweed) · A. tomentosa (Bur Sage Ragweed) · A. trifida (Blood Ragweed) · A. trifida var. texana (Texan Great Ragweed) · A. trifida var. trifida (Great Ragweed) · A. × helenae (Helen Ragweed) · A. × intergradiens (Intergrading Ragweed)

More Info

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Further Reading

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Notes

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Contributors

Data Sources

Accessed through GBIF Data Portal February 16, 2008:

Identifiers

Footnotes

  1. John L. Strother "Ambrosia". in Flora of North America Vol. 21 Page 3, 9, 10, 25. Oxford University Press. Online at EFloras.org. [back]
  2. "Ambrosia cheiranthifolia". in Flora of North America Vol. 21 Page 11, 17. Oxford University Press. Online at EFloras.org. [back]
Last Revised: 7/15/2012