Ambrosia bidentata Michx.
  Dicotyledoneae   Asteraceae   Ambrosia

Ambrosia bidentata, leaf and flower
© Kay Yatskievych, 2003 · 1
Ambrosia bidentata, leaf and flower

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FamilyScientific name @ source (records)
Endosphaeraceae  Rhodochytrium spilanthis @ BPI (1)
Entylomataceae  Entyloma polysporum @ BPI (2)
Erysiphaceae  Erysiphe cichoracearum @ BPI (3)

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Ambrosia bidentata  Michx.

Lanceleaf Ragweed

Ambrosia bidentata plant

Family - Asteraceae

Habit - Taprooted annual.

Stems - Ascending to erect, to 1 m, roughened-pubescent with mixed hairs, some of these with pustular bases, sometimes glabrous near the base, often somewhat shiny.

Ambrosia bidentata stem Stem.

Leaves - Mostly alternate (the lowermost occasionally opposite), sessile. Leaf blades 1-7 cm long, 0.4-1.0 cm wide, lanceolate, unlobed or with a pair of small lobes toward the base, the lobes triangular, the margins otherwise entire, the surfaces sparsely to moderately roughened-pubescent with short, loosely ascending, pustular-based hairs and stiff, longer hairs (mostly along the midvein), the upper surface sometimes only sparsely hairy, the undersurface often with small, sessile glands (slightly sticky to the touch), not or only slightly paler than the upper surface.

Inflorescence - Staminate heads sessile in relatively dense, solitary spikes, the staminate involucre 2.5-4.0 mm wide, with 3 lobes, the lateral ones small, the terminal lobe elongate, the outer surface with minute, sessile glands, the terminal lobe with a patch of relatively long, stiff hairs. Pistillate heads in small axillary clusters, the involucre enclosing 1 floret and with 1 stout, conical beak, 5-8 mm long at fruiting, more or less ovoid, with usually 4 longitudinal angles or ridges, each terminating in a short spine, moderately hairy.

Ambrosia bidentata inflorescence Inflorescence.

Flowers - Staminate heads with 10-150 disc florets, the stamens with the filaments fused into a tube, the anthers free but adjacent to one another in a ring, the corolla 2-4 mm long, narrowly bell-shaped, white to pale yellow, sometimes purplish-tinged toward the tip, usually minutely hairy and often also glandular. Pistillate heads with 1 or 2 florets, the corolla absent. Pappus absent.

Ambrosia bidentata flowers Flowers.

Fruits - Fruits 3.0-4.5 mm long, globose to ovoid, grayish tan to nearly black, glabrous, completely enclosed in the persistent pistillate involucre and dispersed as an intact bur.

Flowering - July - October.

Habitat - Prairies, fields, waste ground, pond margins, pastures, roadsides, railroads.

Origin - Native to U.S.

Other info. - This weedy species is common throughout most of Missouri except for the northwest corner of the state. Its natural range is centered in the Missouri-Arkansas region and extends to a few adjoining states. The plant is easy to identify in the field because of the sharply pointed basal lobes present on many of the leaves, and its single terminal spike of staminate flowers. Like the other species in this genus, this plant is a cause of hay fever in the fall.

Photographs taken off Hwy 60, Carter County, MO., 8-31-03, and at Big Spring, MO., 8-3-04.

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Ambrosia bidentata Michx.
lanceleaf ragweed

Image of Ambrosia bidentata

General Information
Symbol: AMBI2
Group: Dicot
Family: Asteraceae
Duration: Annual
Growth Habit : Forb/herb
Native Status : L48   N
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Native Status:
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Steve Hurst. Provided by ARS Systematic Botany and Mycology Laboratory . United States, MD. Usage Requirements .

Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York. Vol. 3: 341. Provided by Kentucky Native Plant Society . Scanned by Omnitek Inc . Usage Requirements .




Click on a scientific name below to expand it in the PLANTS Classification Report.
Rank Scientific Name and Common Name
Kingdom Plantae – Plants
Subkingdom Tracheobionta – Vascular plants
Superdivision Spermatophyta – Seed plants
Division Magnoliophyta – Flowering plants
Class Magnoliopsida – Dicotyledons
Subclass Asteridae
Order Asterales
Family Asteraceae ⁄ Compositae – Aster family
Genus Ambrosia L. – ragweed
Species Ambrosia bidentata Michx. – lanceleaf ragweed

Subordinate Taxa

This plant has no children

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FNA Vol. 21 Page 11, 15 Login | eFloras Home | Help
FNA | Family List | FNA Vol. 21 | Asteraceae | Ambrosia

11. Ambrosia bidentata Michaux, Fl. Bor.-Amer. 2: 182. 1803.

Annuals, 10—30(—100+) cm. Stems erect. Leaves mostly opposite; petioles 0—0.5 mm; blades ± lanceolate to lance-linear, 15—40+ × 3—6(—10+) mm, bases rounded to cordate, margins entire or with (1—)2(—4) basal lobes, abaxial and adaxial faces ± piloso-hispid and gland-dotted. Pistillate heads clustered, proximal to staminates; florets 1. Staminate heads: peduncles 0—0.5 mm; involucres obliquely cup-shaped (lateral lobe longer than others), 2.5—4 mm diam., piloso-hispid; florets 6—8+. Burs: bodies pyramidal, 5—8 mm, piloso-hispid, spines 4(—5), ± distal, ± acerose, 0.5—1 mm, tips straight.

Flowering Jul—Oct. Dry, disturbed sites; 200—500 m; Ala., Ark., Conn., D.C., Ga., Ill., Ind., Iowa, Kans., Ky., La., Md., Minn., Miss., Mo., N.C., Ohio, Okla., Tenn., Tex., Va., W.Va.

Hybrids between Ambrosia bidentata and A. trifida have been recorded.

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Number of matches : 3
Query: SELECT * FROM img WHERE ready=1 and taxon like "Ambrosia bidentata%" and (lifeform != "specimen_tag" OR lifeform != "Plant") ORDER BY taxon

Click on the thumbnail to see an enlargement

Ambrosia bidentata
Ambrosia bidentata
Lanceleaf Ragweed
ID: 0000 0000 0214 0037 [detail]
© 2014 Richard Spellenberg

Ambrosia bidentata
Ambrosia bidentata
Lanceleaf Ragweed
ID: 0000 0000 0214 0038 [detail]
© 2014 Richard Spellenberg

Ambrosia bidentata
Ambrosia bidentata
Lanceleaf Ragweed
ID: 0000 0000 0214 0039 [detail]
© 2014 Richard Spellenberg

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