Ambrosia artemisiifolia

Ambrosia artemisiifolia
Photo by John R. Gwaltney Southeastern Flora.com
Scientific classification
Kingdom:	Plantae
Division:	Magnoliophyta - Flowering plants
Class:	Magnoliopsida – Dicotyledons
Order:	Asterales
Family:	Asteraceae ⁄ Compositae
Genus:	Ambrosia
Species:	A. artemisiifolia
Binomial name
Ambrosia artemisiifolia L.
Natural range of Ambrosia artemisiifolia from USDA NRCS Plants Database.

Common names: Common Ragweed

Taxonomic notes

Synonyms: A. artemisiifolia Linnaeus var. elatior (Linnaeus) Descourtils; A. artemisiifolia Linnaeus var. paniculata (Michaux) Blank; A. artemisiifolia Linnaeus var. artemisiifolia; A. elatior Linnaeus; A. monophylla (Walter) Rydberg; A. glandulosa Scheele

Description

Annual. Are rhizomatous, perennial herb with pubescent stems and usually freely branched. The leaves are opposite, the upper are alternate, linear, 1-4.5cm long, 0.5-3mm wide, entire, the base are attenuate, and pubescent on both surfaces. The petioles are obscured by decurrent blade tissues. The racemes are 3-20cm long. The involucres are 1.5-3mm long. The nutlets are black in color, are pubescent at the apex, obovoid in shape, turgid, and 1.6-2.1mm long. Flowers September to October. (Radford 1964).

Annual. Grows 0.2-2m tall, with a taproot. Has freely branched stems. The leaves are deeply bipinnately dissected with acute sinuses, the lower are opposite, the upper are alternate, 5-15cm long. The segments are mostly less than 1cm wide and are acute. The pistillate involucres are fascicled in upper leaf axils, obovoid in shape, pubescent to glabrate, 2.5-3.5mm long, 1.5-2.5mm in diameter, angulate, each with 5-6 rarely fewer, erect projections toward the apex. The staminate heads are 2-4mm broad, irregularly more or less 5-lobed, peduncles 1-6mm long. The nutlets are brown in color and 3-3.5mm long. Flowers August to frost. (Radford 1964).

Distribution

It is common throughout Florida (Wunderlin and Hansen 2003) and throughout the entire United States (Hall 2003). It has been found in open pine woods, mixed hardwoods, wet hammocks, and along dried up shores of ponds. It does well in a number of human disturbed areas including old fields, drainage ditches, pastures, roadsides, sandy vacant lots, railroad gravel, blackland prairie soil, camping areas, wet pastures, levees, drainage ditches, along edges of mixed forests, recently disturbed boggy areas, along canals, and agricultural fields. It thrives in dry sandy soils to wet, peaty soils in high intensity light in open areas.

Ecology

Habitat

It is found in disturbed sites (Wunderlin and Hansen 2003).

Associated species include Agalinis divaricata, pine, hickory; Euphorbia, Andropogon, Bidens, Paspalum urvillei, P. notatum, Eragrostis oxylepis, Eleusine indica, Digitaria sanguinalis, Cyperus surinamensis, Ambrosia artemisifolia, Strophostyles helvola, Solanum americanum, S. sisymbriifolium, Daubentonia drummondii, Sesbania exaltata, cabbage palmetto, Emilia fosbergii, Paspalum setaceum, Heterotheca subaxillaris, Boerhavia diffusa, Bothriochloa ischaemum; Croton capitatus and various grasses (FSU Herbarium).

Phenology

It flowers and fruits from summer to late fall (Wunderlin and Hansen 2003, FSU Herbarium).

Fire ecology

It can live where winter-burned annually and has been found in firelanes of annually-burned pinelands (FSU Herbarium).

References and notes

Florida State University Robert K. Godfrey Herbarium database. URL: http://herbarium.bio.fsu.edu. Last accessed: June 2014. Collectors: Loran C. Anderson, Tom Barnes, R. Barbezat, Sarah Beem, S. Bennett, Kurt E. Blum, Michael B. Brooks, R. C. Darby, Frank DiCecco, William B. Fox, Mary A. Garland, Robert K. Godfrey, Bruce Hansen, G. G. Hedgcock, Norlan C. Henderson, Brenda Herrig, C. Jackson, T. Kanno, Robert Kral, Gary R. Knight, Elmo Law, Martha Lee, S. W. Leonard, S. J. Lombardo, C. L. Lundell, Travis MacClendon, Karen MacClendon, Sidney McDaniel, Richard S. Mitchell, J. B. Morrill, John B. Nelson, R. A. Norris, H. Okazaki, Dan Pittillo, A. E. Radford, Lloyd H. Shinners, Cecil R. Slaughter, Bill Stangler, William R. Stimson, Amanda R. Travis, Charles S. Wallis, Keenan Windler, and Wendy Zomlefer. States and Counties: Alabama: Baldwin. Colorado: Jefferson. Florida: Brevard, Columbia, Dade, Escambia, Franklin, Indian River, Jackson, Jefferson, Leon, Liberty, Okaloosa, Pasco, Polk, Putnam, and Wakulla. Georgia: Colquitt, Decatur, Fulton, Grady, and Thomas. Illinois: Coles, Cook, and Lawrence. Iowa: Fremont. Louisiana: Ouachita. Kansas: Riley. Maryland: Baltimore. Mississippi: Harrison and Oktibbeha. Missouri: Cass, Greene, and Ray. North Carolina: Ashe, Chowan, Macon, Madison, and Wayne. Oklahoma: Ottawa. Pennsylvania: Huntingdon. South Carolina: Dorchester, Lexington, and Richland. Tennessee: Grundy and Polk. Texas: Dallas. Virginia: Giles, Montgomery, and Van Zandt. Other countries: Japan.

Hall, David W. Illustrated Plants of Florida and the Coastal Plain: based on the collections of Leland and Lucy Baltzell. 1993. A Maupin House Book. Gainesville. 74. Print.

Radford, Albert E., Harry E. Ahles, and C. Ritchie Bell. Manual of the Vascular Flora of the Carolinas. 1964, 1968. The University of North Carolina Press. 1016-1018. Print.

Wunderlin, Richard P. and Bruce F. Hansen. Guide to the Vascular Plants of Florida. Second edition. 2003. University Press of Florida: Gainesville/Tallahassee/Tampa/Boca Raton/Pensacola/Orlando/Miami/Jacksonville/Ft. Myers. 296. Print.