Ambrosia L.

Ambrosia, as currently understood (see Strother 2006), is a genus of ca. 40 species. All are native in temperate to tropical regions of the New World, mostly in North America. Several species are noxious weeds of agricultural land.

The shape and dimensions of the involucre of female capitula (bur) at maturity provide a good character for the separation of the Belgian representatives of Ambrosia. Female capitula are much less numerous than male capitula and are usually found in the axils of the leaves or bracts at the base of the male inflorescence.

Excellent microscopic photos of leaf and fruit details for all taxa treated in this account are provided by Amor Morales & al. (2012).

1 Most leaves 3-5-lobed, the uppermost sometimes subentire, usually all opposite. Stem usually 100-200 (-400) cm. Involucre of female capitula (bur) 5-10 mm long at maturity === 3. Ambrosia trifida

1 All leaves pinnately divided (nearly to base), the uppermost alternate. Stem up to 100 cm. Involucre of female capitula 3-6 mm at maturity === 2

2 Annual. Involucre of female capitula at maturity with (3-) 5-7 spines (0,5-1 mm long) === 1. A. artemisiifolia

2 Perennial. Involucre of female capitula at maturity without spines, at most with tubercules ca. 0,1-0,5 mm long === 2. A. psilostachya



Amor Morales Á., Navarro Andrés F. & Sánchez Anta Mª.Á. (2012) Datos corológicos y morfológicos de las especies del género "Ambrosia" L. ("Compositae") presentes en la Península Ibérica. Botanica Complutensis 36: 85-96. [available online at:]

Gudzinskas Z. (1993) Genus Ambrosia L. (Asteraceae) in Lithuania. Thaiszia 3: 89-96.

Lambinon J., Delvosalle L., Duvigneaud J. (avec coll. Geerinck D., Lebeau J., Schumacker R. & Vannerom H. (2004) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Cinquième édition. Jardin botanique national de Belgique, Meise: CXXX + 1167 p.

Lawalrée A. (1947) Les Ambrosia adventices en Europe occidentale. Bull. Jard. Bot. État Bruxelles 18: 305-315.

Lawalrée A. (1953) Note complémentaire sur les Ambrosia adventices en Europe occidentale. Bull. Soc. Roy. Bot. Belg. 87: 207-208.

Martin M.D., Quiroz-Claros E., Brush G.S. & Zimmer E.A. (2018) Herbarium collection-based phylogenetics of the ragweeds (Ambrosia, Asteraceae). Molecular phylogenetics and evolution 120: 335-341. 

Miao B., Turner B.L. & Simpson B. & Mabry T.J. (1995) Chloroplast DNA study of the generaAmbrosia s.l. andHymenoclea (Asteraceae): Systematic implications. Pl. Syst. Evol. 194: 241-255.

Miao B., Turner B.L. & Mabry T.J. (1995) Systematics Implications of Chloroplast DNA Variation in the Subtribe Ambrosiinae (Asteraceae: Heliantheae). Am. J. Bot. 82: 924-932.

Payne W.W. (1964) A re-evaluation of the genus Ambrosia (Compositae). Journ. Arnold Arbor. 45(4): 401-430.

Payne W.W. (1966) Notes on the ragweeds of South America with the description of two new species: Ambrosia pannosa and A. parvifolia (Compositae). Brittonia 18: 28-37.

Rich T.C.G. (1994) Ragweeds (Ambrosia L.) in Britain. Grana 33: 38-43.

Sluschny H. (2008) Zur Verbreitung der Ambrosia-Arten in Mecklenburg-Vorpommern. Botanischer Rundbrief für Mecklenburg-Vorpommern 43: 57-68.

Strother J.L. (2006) Ambrosia. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 21. Oxford University Press, New York-Oxford: 10-18.

Wagner W.H. Jr. (1959) An annotated bibliography of ragweed (Ambrosia). Rev. Allergy Appl. Immunol. 13: 353-403.

Taxonomic name: 
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith