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Erigeron bonariensis
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Asterids
Order:	Asterales
Family:	Asteraceae
Genus:	Erigeron
Species:	E. bonariensis
Binomial name
	Erigeron bonariensis; L.
	Occurrence data from GBIF
Synonyms
	Synonymy Erigeron bonariense L. ; Conyza bonariensis (L.) Cronquist ; Leptilon bonariense (L.) Small ; Marsea bonariensis (L.) V.M. Badillo ; Aster ambiguus (DC.) E.H.L.Krause ; Conyza ambigua DC. ; Conyza chenopodioides DC. ; Conyza crispa] (Pourret) Rupr. ; Conyza crispa (Pourr.) Cout. ; Conyza gracilis Hoffmanns. & Link ; Conyza hispida Kunth ; Conyza ivifolia Burm.f. 1768 ; Conyza ivifolia (L.) Less. 1831 ; Conyza leucodasys Miq. ; Conyza linearis DC. ; Conyza linifolia (Willd.) Täckh. 1956 not L. 1753 ; Conyza plebeja Phil. ; Conyza rufescens Hoffmanns. & Link ; Conyza sinuata Elliott ; Conyza sordescens Cabrera ; Conyzella linifolia (Willd.) Greene ; Dimorphanthes ambigua C.Presl ; Dimorphanthes angustifolia Cass. ; Dimorphanthes crispa Rupr. ; Dimorphanthes hispida (Kunth) Cass. ; Dimorphanthes linifolia (Willd.) Rupr. ; Erigeron ambiguus (DC.) Sch.Bip. 1845 not Nutt. 1818 ; Erigeron canadensis Ten. 1831 not L. 1753 ; Erigeron contortus Desf. ex Pers1 ; Erigeron coranopifolius Willk. & Lange ; Erigeron crispus Pourr. ; Erigeron gusalakensis Rech.f. & Edelb. ; Erigeron linearifolius Cav ; Erigeron linifolius Willd. ; Erigeron looseri Herter ; Erigeron naudinii (Bonnet) Bonnier ; Erigeron sordidus Gillies ex Hook. & Arn. ; Erigeron transsilvanicus Schur ; Erigeron undulatus Moench ; Eschenbachia ambigua Moris ; Eupatorium dictyophyllum DC. ; Leptilon linifolium (Willd.) Small ; Pulicaria gracilis (Hoffmanns. & Link) Nyman ; Pulicaria rufescens (Hoffmanns. & Link) Nyman ;

Erigeron bonariensis is a species in the family Asteraceae, found throughout the tropics and subtropics as a pioneer plant; its precise origin is unknown, but most likely it stems from Central America or South America. It has become naturalized in many other regions, including North America, Europe and Australia.

Common names of E. bonariensis include flax-leaf fleabane, wavy-leaf fleabane, Argentine fleabane, hairy horseweed, asthma weed and hairy fleabane.^[2]

Description

Erigeron bonariensis grows up to 75 cm (29.5 in) in height and its leaves are covered with stiff hairs, including long hairs near the apex of the bracts. Its flower heads have white ray florets and yellow disc florets. It can easily be confused with Erigeron canadensis, which grows taller, and E. sumatrensis.^[3]

It flowers in August and continues fruiting until the first frosts. It is instantly recognisable by its blue-green foliage, very narrow, undulate stem-leaves, and purple-tipped involucral bracts. It reproduces only by seed, which are easily blown and spread by wind.^{[citation needed]}

Distribution and habitat

Erigeron bonariensis is found throughout the tropics and subtropics as a pioneer plant; its precise origin is unknown, but most likely it stems from Central America or South America. It has become naturalized in many other regions, including North America, Europe and Australia.^[4]^[5]^[6]^[7]

E. bonariensis is a rare alien in southeastern England, found along walls and in cracks in pavements and concrete driveways.^{[citation needed]} It is widespread throughout Australia, where it thrives on roadsides, fallows, pastures, gardens, lawns, footpaths, parks, riparian vegetation, forest and wetland perimeters, waste dumps and disturbed grounds.^[8]^[9]

Photographic Description

Dry Summer Form

The following are bright dry summer 1st-year forms; in contrast to shady damp winter forms that follow.

General view
Top-heavy greyish gangly look with initial central inflorescence subsequently overtopped by some side ones
Broad heads (may be narrower especially in winter) usually with reddened tips
Head close up
Leaf narrow showing hairs
Leaf surface hairs (similar underside), sometimes poorly hairy
Hairs at leaf tip
Leaf base hairs (a few long ones usually present) and underside hairs
Stem leaves of robust stems multi-lengthed, grey (sometimes green)

Winter, Damp, Shady, Biennial Forms

Showing diffusely branched or strangled appearances with small flower heads

Winter form near water in the open
Strangled winter form in the open
Winter form in damp shade
From a biennial form
May have particularly reddened heads

Other photos

Erigeron bonariensis growing as a weed on a building in New Delhi, India
Stiff hairs cover the plant.
Basal rosette leaves, before plant matures and flowers, Maui, Hawaii
Foliage becomes grey-green in dry-summer regions, such as Israel
White ray flowers and yellow disc flowers in fully "open" flower heads, Maui, Hawaii
Flower heads are followed by seeds, which are easily carried by the wind.