Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Ageratum houstonianum
(Blue billygoatweed)

Toolbox

Datasheet

Ageratum houstonianum (Blue billygoatweed)

Summary

  • Last modified
  • 26 October 2018
  • Datasheet Type(s)
  • Invasive Species
  • Host Plant
  • Preferred Scientific Name
  • Ageratum houstonianum
  • Preferred Common Name
  • Blue billygoatweed
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Dicotyledonae
  • Summary of Invasiveness
  • A. houstonianum is an annual herb native to Mexico and Central America. It was brought to Europe shortly after its discovery, where its use as an ornamental started (...

Don't need the entire report?

Generate a print friendly version containing only the sections you need.

Generate report

Pictures

Top of page
PictureTitleCaptionCopyright
A. houstonianum; foliage and flowers.
TitleFoliage and flowers
CaptionA. houstonianum; foliage and flowers.
Copyright©Chris Parker/Bristol, UK
A. houstonianum; foliage and flowers.
Foliage and flowersA. houstonianum; foliage and flowers.©Chris Parker/Bristol, UK
Leaves of Ageratum conyzoides (a) and A. houstonianum (b).|Leaves of Ageratum conyzoides (a) and A. houstonianum (b). The leaves of A. conyzoides are opposite, 20-100 mm long, 5-50 mm wide, on hairy petioles 5-75 mm long, broadly ovate, with a rounded or narrowed acute base and an acute or obtuse or sometimes acuminate tip and toothed margins.
TitleLeaves
CaptionLeaves of Ageratum conyzoides (a) and A. houstonianum (b).|Leaves of Ageratum conyzoides (a) and A. houstonianum (b). The leaves of A. conyzoides are opposite, 20-100 mm long, 5-50 mm wide, on hairy petioles 5-75 mm long, broadly ovate, with a rounded or narrowed acute base and an acute or obtuse or sometimes acuminate tip and toothed margins.
Copyright©Chris Parker/Bristol, UK
Leaves of Ageratum conyzoides (a) and A. houstonianum (b).|Leaves of Ageratum conyzoides (a) and A. houstonianum (b). The leaves of A. conyzoides are opposite, 20-100 mm long, 5-50 mm wide, on hairy petioles 5-75 mm long, broadly ovate, with a rounded or narrowed acute base and an acute or obtuse or sometimes acuminate tip and toothed margins.
LeavesLeaves of Ageratum conyzoides (a) and A. houstonianum (b).|Leaves of Ageratum conyzoides (a) and A. houstonianum (b). The leaves of A. conyzoides are opposite, 20-100 mm long, 5-50 mm wide, on hairy petioles 5-75 mm long, broadly ovate, with a rounded or narrowed acute base and an acute or obtuse or sometimes acuminate tip and toothed margins.©Chris Parker/Bristol, UK
Inflorescences of Ageratum conyzoides (a) and A. houstonianum (b).|Inflorescences of Ageratum conyzoides (a) and A. houstonianum (b). Individual flower heads of A. conyzoides are light blue, white or violet, carried on 50-150 mm long peduncles, and are 5 mm across, 4-6 mm long with 60-75 tubular flowers. The flower head is surrounded by two or three rows of oblong bracts which are green with pale or reddish-violet tops.
TitleInflorescences
CaptionInflorescences of Ageratum conyzoides (a) and A. houstonianum (b).|Inflorescences of Ageratum conyzoides (a) and A. houstonianum (b). Individual flower heads of A. conyzoides are light blue, white or violet, carried on 50-150 mm long peduncles, and are 5 mm across, 4-6 mm long with 60-75 tubular flowers. The flower head is surrounded by two or three rows of oblong bracts which are green with pale or reddish-violet tops.
Copyright©Chris Parker/Bristol, UK
Inflorescences of Ageratum conyzoides (a) and A. houstonianum (b).|Inflorescences of Ageratum conyzoides (a) and A. houstonianum (b). Individual flower heads of A. conyzoides are light blue, white or violet, carried on 50-150 mm long peduncles, and are 5 mm across, 4-6 mm long with 60-75 tubular flowers. The flower head is surrounded by two or three rows of oblong bracts which are green with pale or reddish-violet tops.
InflorescencesInflorescences of Ageratum conyzoides (a) and A. houstonianum (b).|Inflorescences of Ageratum conyzoides (a) and A. houstonianum (b). Individual flower heads of A. conyzoides are light blue, white or violet, carried on 50-150 mm long peduncles, and are 5 mm across, 4-6 mm long with 60-75 tubular flowers. The flower head is surrounded by two or three rows of oblong bracts which are green with pale or reddish-violet tops. ©Chris Parker/Bristol, UK

Identity

Top of page

Preferred Scientific Name

  • Ageratum houstonianum Mill.

Preferred Common Name

  • Blue billygoatweed

Other Scientific Names

  • Ageratum mexicanum

International Common Names

  • English: Blue maudlin
  • French: Agerate bleu

Local Common Names

  • Cuba: celestina azul
  • Germany: Mexikanischer Leberbalsam
  • Japan: Murasakikakkoazami; Ookakkoazami

EPPO code

  • AGEHO (Ageratum houstonianum)

Summary of Invasiveness

Top of page

A. houstonianum is an annual herb native to Mexico and Central America. It was brought to Europe shortly after its discovery, where its use as an ornamental started (Johnson, 1971). The species is reported to be a weed and invasive outside its native range, due to its high production of small seeds with easy dispersal by wind or water (BioNet-EAFRINET, 2016). It is also dispersed by animals, clothing, vehicles, contaminated soils and agricultural produce (Johnson, 1971; BioNet-EAFRINET, 2016). Mainly as a garden escape, it has naturalized on farmlands, wastelands, roadsides, forest trails, crops, riverbanks and wetlands (BioNet-EAFRINET, 2016). The species is reported as invasive in China, Taiwan (PIER, 2016), Mozambique, Swaziland, Tanzania, Zimbabwe, USA (Hawaii), Cuba, Peru, Australia, Fiji, French Polynesia, New Zealand, and as a declared weed and alien invader plant with the highest category of invasiveness in South Africa (Oviedo Prieto et al., 2012; BioNet-EAFRINET, 2016; PIER, 2016; SANBI, 2016). It is also reported as invasive in Kenya, Malawi and Rwanda. Barua et al. (2013) report the species as an invasive which has affected ecosystems, causing the decline of native species in Assam, India. It can be particularly invasive along waterways and in riparian vegetation (Weeds of Australia, 2016).

Taxonomic Tree

Top of page
  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Dicotyledonae
  •                     Order: Asterales
  •                         Family: Asteraceae
  •                             Genus: Ageratum
  •                                 Species: Ageratum houstonianum

Notes on Taxonomy and Nomenclature

Top of page

Ageratum is a Linnaean name derived from the Greek a (not), and geras (old age), referring to the long-lasting nature of the flowers. The majority of species are native to the New World. A. houstonianum was first collected in 1731, at Veracruz, Mexico, and is now a popular garden plant. The cultivated varieties include tetraploids and hybrids (Johnson, 1971). The species epithet comes from the English botanist Dr William Houston who first collected A. houstonianum and sent seeds back to the UK.

Description

Top of page

The following description is from Johnson, 1971:

Annual, (2.5-)3-7(-9) dm tall; roots fibrous, adventitious at lower nodes if stem decumbent; stems simple or branched, especially above, erect or decumbent, reddish to green, glandular-villous to lanate above, hairs white to yellowish; leaves opposite, at times alternate above, ovate to deltoid, 2.4-8.6(-9.5) cm long, (1.7-)2.9-6.5(-8) cm wide, apex rounded or acute, base cordate to truncate, margin crenate or rarely dentate, more or less ciliate, upper surface dark green, pilose, hairs scattered or dense, especially over the veins, lower surface pale green, penninerved, densely pilose, especially over veins, to nearly glabrous; petioles 0.6-3.5 mm long, densely white pilose, especially on upper ones; inflorescences terminal, the 5-15 heads borne in tight or open cymose clusters on densely pilose-puberulent (at times glandular) bracteolate peduncles; involucres campanulate, bracts biseriate, narrowly lanceolate, (3.75-)4-5 mm high, outer ones 0.5-0.75(-0.95) mm wide, green or brownish, 2-ribbed, densely pilose to nearly glabrous, apex acuminate, glandular-ciliate, at times deep red, margin entire, herbaceous to scarious, glandular-ciliate especially above; corolla (2.15-) 2.5-3.5 mm long, funnelform, tube white, glandular to glabrous, throat blue, lilac, lavender, rarely white, the 5 lobes upright or spreading, acute, externally puberulous, pigmented as the throat; achenes 5-angled, black, (1.15-)1.5-1.75 mm long, scabrous on angles, carpopodium white, prominent; pappus of 5 free oblong, scarious scales (1.5-)2-3(-3.4) mm long, margin pectinate, apex setiferous, setae scabrous, at times the scales apically truncate and without setae, then scales 0.1-0.15 mm long. 

Plant Type

Top of page Annual
Herbaceous
Seed propagated

Distribution

Top of page

A. houstonianum is native to Mexico and Central America (Johnson, 1971). It has spread mostly as a garden escape and it is naturalized in North America, the Caribbean, Africa, Asia, Europe and Oceania (see Distribution Table for details).

Distribution Table

Top of page

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

ChinaPresentIntroduced Invasive PIER, 2016Grasslands, roadsides, slopes in valleys, 100-1500m. Also cultivated.
-AnhuiPresentIntroduced Invasive PIER, 2016
-FujianPresentIntroduced Invasive PIER, 2016
-GuangdongPresentIntroduced Invasive PIER, 2016
-GuangxiPresentIntroduced Invasive PIER, 2016
-GuizhouPresentIntroduced Invasive PIER, 2016
-HainanPresentIntroduced Invasive PIER, 2016
-HebeiPresentIntroduced Invasive PIER, 2016
-HeilongjiangPresentIntroducedMissouri Botanical Garden, 2016
-Hong KongPresentIntroduced Invasive Corlett, 1992; PIER, 2016
-JiangsuPresentIntroduced Invasive PIER, 2016
-ShandongPresentIntroduced Invasive PIER, 2016
-SichuanPresentIntroduced Invasive PIER, 2016
-YunnanPresentIntroduced Invasive PIER, 2016
-ZhejiangPresentIntroduced Invasive PIER, 2016
Georgia (Republic of)PresentIntroducedUSDA-ARS, 2016
IndiaPresentIntroduced1883Sharma, 1987Common weed of wastelands and fallow fields. Common, cultivated in gardens, moist and shaded situations and around settlements
-AssamPresentIntroduced Invasive Barua et al., 2013
IndonesiaPresentIntroducedPIER, 2016
-JavaPresentIntroduced1875Backer, 1938Reported as one of the naturalized American species collected by O. Kuntze in 1875
JapanPresentIntroducedJohnson, 1971; PIER, 2016Okinawa
MyanmarPresentIntroducedUSDA-ARS, 2016
PhilippinesPresentIntroducedJohnson, 1971; Missouri Botanical Garden, 2016Mountains
TaiwanWidespreadIntroduced Invasive PIER, 2016Common weed from low to middle elevations
ThailandPresentIntroducedPIER, 2016
VietnamPresentIntroducedJohnson, 1971Escaped from cultivation

Africa

CameroonPresentIntroducedUSDA-ARS, 2016
Congo Democratic RepublicPresentIntroducedUSDA-ARS, 2016
EgyptPresentIntroduced2004Shaltout, 2004Reported as a new record for the flora of Egypt
EthiopiaPresentIntroducedUSDA-ARS, 2016
GuineaPresentMissouri Botanical Garden, 2016Nzérékoré
KenyaPresentIntroduced Invasive USDA-ARS, 2016; Witt and Luke, 2017
MadagascarPresentIntroducedUSDA-ARS, 2016
MalawiPresentIntroduced Invasive USDA-ARS, 2016; Witt and Luke, 2017
MozambiquePresentIntroduced Invasive BioNET-EAFRINET, 2016
RwandaPresentIntroduced Invasive Witt and Luke, 2017
Saint HelenaPresentIntroducedCronk, 1989Weed of cultivation
South AfricaPresentIntroduced Invasive SANBI, 2016As a declared weed and an alien invader plant.
SudanPresentIntroducedUSDA-ARS, 2016
SwazilandPresentIntroduced Invasive BioNET-EAFRINET, 2016
TanzaniaPresentIntroduced Invasive BioNET-EAFRINET, 2016Arusha, Iringa, Tanga
ZambiaPresentIntroducedUSDA-ARS, 2016
ZimbabwePresentIntroduced Invasive Maroyi, 2006; BioNET-EAFRINET, 2016Widely grown as a border plant

North America

BermudaPresentIntroducedNakahara and Hilburn, 1989
CanadaPresent only in captivity/cultivationIntroduced Not invasive Oliver, 1973
MexicoWidespreadNativeMissouri Botanical Garden, 2016Type locality at Veracruz. Also at Chiapas, Colima, Guerrero, Hidalgo, Jalisco, Morelos, Nayarit, Nuevo León, Oaxaca, Puebla, Querétaro, Quintana Roo, Tabasco, Yucatán
USAPresentPresent based on regional distribution.
-AlabamaPresentIntroducedUSDA-ARS, 2016
-ConnecticutPresentIntroducedUSDA-ARS, 2016
-FloridaPresentIntroducedUSDA-ARS, 2016
-GeorgiaPresentIntroducedUSDA-ARS, 2016
-HawaiiPresentIntroduced1937 Invasive Wester and Juvik, 1983; PIER, 2016Big Island, Kauai, Maui and Oahu
-MassachusettsPresent, few occurrencesIntroduced1880 Not invasive Sorrie, 2005“Waif” (sporadically), no habitat given.
-New YorkPresent only in captivity/cultivationIntroducedGrier and Grier, 1929Cold Spring Harbor
-North CarolinaPresentIntroducedUSDA-ARS, 2016
-PennsylvaniaPresent only in captivity/cultivationIntroducedMoldenke, 1946Outdoor, cultivated and becoming weedy in cultivated grounds.
-South CarolinaPresentIntroducedUSDA-ARS, 2016
-TexasPresentIntroducedUSDA-ARS, 2016

Central America and Caribbean

BelizePresentNativeMissouri Botanical Garden, 2016Cayo
Costa RicaPresentMissouri Botanical Garden, 2016Guanacaste, Heredia, Limón, Puntarenas
CubaPresentIntroduced Invasive Robinson, 1913; Oviedo Prieto et al., 2012Reported as of one of the species of most concern, as a transformer and an invasive in other countries
Dominican RepublicPresentIntroducedTorres and Liogier, 1970In pastures, Loma del Puerto Pedro García, Puerto Plata Prov., 800 m on limestone. Roadside, La Cumbre, Altamira, 300 m
El SalvadorPresentNativeMissouri Botanical Garden, 2016San Salvador
GuatemalaPresentIntroduced Not invasive Missouri Botanical Garden, 2016Alta Verapaz, Baja Verapaz, Huehuetenango, Petén, San Marcos
HondurasPresentNativeMissouri Botanical Garden, 2016Comayagua, Copán, Cortés, Francisco Morazán, Yoro
JamaicaPresentIntroduced1888Robinson, 1913; Johnson, 1921; Missouri Botanical Garden, 2016
MartiniqueRobinson, 1913
NicaraguaPresentNativeMissouri Botanical Garden, 2016Chinandega
PanamaPresentNativeMissouri Botanical Garden, 2016Bocas del Toro, Canal Area, Chiriquí, Panamá, Amambay
Puerto RicoPresent only in captivity/cultivationIntroduced Not invasive Acevedo-Rodriguez and Strong, 2012

South America

BoliviaPresentIntroducedMissouri Botanical Garden, 2016La Paz, Santa Cruz
ColombiaPresentIntroducedMissouri Botanical Garden, 2016Nueva Granada, Antioquia, Medellín, Chocó, Meta, Nariño, Valle del Cauca
EcuadorPresentIntroducedMissouri Botanical Garden, 2016Azuay, Morona-Santiago, Tungurahua, La Libertad, La Paz
PeruPresentIntroduced Invasive PIER, 2016
SurinamePresent only in captivity/cultivationIntroduced Not invasive Funk et al., 2007Widely cultivated, possibly naturalized
VenezuelaPresentIntroducedMissouri Botanical Garden, 2016Aragua, Monagas, Distrito Federal, Lara, Mérida, Táchira

Europe

AustriaPresentIntroducedJohnson, 1971; NOBANIS, 2016In disturbed areas. Common Intentional introduction
BelgiumPresentIntroduced Not invasive DAISIE, 2016
Czech RepublicPresentIntroduced Not invasive DAISIE, 2016
DenmarkPresent, few occurrencesIntroduced Not invasive NOBANIS, 2016Rare, in urban areas. Seeds sold from catalogues in late 1800's. Intentional and unintentional introduction
EstoniaPresentIntroducedNOBANIS, 2016
FrancePresentIntroducedJohnson, 1971Escaped from cultivation
GermanyPresent only in captivity/cultivationIntroducedThoden et al., 2009Seeds and plants available at nurseries
HungaryPresentIntroduced Not invasive DAISIE, 2016
ItalyPresentIntroduced Not invasive DAISIE, 2016
NorwayPresent only under cover/indoorsIntroduced2003 Not invasive NOBANIS, 2016In Norway the plant is unable to reproduce and it is mostly confined to garden centres and greenhouses
PortugalPresentIntroduced Not invasive DAISIE, 2016
-AzoresPresentIntroduced Not invasive DAISIE, 2016
-MadeiraPresentIntroduced Not invasive DAISIE, 2016"Established"
Russian FederationPresent only in captivity/cultivationIntroduced Not invasive Komarov, 1968
SpainPresentIntroducedDAISIE, 2016"Established"
SwedenPresent, few occurrencesIntroduced1933 Not invasive NOBANIS, 2016Disturbed areas, rare. In Upland in 2002, no longer in Skåne
UKPresent, few occurrencesIntroduced Not invasive Miller, 1768; PFAF, 2016An occasional garden escape
UkrainePresentIntroducedDAISIE, 2016

Oceania

AustraliaPresentIntroduced Invasive PIER, 2016
-QueenslandPresentIntroduced Invasive PIER, 2016
FijiPresentIntroduced Invasive PIER, 2016Viti Levu Island. Also cultivated
French PolynesiaPresentIntroduced Invasive PIER, 2016Nuku Hiva Island, Raivavae. Also cultivated on Huahine and Tahiti Islands
New CaledoniaPresentIntroducedPIER, 2016Ile Grande Terre
New ZealandPresentIntroduced Invasive PIER, 2016Invasive in Raoul Island. Also cultivated
Papua New GuineaPresentIntroduced Invasive PIER, 2016

History of Introduction and Spread

Top of page

A. houstonianum seeds were sent by Dr. William Houston to England from Veracruz, Mexico, where he first collected the species. The species naturalized and became a weed in hotbeds in England prior to 1768. It was cultivated in Europe by 1822, and reported in Salzburg (Austria) by 1860 (Johnson, 1971). It is cited as introduced to India in the early nineteenth century and reported as occupying the niches of upland herbaceous species, including Ageratum conyzoides (Sahu, 1982; Barua et al., 2013). Johnson (1971) reports the species as escaping from gardens and becoming established in central Florida, Cuba, Jamaica, and Hawaii. He also reports the species having escaped from cultivation in Africa, China, India, France, Java, Okinawa (Japan), the Philippines, and North Vietnam. First reports of the species in the USA and the Caribbean are from the late 1800's as an ornamental and escaping from cultivation (Sorrie, 2005; Missouri Botanical Garden, 2016). Although Palmer (2004) cites it as recently introduced in Hawaii, Fosberg (1943) collected the species at Honolulu in 1937, reporting it as escaped from cultivation.

Introductions

Top of page
Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Austria 1861 Ornamental purposes (pathway cause) Yes Johnson (1971) Cultivated at Salzburg
Cuba 1900 Yes Robinson (1913) In tobacco field
Hawaii 1937 Ornamental purposes (pathway cause) Yes Fosberg (1943)
Jamaica 1888 Yes Johnson (1921) In disturbed area
Norway 2003 Ornamental purposes (pathway cause) No NOBANIS (2016) Unintentional; not reproducing
Sweden 1933 Ornamental purposes (pathway cause) Yes NOBANIS (2016) Intentional introduction, in disturbed areas, rare.
UK 1768 Breeding and propagation (pathway cause) Yes Miller (1768) Brought to England by Dr. William Houston. Reported as a weed in hotbeds

Risk of Introduction

Top of page

The worldwide use of this species as a flower bed plant and the ease with which its small seeds are easily transported by wind and water makes A. houstonianum of high risk of introduction into open areas mainly in temperate zones. It is reported as a naturalized garden escape in many countries and a good colonizer (Johnson, 1921; Johnson, 1971; BioNet-EAFRINET, 2016; PIER, 2016; Missouri Botanical Garden, 2016). Seeds can spread unintentionally by being carried by animals, in clothes, vehicles, produce or soil (BioNet-EAFRINET, 2016). It is listed as a declared weed and alien invader plant by the government of South Africa (SANBI, 2016). 

Habitat

Top of page

A. houstonianum is reported as growing in pastures, disturbed sites, crops, roadsides, savannas, openings in forests, humid areas and riparian zones; from sea level to 1300 m elevation (BioNet-EAFRINET, 2016; PIER, 2016). In Australia it is also reported from gardens, pastures, wetlands and waterways (Weeds of Australia, 2016). It has been in cultivation since being brought to England a few years after its discovery (Johnson, 1971; Cornell Garden-Based Learning, 2016).  

Habitat List

Top of page
CategorySub-CategoryHabitatPresenceStatus
Terrestrial
Terrestrial – ManagedCultivated / agricultural land Present, no further details Harmful (pest or invasive)
Cultivated / agricultural land Present, no further details Natural
Cultivated / agricultural land Present, no further details Productive/non-natural
Managed forests, plantations and orchards Present, no further details Natural
Managed forests, plantations and orchards Present, no further details Productive/non-natural
Disturbed areas Present, no further details Natural
Rail / roadsides Present, no further details Natural
Urban / peri-urban areas Present, no further details Natural
Urban / peri-urban areas Present, no further details Productive/non-natural
Terrestrial ‑ Natural / Semi-naturalNatural forests Present, no further details Natural
Natural grasslands Present, no further details Natural
Riverbanks Present, no further details Natural
Wetlands Present, no further details Natural

Hosts/Species Affected

Top of page

A. houstonianum is a common weed of sugarcane crops in Queensland (Weeds of Australia, 2016).

Host Plants and Other Plants Affected

Top of page
Plant nameFamilyContext
Nicotiana tabacum (tobacco)SolanaceaeMain

Biology and Ecology

Top of page

Genetics

Chromosome number is reported as n=10, 20 (Johnson, 1971).

Reproductive Biology

The species propagates by seeds and vegetatively by the prostrate portion of the stem (Barua et al., 2013). It can be reproduced from cuttings (Cornell Garden-Based Learning, 2016).

Physiology and Phenology

Flowering and fruiting occur all year long (Flora of China Editorial Committee, 2016). Optimal germination reported is between 6.0-7.0 pH; seeds will not germinate on more acidic soils (Shoemaker and Carlson, 1990).

Environmental Requirements

Wielgolaski (1966) report 8°C as the minimum temperature for the optimal growth of the species. Nursery websites report the plant does not tolerate frost, although some state that the plants might survive, but with reduced to no flowering. It is reported as unable to reproduce outside in Norway, most probably due to low temperatures (NOBANIS, 2016). A. houstonianum grows well in free draining soils, and in full sun to partial shade (Cornell Garden-Based Learning, 2016).  

Climate

Top of page
ClimateStatusDescriptionRemark
Af - Tropical rainforest climate Preferred > 60mm precipitation per month
Am - Tropical monsoon climate Preferred Tropical monsoon climate ( < 60mm precipitation driest month but > (100 - [total annual precipitation(mm}/25]))
Aw - Tropical wet and dry savanna climate Preferred < 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation{mm}/25])
BS - Steppe climate Tolerated > 430mm and < 860mm annual precipitation
BW - Desert climate Tolerated < 430mm annual precipitation
Cf - Warm temperate climate, wet all year Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year
Cs - Warm temperate climate with dry summer Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers
Cw - Warm temperate climate with dry winter Preferred Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)
Ds - Continental climate with dry summer Tolerated Continental climate with dry summer (Warm average temp. > 10°C, coldest month < 0°C, dry summers)

Latitude/Altitude Ranges

Top of page
Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)
62 44

Air Temperature

Top of page
Parameter Lower limit Upper limit
Absolute minimum temperature (ºC) -5

Rainfall

Top of page
ParameterLower limitUpper limitDescription
Mean annual rainfall4301500mm; lower/upper limits

Soil Tolerances

Top of page

Soil drainage

  • free

Soil reaction

  • acid
  • alkaline
  • neutral

Soil texture

  • heavy
  • light
  • medium

Natural enemies

Top of page
Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Frankliniella schultzei Herbivore Leaves/Stems not specific
Microcephalothrips abdominalis Herbivore Leaves/Stems not specific
Pythium mamillatum Pathogen Roots not specific
Trialeurodes vaporariorum Herbivore Leaves/Stems not specific

Notes on Natural Enemies

Top of page

The oomycote Pythium mamillatum [Globisporangium mamillatum], which causes root rot, is reported to parasitize A. houstonianum (Middleton, 1943).

The species is affected by Botrytis sp., spider mites, thrips, whiteflies, plant lice, fungus gnats, parasitic nematodes and powdery mildew. Excessive humidity can cause oedema, as reported by the Cornell Garden-Based Learning resources (2016) and plant nursery websites.

Means of Movement and Dispersal

Top of page

The plant reproduces by seed, and wind and water are the main means of dispersal for the small, light seeds of this and other species of Ageratum (Johnson, 1971; BioNet-EAFRINET, 2016). Seeds also attach easily to animals (BioNet-EAFRINET, 2016), and are reported as attaching to clothes, vehicles and to spread through contaminated agricultural produce. Plant spread by escaping from cultivation (Johnson, 1971; BioNet-EAFRINET, 2016).

The species has been introduced as an ornamental outside its native range (Johnson, 1971; BioNet-EAFRINET, 2016).

Pathway Causes

Top of page
CauseNotesLong DistanceLocalReferences
Breeding and propagationSold as a flower bed plant. Yes Yes
Crop productionCan spread in contaminated agricultural produce Yes Yes BioNET-EAFRINET, 2016
Cut flower tradeTaller varieties are used for cut flowers Yes Yes Cornell Garden-Based Learning, 2016
DisturbanceReported to be a colonizer in disturbed sites Yes Johnson, 1921
Escape from confinement or garden escapeCited as escaping from gardens and naturalizing in nearby areas. Yes PFAF, 2016
Garden waste disposalEstablishes itself easily in open soil where cultivated. Yes Johnson, 1971
HitchhikerCan attach to animals, vehicles, clothes. Yes Yes Johnson, 1971
Horticulture Yes Yes
Internet salesSeeds sold over the internet. Yes Yes
Nursery tradePlants sold for gardens. Yes
Ornamental purposesUsed as ornamental and for landscaping, sold at nurseries. Yes Thoden et al., 2009
Seed trade Yes Yes

Pathway Vectors

Top of page
VectorNotesLong DistanceLocalReferences
Clothing, footwear and possessionsSeeds attach easily to clothes. Yes Yes Johnson, 1971
Land vehicles Yes Cornell Garden-Based Learning, 2016
Soil, sand and gravelEstablishes easily in open soil in cultivated land. Yes Johnson, 1971
Water Yes Johnson, 1971
Wind Yes Johnson, 1971

Impact Summary

Top of page
CategoryImpact
Economic/livelihood Positive and negative
Environment (generally) Positive and negative
Human health Positive

Economic Impact

Top of page

A. houstonianum is one of the host plants of the Tobacco Streak Virus (TSV) and the Ageratum Latent Virus (ALV), transmitted by pollen of the species or by the thrips Frankliniella schultzei and Microcephalothrips abdominalis, causing crop losses around the world (Sharman et al., 2015). It is also a host plant for Ageratum Enation Virus (AEV) and the Radish Leaf Curl Virus (RaLV), transmitted by whiteflies (Bemisia sp.) and causing yellow vein disease in several crops and ornamentals (Srivastava et al., 2015).

Zebu cattle have been reported to suffer from intoxication by grazing on A. houstonianum; symptoms include acute internal haemorrhages and a sub-acute photodynamic dermatitis. The plant toxicosis has been so severe to even cause the death of cattle (Noa et al., 2004).

A. houstonianum is a very common weed of sugar cane crops in Queensland, and is also a weed of other cropping systems in the coastal areas of southern and central Queensland (Weeds of Australia, 2016).

Environmental Impact

Top of page

Impact on Habitats

Barua et al. (2013) report that the species can produce between 30,000 to 40,000 seedlings and 8-20 mature plants per m2 in Assam, India. The seeds germinate almost simultaneously, creating a dense ground cover and colonies, which have a smothering effect over other species. Weeds of Australia (2016) reports that A. houstonianum is one of only a few introduced species which can colonise undisturbed or relatively intact open forest vegetation. It also forms dense patches on coastal dunes and headlands in New South Wales.

Impact on Biodiversity

The dense ground cover and colonies of A. houstonianum can exclude the growth of other species, causing changes in the species composition and reducing species richness (Barua et al., 2013). BioNet-EAFRINET (2016) also suggests that A. houstonianum has allelopathic effects on the germination and growth of other species.

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Abundant in its native range
  • Pioneering in disturbed areas
  • Tolerant of shade
  • Fast growing
  • Gregarious
  • Has propagules that can remain viable for more than one year
  • Reproduces asexually
Impact outcomes
  • Ecosystem change/ habitat alteration
  • Monoculture formation
  • Negatively impacts agriculture
  • Negatively impacts animal health
  • Negatively impacts livelihoods
  • Reduced native biodiversity
  • Threat to/ loss of native species
Impact mechanisms
  • Competition - monopolizing resources
  • Competition - smothering
  • Pest and disease transmission
  • Hybridization
  • Rapid growth
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Highly likely to be transported internationally deliberately
  • Difficult to identify/detect in the field

Uses

Top of page

Economic Value

A. houstonianum has been cultivated as a flower garden plant since the early 1800's, and several varieties have been developed (Johnson, 1971). It is valued for providing the uncommon blue colour to gardens and landscapes (Cornell Garden-Based Learning, 2016). Its use as a garden plant is encouraged to attract butterflies and deter deer (Cornell Garden-Based Learning, 2016).

The species contains secondary metabolites that suppress the development of the juveniles of Meloidogyne hapla, a nematode that causes significant damage and crop losses in temperate zones (Thoden et al., 2009). Intercropping of A. houstonianum and other aromatic species in apple orchards had reduced the abundance of the pests Aphis citricola [A. spiraecola] and Lepidoptera, increasing the density of beneficial insects of Trichogrammatidae, Ichneumonidae and Braconidae (Song et al., 2013; 2014). It has fungicidal activity against Phytophthora infestans, reducing the disease severity in tomato crops (Goufo et al., 2010).

Chemicals that induce the premature metamorphosis and sterilization of some insect species were isolated from A. houstonianum and are marketed as Precocene I and Precocene II (Jacobson, 1982).

Social Benefit

The species is used in traditional medicine to treat skin infections and sore throats (Johnson, 1971; Andrade-Cetto, 2009). Leaves are applied to wounds to stop bleeding (Bodner and Gereau, 1988). Tennyson et al. (2012a) report that the species has a high antioxidant activity with potential cosmetic and medicinal uses.

Essential oils have antimicrobial and antifungicidal properties (Pandey et al, 1984; Menut et al., 1993; Njateng et al., 2010). The plant also shows acaricidal properties against the tick Rhipicephalus lunulatus (Pamo et al., 2005). Leaf extracts have adulticidal activities, oviposition deterrent properties and repellent properties against the mosquitoes Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus; all vectors of diseases that affect humans and domestic animals (Ravindran et al., 2012; Tennyson et al., 2012b, 2012c).

Environmental Services

Koi (2008) list A. houstonianum as one of the nectar sources for the butterfly Eumaeus atala, which is listed as rare and vulnerable in Florida, USA. 

Uses List

Top of page

Environmental

  • Soil conservation

General

  • Ornamental

Materials

  • Essential oils
  • Oils
  • Pesticide

Medicinal, pharmaceutical

  • Source of medicine/pharmaceutical
  • Veterinary

Ornamental

  • Cut flower
  • Potted plant
  • Seed trade

Similarities to Other Species/Conditions

Top of page

A. houstonianum is closely related to Ageratum conyzoides, as is evidenced from the similarities of habit, achenes, pappus, and corollas (Johnson,1971). Both species can be difficult to differentiate in the field and in herbarium collections (Sharma, 1987). Weeds of Australia (2016) lists the following distinguishing characters:

  • A. houstonianum has numerous sticky hairs on the bracts surrounding its flower-heads (i.e. the involucral bracts are glandular pubescent). Each of the tiny flowers (i.e. florets) which make up the flower-heads have two short and narrow projections (i.e. style branches) that are about 1-2 mm long. The bases of the flower-heads are relatively small (3-6 mm across)
  • A. conyzoides has only a few hairs on the bracts surrounding its flower-heads (i.e. the involucral bracts are glabrous or sparsely pubescent). Each of the tiny flowers (i.e. florets) which make up the flower-heads have two long and narrow projections (i.e. style branches) that are about 5 mm long. The bases of the flower-heads are relatively large (5-8 mm across).

The genus Ageratum is also closely related to Alomia. They can be differentiated by the lack of a pappus in Alomia (Johnson, 1971). In Australia, the similar native plant Vernonia (Cyanthillium cinereum) is distinguished at the seed stage by seeds being topped with about 20 relatively large bristles (Weeds of Australia, 2016).

Prevention and Control

Top of page

A. houstonianum is listed by the government of South Africa as a "Category 1 declared weed"; which is the strictest category, and prohibits its importation, propagation and establishment on any land or inland water surface (SANBI, 2016).

Chemical Control

The application of the herbicides dicamba and 2,4-D cause visible foliar injury and reduce flowering on A. houstonianum (Hatterman-Valenti and Mayland, 2005). The herbicide diphenamid, applied to the soil reduces the growth of the species (Adamson and Crossley, 1968). Chemical control is not advised when A. houstonianum is growing in crop fields; the use of a 20% salt solution is suggested instead (BioNet-EAFRINET, 2016).

Gaps in Knowledge/Research Needs

Top of page

More information is needed about the invasiveness status of the species in some of the countries where it is reported as a weed and invasive; especially on its effects on habitats and other species. 

References

Top of page

Acevedo-Rodríguez P, Strong MT, 2012. Catalogue of the Seed Plants of the West Indies. Smithsonian Contributions to Botany, 98:1192 pp. Washington DC, USA: Smithsonian Institution. http://botany.si.edu/Antilles/WestIndies/catalog.htm

Adamson RM, Crossley JH, 1968. Annual flower plant growth as affected by soil-incorporated herbicides. Weed Science, 16(1):60-2

Andrade-Cetto A, 2009. Ethnobotanical study of the medicinal plants from Tlanchinol, Hidalgo, México. Journal of Ethnopharmacology, 122(1):163-171. http://www.sciencedirect.com/science/journal/03788741

Ashish Srivastava, Susheel Kumar, Raj SK, 2015. Molecular characterization of a begomovirus and betasatellite causing yellow vein net disease of Ageratum houstonianum. Plant Disease, 99(5):627-631. http://apsjournals.apsnet.org/loi/pdis

Backer CA, 1938. A revision of Kuntze's types of new Javan species. Brittonia, 3(1):75-90

Barua IC, Deka J, Devi M, 2013. Invasive weeds and vegetation dynamics in Assam. In: The role of weed science in supporting food security by 2020. Proceedings of the 24th Asian-Pacific Weed Science Society Conference, Bandung, Indonesia, October 22-25, 2013 [ed. by Bakar, B. H.\Kurniadie, D.\Tjitrosoedirdjo, S.]. Bandung, Indonesia: Weed Science Society of Indonesia, 166-170

BioNET-EAFRINET, 2016. Invasive plants key and fact sheets. http://keys.lucidcentral.org/keys/v3/eafrinet/index.htm

Bodner CC, Gereau RE, 1988. A contribution of Bontoc ethnobotany. Economic Botany, 42(3):307-369

Corlett RT, 1992. The naturalized flora of Hong Kong: a comparison with Singapore. Journal of Biogeography, 19(4):421-430

Cornell Garden-Based Learning, 2016. Learn, Garden and Reflect with Cornell Garden-Based Learning. http://gardening.cce.cornell.edu/

Cronk QCB, 1989. The past and present vegetation of St Helena. Journal of Biogeography, 16:47-64

DAISIE, 2016. Delivering Alien Invasive Species Inventories for Europe. European Invasive Alien Species Gateway. www.europe-aliens.org/default.do

Flora of China Editorial Committee, 2016. Flora of China. St. Louis, Missouri and Cambridge, Massachusetts, USA: Missouri Botanical Garden and Harvard University Herbaria. http://www.efloras.org/flora_page.aspx?flora_id=2

Fosberg FR, 1943. Notes on plants of the Pacific Islands-III. Bulletin of the Torrey Botanical Club, 70(4):386-397

Funk V, Hollowell T, Berry P, Kelloff C, Alexander SN, 2007. Checklist of the plants of the Guiana Shield (Venezuela: Amazonas, Bolivar, Delta Amacuro; Guyana, Surinam, French Guiana). Contributions from the United States National Herbarium, 584 pp

Goufo P, Fontem DA, Ngnokam D, 2010. Evaluation of plant extracts for tomato late blight control in Cameroon. New Zealand Journal of Crop and Horticultural Science, 38(3):171-176

Grier CR, Grier NM, 1929. A list of plants growing under cultivation in the vicinity of Cold Spring Harbor, N.Y. The American Midland Naturalist, 11(8):389-434

Hatterman-Valenti H, Mayland P, 2005. Annual flower injury from sublethal rates of dicamba, 2,4-D, and premixed 2,4-D+mecoprop+dicamba. HortScience, 40(3):680-684

Jacobson M, 1982. Plants, insects, and man: their interrelationships. Economic Botany, 36(3):346-354

Johnson DS, 1921. Invasion of virgin soil in the Tropics. Botanical Gazette, 72(5):305-312

Johnson MF, 1971. A monograph of the genus Ageratum L. (Compositae-Eupatorieae). Annals Missouri Botanical Garden, 58:6-88

Koi S, 2008. Nectar sources for Eumaeus atala (Lepidoptera: Lycaenidae: Theclinae). Florida Entomologist, 91(1):118-120. http://www.fcla.edu/FlaEnt/

Komarov VL, 1968. Flora of the USSR, Volume 25, Compositae. Leningrad, USSR: Academiae Scientiarum

Maroyi A, 2006. Preliminary checklist of introduced and naturalized plants in Zimbabwe. Kirkia, 18(2):177-247

Menut C, Lamaty G, Zollo PHA, Kuiate JR, Bessière JM, 1993. Aromatic plants of tropical central Africa. Part X. Chemical composition of the essential oils of Ageratum houstonianum Mill. and Ageratum conyzoides L. from Cameroon. Flavour and Fragrance Journal, 8(1):1-4

Middleton JT, 1943. The taxonomy, host range and geographic distribution of the genus Pythium. Memoirs of the Torrey Botanical Club, 20:1-171

Miller P, 1768. Gardeners dictionary, 8th ed

Missouri Botanical Garden, 2016. Tropicos database. St. Louis, Missouri, USA: Missouri Botanical Garden. http://www.tropicos.org/

Moldenke HN, 1946. A contribution to our knowledge of the wild and cultivated flora of Pennsylvania. Amer. Midl. Nat. 1946. 35 (2). (289-399). [New York Botanical Garden, New York, N.Y.]

Nakahara S, Hilburn DJ, 1989. Annotated checklist of the whiteflies (Homoptera: Aleyrodidae) of Bermuda. Journal of the New York Entomological Society, 97(3):261-264

Nash DL, Williams LO, 1976. Flora of Guatemala. Vernonieae, Astereae, Inuleae, Heliantheae, Anthemideae, Cynareae, Mutisieae, Cichorieae, Eupatorieae, Helenieae, Senecioneae. Fieldiana: Botany, 24(12):613 pp

Njateng GSS, Kuiate JR, Gatsing D, Tamokou JD, Mouokeu RS, Kuete V, 2010. Antidermatophytic activity and dermal toxicity of essential oil from the leaves of Ageratum houstonianum (Asteraceae). Journal of Biological Sciences, 10(5):448-454. http://scialert.net/qredirect.php?doi=jbs.2010.448.454&linkid=pdf

Noa M, Sánchez LM, Durand R, 2004. Ageratum houstonianum toxicosis in Zebu cattle. Veterinary and Human Toxicology, 46(4):193-194

NOBANIS, 2016. North European and Baltic Network on Invasive Alien Species. http://www.NOBANIS.org

Oliver RW, 1973. Annual flowers for Canadian gardens. Ottawa, Canada: Plant Research Institute

Oviedo Prieto R, Herrera Oliver P, Caluff MG, et al. , 2012. National list of invasive and potentially invasive plants in the Republic of Cuba - 2011. (Lista nacional de especies de plantas invasoras y potencialmente invasoras en la República de Cuba - 2011). Bissea: Boletín sobre Conservación de Plantas del Jardín Botánico Nacional de Cuba, 6(Special Issue 1):22-96

Palmer CT, 2004. The inclusion of recently introduced plants in the Hawaiian ethnopharmacopoeia. Economic Botany, 58(1(Supplement 1)):S280-S293. http://rd.springer.com/article/10.1663/0013-0001%282004%2958%5BS280%3ATIORIP%5D2.0.CO%3B2

Pamo ET, Tendonkeng F, Kana JR, Payne VK, Boukila B, Lemoufouet J, Miegoue E, Nanda AS, 2005. A study of the acaricidal properties of an essential oil extracted from the leaves of Ageratum houstonianum. Veterinary Parasitology, 128(3/4):319-323. http://www.sciencedirect.com/science/journal/03044017

Pandey DK, Chandra H, Tripathi NN, Dixit SN, 1984. Mycotoxicity in leaves of some higher plants with special reference to that of Ageratum houstonianum Mill. Mykosen, 26:565-573

PFAF, 2016. Plants for a Future. http://www.pfaf.org/user/default.aspx

PIER, 2016. Pacific Island Ecosystems at Risk. Honolulu, USA: HEAR, University of Hawaii. http://www.hear.org/pier/index.html

Ravindran J, Samuel T, Alex E, William J, 2012. Adulticidal activity of Ageratum houstonianum Mill. (Asteraceae) leaf extracts against three vector mosquito species (Diptera: Culicidae). Asian Pacific Journal of Tropical Disease, 2(3):177-179. http://www.apjtcm.com

Robinson BL, 1913. Revisions of Alomia, Ageratum, and Oxylobus. Contributions from the Gray Herbarium of Harvard University, 42:438-491

Sahu TR, 1982. Taxonomic studies of the genus Ageratum L. in India. Feddes Repertorium, 93(1-2):61-65

SANBI, 2016. South African National Biodiversity Institute (SANBI). Declared weeds & alien invader plants. http://www.plantzafrica.com/miscell/aliens1.htm

Shaltout KH, 2004. An updated flora of Egypt. Diversity and Distributions, 10:75-79

Sharma VS, 1987. Comments on the identity of Ageratum conyzoides L., and A. houstonianum Mill. -two naturalized weeds in India. Feddes Repertorium, 98(11-12):557-560

Sharman M, Thomas JE, Persley DM, 2015. Natural host range, thrips and seed transmission of distinct Tobacco streak virus strains in Queensland, Australia. Annals of Applied Biology, 167(2):197-207. http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1744-7348

Shoemaker CA, Carlson WH, 1990. pH affects seed germination of eight bedding plant species. HortScience, 25(7):762-764

Song B, Jiao H, Tang G, Yao Y, 2014. Combining repellent and attractive aromatic plants to enhance biological control of three tortricid species (Lepidoptera: Tortricidae) in an apple orchard. The Florida Entomologist, 79(4):1679-1689

Song BeiZhou, Tang GuangBo, Sang XuSheng, Zhang Jie, Yao YunCong, Wiggins N, 2013. Intercropping with aromatic plants hindered the occurrence of Aphis citricola in an apple orchard system by shifting predator-prey abundances. Biocontrol Science and Technology, 23(4):381-395. http://www.tandfonline.com/doi/full/10.1080/09583157.2013.763904

Sorrie BA, 2005. Alien vascular plants in Massachusetts. Rhodora, 107(931):284-329

Tennyson S, Balaraju K, Park KyungSeok, Ravindran KJ, Eapen A, William SJ, 2012. In vitro antioxidant activity of Ageratum houstonianum Mill. (Asteraceae). Asian Pacific Journal of Tropical Disease, No.Supplement 2:S712-S714. http://www.apjtcm.com/zz/2012s2/32.pdf

Tennyson S, Ravindran J, Eapen A, William J, 2012. Repellent activity of Ageratum houstonianum Mill. (Asteraceae) leaf extracts against Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae). Asian Pacific Journal of Tropical Disease, 2(6):478-480. http://www.apjtcm.com/zz/20126/12.pdf

Tennyson S, Ravindran KJ, Eapen A, William SJ, 2012. Effect of Ageratum houstonianum Mill. (Asteraceae) leaf extracts on the oviposition activity of Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae). Parasitology Research, 111(6):2295-2299. http://rd.springer.com/article/10.1007/s00436-012-3083-7/fulltext.html

The Plant List, 2013. The Plant List: a working list of all plant species. Version 1.1. London, UK: Royal Botanic Gardens, Kew. http://www.theplantlist.org

Thoden TC, Hallmann J, Boppré M, 2009. Effects of plants containing pyrrolizidine alkaloids on the northern root-knot nematode Meloidogyne hapla. European Journal of Plant Pathology, 123(1):27-36. http://springerlink.metapress.com/link.asp?id=100265

Torres AM, Liogier AH, 1970. Chromosome numbers of Dominican Compositae. Brittonia, 22(3):240-245

USDA-ARS, 2016. Germplasm Resources Information Network (GRIN). National Plant Germplasm System. Online Database. Beltsville, Maryland, USA: National Germplasm Resources Laboratory. https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch.aspx

Weeds of Australia, 2016. Weeds of Australia, Biosecurity Queensland Edition. http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/search.html?zoom_query=

Wester L, Juvik JO, 1983. Roadside Plant-Communities on Mauna-Loa, Hawaii. Journal of Biogeography, 10(4):307-316

Wielgolaski FE, 1966. The influence of air temperature on plant growth and development during the period of maximal stem elongation. Oikos, 17(2):121-141

Witt, A., Luke, Q., 2017. Guide to the naturalized and invasive plants of Eastern Africa, [ed. by Witt, A., Luke, Q.]. Wallingford, UK: CABI.vi + 601 pp. http://www.cabi.org/cabebooks/ebook/20173158959 doi:10.1079/9781786392145.0000

Contributors

Top of page

26/05/2016 Original text by:

Jeanine Vélez-Gavilán, University of Puerto Rico at Mayagüez

Distribution Maps

Top of page
You can pan and zoom the map
Save map