Sonchus asper
(spiny sow-thistle)

Pictures

Picture	Title	Caption	Copyright
Title Habit Caption Sonchus asper (spiny sow-thistle); habit, showing flower and apical part of plant. East Sussex, UK. April 2017. Copyright ©Emőke Dénes/via wikipedia - CC BY-SA 4.0	Habit	Sonchus asper (spiny sow-thistle); habit, showing flower and apical part of plant. East Sussex, UK. April 2017.	©Emőke Dénes/via wikipedia - CC BY-SA 4.0
Title Habit Caption Sonchus asper (spiny sow-thistle); habit. Australia. May 2014. Copyright ©Harry Rose (Macleay Grass Man)/via flickr - CC BY 2.0	Habit	Sonchus asper (spiny sow-thistle); habit. Australia. May 2014.	©Harry Rose (Macleay Grass Man)/via flickr - CC BY 2.0
Title Habit Caption Sonchus asper (spiny sow-thistle); habit. Australia. May 2014. Copyright ©Harry Rose (Macleay Grass Man)/via flickr - CC BY 2.0	Habit	Sonchus asper (spiny sow-thistle); habit. Australia. May 2014.	©Harry Rose (Macleay Grass Man)/via flickr - CC BY 2.0
Title Basal rosette Caption Sonchus asper (spiny sow-thistle); rosette, with developing leaves. Maui, Hawaii, USA. May 2015. Copyright ©Forest & Kim Starr - CC BY 4.0	Basal rosette	Sonchus asper (spiny sow-thistle); rosette, with developing leaves. Maui, Hawaii, USA. May 2015.	©Forest & Kim Starr - CC BY 4.0

Identity

Preferred Scientific Name

• Sonchus asper (L.) Hill

Preferred Common Name

• spiny sow-thistle

Other Scientific Names

• Sonchus aemulus Merino
• Sonchus asper (L.) Vill.
• Sonchus asper All.
• Sonchus borderi Gand.
• Sonchus carolinianus Walter
• Sonchus cuspidatus Blume
• Sonchus decipiens (De Not.) Zenari
• Sonchus eryngiifolius Sosn.
• Sonchus eryngioides DC.
• Sonchus fallax Wallr.
• Sonchus glaber Thunb.
• Sonchus infestus Poepp. ex DC.
• Sonchus spinosus Lam.
• Sonchus spinulosus Bigelow
• Sonchus sulphureus Boiss.
• Sonchus tibesticus Quézel
• Sonchus umbellatus E.Mey. ex DC.
• Sonchus viridis Zenari

International Common Names

• English: blue sow-thistle; prickly sow-thistle; rough sow-thistle; spiny-leaf sow-thistle
• Spanish: cardo; cardo espinoso; cerraja
• French: chaudronnet; laiteron âpre; laiteron épineux; laiteron piquant; laiteron rude; lastron piquant
• Chinese: hua ye dian ku cai
• Portuguese: serralha áspera; serralha espinhosa; serralha preta

Local Common Names

• Czech Republic: mlé
• Dominican Republic: lechuguilla; yerba espinosa
• Finland: aitoukonhattu; metsätähti
• Norway: skogstjerne; venusvogn
• Sweden: balkansippa; skogsalpsklocka; skogsstjärna; trädgårdsstormhatt

Summary of Invasiveness

Sonchus asper is an annual herb considered native to Europe, Africa and Asia that has been introduced to a wide range of countries around the world, where it frequently becomes an environmental and agricultural weed. The species grows in a wide range of habitats and climates, and produces large numbers of seeds (>20,000 seeds), which are easily dispersed by wind and water, but also as contaminants. Because S. asper is very successful colonising disturbed sites, as well as natural habitats at early successional stages, it has the potential to outcompete native plant species, inhibit the establishment of other native pioneer species and thus alter natural successional processes. It is also regarded as a noxious species due to hosting diseases and pests that affect crops.

Taxonomic Tree

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Asterales
•                         Family: Asteraceae
•                             Genus: Sonchus
•                                 Species: Sonchus asper

Notes on Taxonomy and Nomenclature

Sonchus is a genus of about 60-90 species that contains annual, biennial and perennial herbs. Its main diversity occurs in Africa, the Mediterranean region and the mid-Atlantic archipelagos, but it also comprises woody species endemic to Macaronesia, and several cosmopolitan weedy species (Kim et al., 2007; Flora of China Editorial Committee, 2018).

Description

This description was taken from the Flora of China Editorial Committee (2018):

Herbs 20-50 cm tall, annual or occasionally biennial. Stem usually unbranched and glabrous below synflorescence. Basal and lower stem leaves extremely variable, obovate, spatulate, or elliptic, 7-13 × 2-5 cm, undivided or ± irregularly pinnatisect, glabrous, adaxially dark green and ± glossy, base attenuate and ± auriculate, margin usually densely spinulosely dentate, apex acute, acuminate, or obtuse; lateral lobes ± triangular, semiorbicular, or elliptic. Middle and upper stem leaves spatulate to lanceolate, base auriculately clasping with conspicuous rounded and appressed auricles, otherwise similar to lower leaves. Synflorescence densely corymbiform, with few capitula. Capitula with many florets; peduncle 0.5-5 cm, slender, glabrous or densely glandular hairy. Involucre ± campanulate, 1.2 cm. Phyllaries abaxially glabrous or more rarely glandular hairy, apex acute; outer phyllaries narrowly lanceolate, 1-2 mm wide. Corolla 1 cm. Achene ± broadly obcolumnar, 2-3 mm, strongly compressed, ± winged, between lateral ribs usually with 3 slender ribs on either side, space between slender ribs much wider than ribs, smooth with only lateral ribs usually antrorsely finely spinulose. Pappus 7 mm ± caduceus.

Plant Type

Distribution

The native distribution range of S. asper is still uncertain, but the species is considered native to Europe, Africa and temperate Asia. It has been introduced and become naturalized across parts of Asia, Scandinavia, Canada, USA, Mexico, Central and South America, the Caribbean, southern Africa, Australia, New Zealand, the Pacific Region and some sub-Antarctic islands, such as Gough Island, Auckland Islands and Campbell Island (DAISIE, 2018; Flora Mesoamericana, 2018; GISD, 2018; PIER, 2018; USDA-ARS, 2018).

Distribution Table

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.

History of Introduction and Spread

Like many Old World weeds, S. asper was apparently introduced unintentionally into the New World by European explorers during the colonisation of America. In North America, it was probably introduced early in the 1800s. Achenes of S. asper have been found in adobe bricks used to build missions in California. In Canada, the earliest herbarium collection is from 1871, in Ontario (Hutchinson et al., 1984).

Risk of Introduction

No economic uses are known for S. asper, making the risk of intentional introductions low. However, this cosmopolitan weed is a prolific seed producer and its tiny seeds can be easily dispersed by human activities, as a contaminant in crop and grass seed, a hitchhiker on footwear, or attached to animals, which increases the risk of spread (Hutchinson et al., 1984; GISD, 2018; PROTA, 2018).

Habitat

S. asper is a pioneer species that often invades sites disturbed by human activities, such as roadsides, cultivated fields, wastelands, gardens, gravel pits, mines and logged areas. It also occurs in areas naturally disturbed by grazing, landslides or fire. It can also be found in mountain slopes, forest and field margins, ruderal areas, grasslands, along lakeshores and streams, and on muddy sites, at elevations from 750 m to 3700 m (Flora Mesoamericana, 2018; Flora of China Editorial Committee, 2018; Flora of North America Editorial Committee, 2018; PROTA, 2018). Across Canada and the USA, this species is fairly common in riparian and coastal habitats, particularly on disturbed sites (Hutchinson et al., 1984; ANHP, 2010; GISD, 2018).

Habitat List

Hosts/Species Affected

S. asper has been listed as a weed of alfalfa, cotton, coffee, beans, garbanzo beans, tomato and maize plantations (Villaseñor and Espinosa, 1998; Vibrans, 2009).

Host Plants and Other Plants Affected

Growth Stages

Biology and Ecology

Genetics

The chromosome number reported for S. asper is 2n = 18 (Hutchinson et al., 1984; Flora of China Editorial Committee, 2018). Crossings between S. asper and S. oleraceus may occur, but the hybrids are sterile (Flora of North America Editorial Committee, 2018).

Reproductive Biology

S. asper has bisexual self-compatible flowers. Flowers are pollinated by insects, including solitary bees and flies, but also by wind. Seeds are produced both through selfing and outcrossing (Hutchinson et al., 1984).

Physiology and Phenology

In North America, seeds of S. asper germinate from spring through fall. Seeds normally germinate 2-3 weeks after planting. The seedlings attain the rosette stage at 6 weeks of age and start producing flowers after 9 weeks. Mature achenes are produced about a week after flowering (Hutchinson et al., 1984). Plants that germinate in the fall overwinter as rosettes (Hutchinson et al., 1984; Flora of North America Editorial Committee, 2018).

In China, S. asper has been recorded flowering and fruiting from May to October (Flora of China Editorial Committee, 2018). In the USA, it produces flowers and fruits from March to November in the north and year-round in the south (Flora of North America Editorial Committee, 2018). In Central America, it has been recorded with flowers and fruits throughout the year (Flora Mesoamericana, 2018; Flora of Nicaragua, 2018).

Longevity

S. asper is an annual or biennial herb (Flora of North America Editorial Committee, 2018; USDA-NRSC, 2018). It overwinters in the vegetative phase as rosettes or seeds. Seeds may remain viable in the soil for 1 to 3 years (Hutchinson et al., 1984; DiTomaso and Healy, 2007).

Environmental Requirements

The cosmopolitan range of S. asper suggests a broad tolerance of climatic variation and great ability to thrive in many different environments. However, light and disturbance seem to be the major requirements for the germination and establishment of this species. Currently, S. asper grows mostly in disturbed sites extending from 70°N to 50°S, in areas with annual rainfall ranging form 300 mm to 3000 mm and daily temperature above 5°C. It can grow in clay, loam and sandy soils with pH between 6.5 and 9. Plants tolerate saline soils and calcium carbonate content up to 55% (Hutchinson et al., 1984; Holm et al., 1997; ANHP, 2010).

Climate

Latitude/Altitude Ranges

Air Temperature

Rainfall

Rainfall Regime

Soil Tolerances

Soil drainage

• free

Soil reaction

• alkaline
• neutral

Soil texture

• heavy
• light
• medium

Special soil tolerances

• saline

Natural enemies

Notes on Natural Enemies

S. asper is an important alternative host of a number of crop pests and diseases, including (Hutchinson et al. 1984; Vieira and Barreto, 2006; GISD, 2018):

• aphids (Aphididae) Aphis fabae, Hyperomyzus lactucae, H. pallidus and Uroleucon sonchi;

• the larva of the Cecidomyiid fly Aphidoletes aphidimyza, which was originally described from S. asper in Europe;

• leaf miners Ophiomyia pulicaria, O. coniceps, Phytomyza syngenesiae [Chromatomyia syngenesiae], Phytoliriomyza arctica and Calycomyza sonchi;

• the moth (Tortricidae) Cnephasia longana;

• nematodes Meloidogyne spp. and Pratylenchus penetrans;

• fungal infections Bremia lactucae (downy mildew), Sphaerotheca fuliginea [Podosphaera fuliginea] (a powdery mildew) and Alternaria sonchi; 

• viruses: beet western yellows virus, lettuce necrotic yellows virus, beet yellow stunt virus and sowthistle yellow vein virus.

Means of Movement and Dispersal

Natural Dispersal

S. asper spreads by seed. Each reproductive plant may produce between 20,000 and 26,000 seeds that are primarily dispersed by wind, but also by water, or spread after being ingested by birds or small mammals. Seeds remain viable after passing through the digestive system of birds, small mammals and livestock (Hutchinson et al. 1984; DiTomaso and Healy, 2007; ANHP, 2010; GISD, 2018).

Accidental Introduction

Seeds of S. asper may be dispersed by animals, adhered to feathers and fur, and also by humans on clothing, shoes, vehicles and machinery. The species has also been documented as a contaminant of commercial grass and crop seeds (Hutchinson et al. 1984; DiTomaso and Healy, 2007; ANHP, 2010; GISD, 2018).

Pathway Causes

Pathway Vectors

Economic Impact

S. asper is a weed of agricultural lands (Villaseñor and Espinosa, 1998; Vibrans, 2009), but is also an important alternative host of pests, viruses and diseases that affect crops. It acts as host to economically important aphids that are vectors of “yellows” virus diseases and it is also an important host of the downy mildew Bremia lactucae, one of the worst diseases affecting lettuce plantations (Hutchinson et al., 1984; Vieira and Barreto, 2006; GISD, 2018; PROTA, 2018). The species causes major problems in winter crops and tillage systems throughout southern Australia, Southeast Queensland and Northern New South Wales (Weeds of Australia, 2018).

Environmental Impact

S. asper is an environmental weed very successful at colonising disturbed and open sites. There, it can occur scattered, but also forming dense stands that outcompete native plant species and inhibit the establishment of other native pioneer species, thus causing alterations in natural successional processes. Because S. asper is pollinated by insects, its introduction can also alter plant-pollinator interactions (Hutchinson et al., 1984; ANHP, 2010; GISD, 2018; Weeds of Australia, 2018).

Risk and Impact Factors

• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Highly adaptable to different environments
• Is a habitat generalist
• Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
• Pioneering in disturbed areas
• Highly mobile locally
• Benefits from human association (i.e. it is a human commensal)
• Fast growing
• Has high reproductive potential
• Gregarious
• Has propagules that can remain viable for more than one year

• Ecosystem change/ habitat alteration
• Modification of successional patterns
• Monoculture formation
• Negatively impacts agriculture
• Reduced native biodiversity
• Threat to/ loss of native species

• Competition - monopolizing resources
• Competition - smothering
• Pest and disease transmission
• Hybridization
• Rapid growth
• Produces spines, thorns or burrs

• Highly likely to be transported internationally accidentally
• Difficult to identify/detect as a commodity contaminant
• Difficult to identify/detect in the field
• Difficult/costly to control

Uses

S. asper is harvested from the wild for local use as food and medicine. The leaves are eaten as a cooked vegetable or occasionally raw in salads. In the Mediterranean region and Southeast Asia, use of S. asper as a vegetable is widespread. In Africa, its use as a vegetable is reported from Madagascar.

In Asia, the plant is pounded and applied as a poultice to wounds and boils (Useful Tropical Plants, 2014). In Africa, the plant is used to treat warts (PROTA, 2018).

Uses List

Human food and beverage

• Vegetable

Medicinal, pharmaceutical

• Traditional/folklore

Similarities to Other Species/Conditions

S. asper looks very similar to the close relative S. oleraceus, a species that is also a cosmopolitan weed. However, S. oleraceus has flatter, less spiky leaf margins and sharply acute, downward pointing auricles in leaves and bracts. In addition, in S. oleraceus, the achenes are narrower, never winged at the margins, transversely rugulose and scabrous at maturity. Most of them are brown, but those of the outermost whorl are paler and more olive in colour (Hutchinson et al., 1984; ANHP, 2010).

Prevention and Control

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Control                     

Physical/mechanical control

Small or isolated populations of S. asper can be manually removed while plants are young, prior to seed set. The taproot must be removed, as resprouting can occur if left in the soil.

Grazing of S. asper by cattle and sheep could be used to suppress infestations in pastures (GISD, 2018).

Biological control

In Australia, surveys searching for biological control agents of S. asper have identified the rust fungus Miyagia pseudosphaeria and an unidentified eriophyid mite species as potential candidates. However, studies determining the impact of these potential control agents on related native Australian species are still in progress (CSIRO, 2007; GISD, 2018).

Chemical control

Herbicides such as soxaben, 2,4-Dichlorophenoxyacetic acid, clopyralid, dicamba, glyphosate, picloram, Dimethyl tetrachloroterephthalate (DCPA), diethatyl-ethyl, MCPA, amitrole, atrazine, bromoxynil, chlorsulfuron, dichlorprop, isoxaben, norflurazon, oryzalin, oxyfluorfen and paraquat have been used to control infestations of S. asper in agricultural lands. However, S. asper has developed resistance to chlorsulfuron, atrazine and the herbicide metsulfuron-methyl (Rashid et al., 2003; GISD, 2018; Weeds of Australia, 2018). Biotypes resistant to the herbicides thifensulfuron, metsulfuron, prosulfuron, imazamox and imazethapyr have been found across North America, Australia and Europe (Park et al., 2012).

References

Acevedo-Rodríguez P, Strong MT, 2012. Catalogue of seed plants of the West Indies. Smithsonian Contributions to Botany, 98. Washington DC, USA: Smithsonian Institution.1192 pp.

ANHP, 2010. Alaska Natural Heritage Program. Datasheet for spiny sowthistle. Alaska, USA: University of Alaska Anchorage. http://accs.uaa.alaska.edu/files/invasive-species/Sonchus_asper_BIO_SOAS.pdf

Broome R, Sabir K, Carrington S, 2007. Plants of the Eastern Caribbean. Online database. Barbados: University of the West Indies. http://ecflora.cavehill.uwi.edu/index.html

CSIRO, 2007. Management and control of sowthistles in Australia. Wembley, WA, Australia: Commonwealth Scientific and Industrial Research Organisation.

DAISIE, 2018. Delivering Alien Invasive Species Inventories for Europe. DAISIE (online). http://www.europe-aliens.org/default.do

Danton P, Perrier C, Martinez RG, 2006. New catalogue of the vascular flora of the Juan Fernández Archipelago (Chile). (Nuevo catálogo de la flora vascular del Archipélago Juan Fernández (Chile)). Acta Botanica Gallica, 153(4), 399-587.

DiTomaso, J. M., Healy, E. A., 2007. Weeds of California and other Western States. Vol 1. In: Weeds of California and other Western States. Vol 1 . California, USA: UC Davis.1808 pp.

Flora Mesoamericana, 2018. Flora Mesoamericana. St. Louis, Missouri, USA: Missouri Botanical Garden. http://www.tropicos.org/Project/fm

Flora of China Editorial Committee, 2018. 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

Flora of Nicaragua, 2018. Flora of Nicaragua, Tropicos website. St. Louis, Missouri, USA: Missouri Botanical Garden. http://www.tropicos.org/ProjectList.aspx

Flora of North America Editorial Committee, 2018. Flora of North America North of Mexico. St. Louis, Missouri and Cambridge, Massachusetts, USA: Missouri Botanical Garden and Harvard University Herbaria. http://www.efloras.org/flora_page.aspx?flora_id=1

Florence J, Chevillotte H, Ollier C, Meyer JY, 2013. Botanical database of the Nadeaud Herbarium of French Polynesia. (Base de données botaniques Nadeaud de l'Herbier de la Polynésie Française). http://www.herbier-tahiti.pf

Fonseca, C. R., Guadagnin, D. L., Emer, C., Masciadri, S., Germain, P., Martin Zalba, S., 2013. Invasive alien plants in the Pampas grasslands: a tri-national cooperation challenge. Biological Invasions, 15(8), 1751-1763. http://rd.springer.com/article/10.1007/s10530-013-0406-2 doi: 10.1007/s10530-013-0406-2

GISD, 2018. Global Invasive Species Database (GISD). http://www.iucngisd.org/gisd/

Holm, L., Doll, J., Holm, E., Pancho, J., Herberger, J., 1997. World weeds: natural histories and distribution, New York, USA: John Wiley and Sons.xv + 1129 pp.

Hutchinson, I., Colosi, J., Lewin, R. A., 1984. The biology of Canadian weeds. 63. Sonchus asper (L.) Hill and S. oleraceus L. Canadian Journal of Plant Science, 64(3), 731-744.

IABIN, 2017. Invasives Information Network (I3N). Inter-American Biodiversity Information Network. http://www.institutohorus.org.br/iabin/i3n/

Khanna, K. K., 2009. Invasive alien angiosperms of Uttar Pradesh. Biological Forum, 1(2), 34-39. http://www.researchtrend.net

Kim SC, Chunghee L, Mejías JA, 2007. Phylogenetic analysis of chloroplast DNA matK gene and ITS of nrDNA sequences reveals polyphyly of the genus Sonchus and new relationships among the subtribe Sonchinae (Asteraceae: Cichorieae). Molecular Phylogenetics and Evolution, 44(2), 578-597.

Mir C, 2012. [English title not available]. (Estrategia Nacional de especies exóticas invasoras realizado en el marco del Proyecto “Mitigando las amenazas de las especies exóticas invasoras en el Caribe Insular”). Dominican Republic: Ministerio de Medio Ambiente y Recursos Naturales Santo Domingo.

Nayak, S. K., Satapathy, K. B., 2015. Diversity, uses and origin of invasive alien plants in Dhenkanal district of Odisha, India. International Research Journal of Biological Sciences, 4(2), 21-27. http://www.isca.in/IJBS/Archive/v4/i2/4.ISCA-IRJBS-2014-223.pdf

Park KeeWoong, Kolkman, J. M., Mallory-Smith, C. A., 2012. Point mutation in acetolactate synthase confers sulfonylurea and imidazolinone herbicide resistance in spiny annual sow-thistle [Sonchus asper (L.) Hill]. Canadian Journal of Plant Science, 92(2), 303-309. http://pubs.aic.ca/doi/full/10.4141/cjps2011-159 doi: 10.4141/cjps2011-159

PIER, 2018. Pacific Islands Ecosystems at Risk. Honolulu, Hawaii, USA: HEAR, University of Hawaii. http://www.hear.org/pier/index.html

PROTA, 2018. PROTA 4U web database. Grubben GJH, Denton OA, eds. Wageningen, Netherlands: Plant Resources of Tropical Africa. https://www.prota4u.org/

Rashid, A., Newman, J. C., O'Donovan, J. T., Robinson, D., Maurice, D., Poisson, D., Hall, L. M., 2003. Sulfonylurea herbicide resistance in Sonchus asper biotypes in Alberta, Canada. Weed Research (Oxford), 43(3), 214-220. doi: 10.1046/j.1365-3180.2003.00336.x

Schneider A, 2015. Sonchus in Lista de Espécies da Flora do Brasil. Rio de Janeiro, Brazil: Jardim Botânico do Rio de Janeiro. http://floradobrasil.jbrj.gov.br/jabot/floradobrasil/FB112277

Sekar, K. C., 2012. Invasive alien plants of Indian Himalayan Region - diversity and implication. American Journal of Plant Sciences, 3(2), 177-184. http://www.scirp.org/journal/PaperInformation.aspx?paperID=17533 doi: 10.4236/ajps.2012.32021

USDA-ARS, 2018. Germplasm Resources Information Network (GRIN). Online Database. Beltsville, USA: National Germplasm Resources Laboratory. http://www.ars-grin.gov/cgi-bin/npgs/html/tax_search.pl

USDA-NRCS, 2018. The PLANTS Database. Baton Rouge, USA: National Plant Data Center. http://plants.usda.gov/

Useful Tropical Plants, 2014. Useful Tropical Plants Database. http://tropical.theferns.info/

Vibrans H, 2009. Weeds of Mexico. Alphabetical list of species, ordered by genera. (Malezas de México. Listado alfabético de las especies, ordenadas por género). http://www.conabio.gob.mx

Vieira, B. S., Barreto, R. W., 2006. First record of Bremia lactucae infecting Sonchus oleraceus and Sonchus asper in Brazil and its infectivity to lettuce. Journal of Phytopathology, 154(2), 84-87. http://www.blackwell-synergy.com/servlet/useragent?func=showIssues&code=jph doi: 10.1111/j.1439-0434.2006.01064.x

Villaseñor RJL, Espinosa JG, 1998. Catalogue of weeds of Mexico. (Catálogo de malezas de México.), Mexico: Universidad Nacional Autónoma de México and Consejo Nacional Consultivo Fitosanitario.

Webb, C. J., Sykes, W. R., Garnock-Jones, P. J., 1988. Flora of New Zealand, Volume IV: Naturalised pteridophytes, gymnosperms, dicotyledons, Christchurch, New Zealand: Botany Division, DSIR.1365 pp.

Weeds of Australia, 2018. Weeds of Australia, Biosecurity Queensland Edition. http://keyserver.lucidcentral.org/weeds/data/media/Html/index.htm

Xu HaiGen, Qiang Sheng, Genovesi, P., Ding Hui, Wu Jun, Meng Ling, Han ZhengMin, Miao JinLai, Hu BaiShi, Guo JiangYing, Sun HongYing, Huang Cheng, Lei JunCheng, Le ZhiFang, Zhang XiaoPing, He ShunPing, Wu Yi, Zheng Zhou, Chen Lian, Jarošík, V., Pyšek, P., 2012. An inventory of invasive alien species in China. NeoBiota, (No.15), 1-26. http://www.pensoft.net/journals/neobiota/article/3575/an-inventory-of-invasive-alien-species-in-china

Distribution References

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

Broome R, Sabir K, Carrington S, 2007. Plants of the Eastern Caribbean. Online database. In: Plants of the Eastern Caribbean. Online database. Barbados: University of the West Indies. http://ecflora.cavehill.uwi.edu/index.html

CABI, Undated. CABI Compendium: Status inferred from regional distribution. Wallingford, UK: CABI

DAISIE, 2018. Delivering Alien Invasive Species Inventories for Europe. In: Delivering Alien Invasive Species Inventories for Europe. http://www.europe-aliens.org/

Danton P, Perrier C, Martinez RG, 2006. New catalogue of the vascular flora of the Juan Fernández Archipelago (Chile). (Nuevo catálogo de la flora vascular del Archipélago Juan Fernández (Chile)). In: Acta Botanica Gallica, 153 (4) 399-587.

Flora Mesoamericana, 2018. Flora Mesoamericana. (Flora Mesoamericana.). In: Flora Mesoamericana. St. Louis, Missouri, USA: Missouri Botanical Garden. http://www.tropicos.org/Project/fm

Flora of China Editorial Committee, 2018. Flora of China. In: 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

Florence J, Chevillotte H, Ollier C, Meyer JY, 2013. Botanical database of the Nadeaud Herbarium of French Polynesia. (Base de données botaniques Nadeaud de l'Herbier de la Polynésie Française (PAP))., http://www.herbier-tahiti.pf

Fonseca C R, Guadagnin D L, Emer C, Masciadri S, Germain P, Martin Zalba S, 2013. Invasive alien plants in the Pampas grasslands: a tri-national cooperation challenge. Biological Invasions. 15 (8), 1751-1763. http://rd.springer.com/article/10.1007/s10530-013-0406-2 DOI:10.1007/s10530-013-0406-2

GISD, 2018. Global Invasive Species Database (GISD)., http://www.iucngisd.org/gisd/

Hutchinson I, Colosi J, Lewin R A, 1984. The biology of Canadian weeds. 63. Sonchus asper (L.) Hill and S. oleraceus L. Canadian Journal of Plant Science. 64 (3), 731-744.

IABIN, 2017. Invasives Information Network (I3N). Inter-American Biodiversity Information Network., http://www.institutohorus.org.br/iabin/i3n/

Khanna K K, 2009. Invasive alien angiosperms of Uttar Pradesh. Biological Forum. 1 (2), 34-39. http://www.researchtrend.net

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Contributors

07/08/18 Original text by:

Julissa Rojas-Sandoval, Department of Botany-Smithsonian NMNH, Smithsonian Institution, Washington DC, USA

Distribution Maps