Parthenium hysterophorus | Santa-Maria

Pre 2017

2017 - 2020


Legal status

Regulated invasive species of Union concern under the European Regulation on the prevention and management of the introduction and spread of invasive alien species [1143/2014].


Not assessed

Irish status


Introduction pathways - 1

Transport Contaminant

Introduction pathways subclass - 1

Contaminant nursery material, Seed contaminant

Introduction pathways - 2

Transport Stowaway

Introduction pathways subclass - 2

Machinery/equipment, Vehicles

NAPRA Ireland risk assessed


Species Biology


Upright blue or grey green annual or short-lived perennial herb. Grows vigorously and can reach 2m tall (EPPO, 2014b; GISD, 2015). Has a deep taproot. Leaves are alternate, covered in fine hairs, finely divided, 3-20cm long and 2-10cm wide (EPPO, 2014b). Small white flowers have 5 distinct corners and are borne on panicles. Each flower produces 4-5 brown, wedge-shaped seeds. Stem is many branched and becomes woody as it ages.


Rapidly colonises areas of poor ground cover e.g. roadsides or overgrazed pastureland. Appears to dominate by means of allelopathy rather than competition for scarce resources (EPPO, 2014b). Produces several chemicals which reduce germination rates of crops, native plants and trees (EPPO, 2014a). Highly successful in areas that are disturbed frequently (EPPO, 2014a). Withstands a wide range of temperatures, and soil types but prefers a neutral or alkaline pH (EPPO, 2015). All parts of the plant are allergenic, causing dermatitis, hay fever and asthma (Q-bank, 2017). Severe allergic reactions can occur in livestock, particularly horses (European Commission, 2017. The plant is also mutagenic (Q-bank, 2017) and toxic and can kill cattle when large quantities are consumed (Australian Weeds Committee, 2012). Meat from cattle eating the weed is often tainted (Australian Weeds Committee, 2012; GISD, 2015).


Reproduces by the prolific production of seed, up to 100,000 seeds per plant (GISD, 2017). Pollinated by both insects and wind (Gupta & Chanda, 1991). Summer annual but can germinate at any time of the year if conditions are right (Australian Weeds Committee, 2012; EPPO, 2014b). Can germinate, flower and set seed within 4 weeks (EPPO, 2014a) so 4-5 generations can be produced in a season (Australian Weeds Committee, 2012). Seeds remain viable for 8-10 years (Q-bank, 2017).

Pathway and vector description

Pathways of spread from country to country include seed contamination of cereal, grass or birdseed; second hand machinery; road vehicles; growing medium for potted plants or travellers shoes or clothing (EPPO, 2014a). Once established the plant spreads locally by seed dispersal on wind, water or animals (EPPO, 2014a). Flood events can disperse seeds long distances (EPPO, 2014a). Can also be spread via farmyard manures and composts (EPPO, 2014a).

Mechanism of impact

Competition, Poisoning/Toxicity

Management approach

There is currently an EU wide ban on the sale, growing and keeping of this plant (European Commission, 2017).

Eradication attempts are usually unsuccessful but are possible for small and isolated populations if the invasion is detected early (<4 weeks). Continual monitoring of the area following control methods will be necessary for a minimum of 7 years (EPPO, 2014a; EPPO, 2015).


Hand-pulling is an effective method but the health risk to personnel must be considered and they must be suitably attired (EPPO, 2015). Must be carried out before flowering and plants must be pulled completely or they will resprout (EPPO, 2015).

Hand-hoeing is also effective but will need to be carried out several times a year (EPPO, 2015).


Ploughing before seed set and then establishing pasture may be effective (Australian Weeds Committee, 2012; EPPO, 2015; Q-bank, 2017).


2,4 D, glyphosate and paraquat are effective. Apply when plants are small and grasses are actively growing so they can re-colonise the area (EPPO, 2014a; EPPO, 2014b; Q-bank, 2017). Most effective when applied at rosette stage (EPPO, 2015). A selective pre-emergent spray can be used after ploughing before crops are planted (Australian Weeds Committee, 2012; EPPO, 2015). There are reports of herbicide resistance (EPPO, 2014a).


Herbicides made using the oils of other allelopathic plants such as Eucalyptus can be used (Q-bank, 2017). Competition is an important means of control so good grassland management is essential (Australian Weeds Committee, 2012).


Plants should be disposed of by bagging and burning (EPPO, 2015).

Broad environment


Habitat description

Disturbed and fallow ground; riparian zones; pastures; perennial and arable crops; orchards; forests; rail and roadsides; wasteland and floodplains.

Species group


Native region

North America, South America

Similar species

Can be confused with Artemesia, Ambrosia and Jacobaea when not in flower (Q-bank, 2017).


World distribution(GBIF)

Introduced to Australia, Asia, Africa and the Pacific. In the EPPO region it is so far only confirmed in Israel. It is suspected in Egypt and has been casual in Belgium and Poland. Countries in the Mediterranean region are considered to be most at risk of invasion (EPPO, 2014a).

Native distribution

Native to North, South and Central America.

Temporal change

Records submitted to Data Centre in 2022

The following map is interactive. If you would prefer to view it full screen then click here.

How can you help

Report any sightings to the National Biodiversity Data Centre.



Australian Weeds Committee (2012) Parthenium (Parthenium hysterophorus L.) strategic plan 2012–17, Weeds of National Significance, Australian Government Department of Agriculture, Fisheries and Forestry, Canberra. Site accessed 21 September 2017.

CRC for Australian Weed Management and the Commonwealth Department of the Environment and Heritage (2003) Weeds of national significance -Weed management guide - Parthenium weed – Parthenium hysterophorus. Site accessed 21 September 2017.

European and Mediterranean Plant Protection Organisation (EPPO) (2015) National regulatory control systems. PM 9/20 (1) Parthenium hysterophorus. EPPO Bulletin 43 (3), pp 456-461. DOI: 10.1111/epp.12252 Site accessed 20 September 2017.

European and Mediterranean Plant Protection Organisation (EPPO) (2014a) Pest risk analysis for Parthenium hysterophorus. EPPO, Paris. Site accessed 20 September 2017.

European and Mediterranean Plant Protection Organisation (EPPO) (2014b) Data sheets on invasive alien plants. Parthenium hysterophorus L. Asteraceae – Parthenium weed EPPO Bulletin 44 (3), pp 474-478. DOI: 10.1111/epp.12168 Site accessed 20 September 2017.

Global Invasive Species Database (GISD) (2015). Species profile Parthenium hysterophorus. Available from: Site accessed 20 September 2017.

Gupta, S & Chanda, S (1991) Aerobiology and some chemical parameters of Parthenium hysterophorus pollen, Grana, 30:2, 497-503, DOI: 10.1080/00173139109432017 Site accessed 21 September 2017.

Q-bank (2017). Q-bank Factsheet Parthenium hysterophorus L. Santa Maria feverfew. Site accessed 20 September 2017.

CABI Datasheet

DAISIE Factsheet