Quick Facts

Quick facts

• Mexican Poppy (Argemone ochroleuca) is an annual erect prickly annual herb to to 1.5 m tall, with a stout- tap-root mottles grey-green and cream leaves, with pale yellow to cream flowers.
• It reproduces by seed with a single plant able to produce 30, 000 seeds, spread by water, contaminated soils, agricultural produce, machinery and vehicles.
• It is common around mainland Australia from Temperate to arid regions, most common in Queensland, New South Wales and Western Australia, but is widespread throughout much of Australia.
• It is extremely poisonous to humans and animals, but instances of stock poising are rare due to it being unpalatable to stock.
• It establishes readily on wasteland and overgrazed pastures, sandy seasonally dry creek lines, especially where competition from other species is minimal.
• Impacts some crops such as sugarcane, cereals and vegetables, in arid grazing areas especial sandy distributed areas.
• Good pasture management is effective in reducing the impact and preventing the invasion of Mexican Poppy.

What Does It Look Like?

What is it?

Mexican Poppy (Argemone ochroleuca ) is an erect prickly annual herb to sub-shrub, growing to 1 m or occasionally to 1.5 m tall, with a stout tap-root. Initially, the the plant produces basal leaves, 2–20 cm long, forming a rosette at ground level, but soon wither as an erect stem is produced with stem leaves. Seedlings have long, linear, sabre-shaped cotyledons, are hairless, pale-greenish-blue in colour and lack a petiole (Dellow 2005). The first true leaves of the seedlings are club-shaped, irregularly toothed with the teeth ending in spines, and are pale-greenish-blue in colour with whitish markings (Dellow 2005). The stems are sparsely spiny and exude a yellow sap when damaged.  All leaves are bluish-green or greyish-green in colour, usually with whitish veins and markings. The leaves are spiny and prickly, 2–20 cm long and 1–6 cm wide, sometimes much larger, hairless, deeply divided in to several lobes with yellowish spines about 5 mm long with leaf margins with many other spiny smaller yellowish spines along the edges. The upper or stem leaves are arranged alternately along the stems. Prior to flowering, plants may be mistaken for thistles due to the spiny leaves and stems.

The flowers of Mexican Poppy are 3–7 cm in diameter and consist of six, pale yellow to cream petals, each petal about 2.5–3.5 cm long. The 3 sepals surrounding the flower are also spiny, ovate (shaped like a section through the long axis of an egg and attached by the wider end), 15–20 mm long  including a roughly 8 mm long terminal spine, with about 8 spines in total. Numerous (30-50)  bright yellow stamens and a purple stigma occur in the centre of the flowers.

The fruits are spiny, oblong-oval spiny capsules, 2–5 cm long and 1–2 cm wide, with up to 20 spines per valve (section of the fruit). Capsules contain numerous small pitted seeds 1–2 mm in diameter.

The nomenclature of this species is somewhat complicated. It has sometimes been referred to in Australia as A. mexicana or A. mexicana var. ochroleuca. Argemone mexicana is very similar in appearance but is less common than A. ochroleuca. It occurs in Perth, Western Australia, south-eastern Queensland and north-eastern New South Wales (Ownbey 2007). To confuse matters even further, both species are referred to as Mexican Poppy. Argemone mexicana differs from A. ochroleuca in that it has bright yellow flowers as opposed to cream or pale-yellow flowers, and globular flower buds as opposed to the oval buds of Argemone ochroleuca.

For further information and assistance with identification of Mexican Poppy contact the herbarium in your state or territory.

Flower colour

Yellow, Cream

Growth form (weed type/habit)

Herb

Where it currently grows? Preferred habitat

Mexican Poppy grows in environments ranging from temperate to tropical, and from arid to humid. It most commonly occurs in semi-arid, sub-tropical and temperate regions. It is a weed of many varied habitats, including roadsides, railway lines, waste areas, disturbed sites, degraded pastures, crops and fallow ground (Weber 2003; Navie 2004; Ownbey 2007). It is often recorded as having an affinity for sandy river flats and ephemeral watercourses (Auld & Medd 1987; Parsons & Cuthbertson 2001). Establishment of this plant most commonly takes place on disturbed sites and bare ground (Weber 2003).

Are there similar species?

The common name, Mexican Poppy, is also applied to another species of Argemone, A. mexicana. 

A. mexicana occurs as a weed in Queensland and Western Australia. It differs from A. ochroleuca by its bright yellow flowers and globular flower buds, as opposed to egg-shaped buds of A. ochroleuca. A. mexicana has a more tropical distribution in Australia (Auld & Medd 1987). 

Another similar species that is also naturalised in Australia is American Poppy (Argemone subfusiformis G.B.Ownbey subsp. subfusiformis). This species is known to be naturalised only in north-eastern New South Wales (Ownbey 2007). It has flowers that are generally larger than those of the Mexican Poppy and a less spiny capsule (Ownbey 2007). When not flowering it could be mistaken for a Thistle due to the presence of prickles on the stems and leaves.

Why Is It A Weed?

What are its impacts?

Mexican Poppy was included in the list of 71 species that were nominated by state and territory governments for assessment as Weeds of National Significance (WONS). Following an assessment process, Mexican Poppy was not included as one of the 20 WONS. However, it remains a weed of potential national significance. Under suitable conditions, Mexican Poppy forms large and dense populations that can impede the movement of stock and wildlife and displace native vegetation (Weber 2003). Seedlings are poor competitors (Weber 2003).

Agriculture: Widely distributed in the pastoral/rangeland areas, mainly along river systems, moist flats and sand dunes in arid areas. Mexican Poppy is also present in some agricultural areas, but does not compete well with crops or in managed pastures (DPIRD WA 2020). It grows well in sugarcane and cereal crops but is generally not regarded as an aggressive crop weed in Australia (Parsons & Cuthbertson 2001). It establishes readily on wasteland and overgrazed pastures (Parsons & Cuthbertson 2001). The prickly fruits can become entangled in wool, reducing its value considerably (Parsons & Cuthbertson 2001). Mexican Poppy is a host for Verticillium and the Tomato Spotted Wilt Virus (Bromilow 2001). Mexican poppy is poisonous to stock and humans, but is rarely eaten by stock. Reported cases of poisoning are rare as livestock tend to avoid it in the field due to its unpalatable bitter yellow sap. Contamination of stock feed with seeds of Mexican poppy may result in poisoning (DPI NSW 2019; Parsons & Cuthbertson 2001). Poisonings may occur as a result of hay and chaff containing traces of the plant (Parsons & Cuthbertson 2001). 

Human impacts: It is suspected of being toxic to animals and humans due to the presence of alkaloids in all parts of the plant.  (Parsons & Cuthbertson 2001). Poisonings in humans have occurred by the consumption of oils contaminated with the plant (Parsons & Cuthbertson 2001). For further information on the toxicity of Mexican Poppy see Everist (1974) and Parsons & Cuthbertson (2001). If poisoning occurs and:

• the patient is unconscious, unresponsive or having difficulty breathing dial 000 or get to the emergency section of a hospital immediately.
• the patient is conscious and responsive call the Poisons Information Centre on 13 11 26 or your doctor.
• If going to a hospital take a piece of the plant for identification.

How does it spread?

Reproduction of Mexican Poppy occurs by seed. It is estimated that a single plant can produce up to 30 000 seeds per year (Parsons & Cuthbertson 2001; Weber 2003). Seeds of Mexican Poppy usually fall close to the parent plant. Seed is readily dispersed by moving water, especially where plants grow in riparian habitats and on terrain where erosion and runoff occurs. Contaminated soil, fodder, agricultural produce, vehicles and the fur and hooves of livestock are also vectors for transport of Mexican Poppy seed (Parsons & Cuthbertson 2001). Plants have been known to break off from the base and be blown long distances, scattering seed along the way (Smith 2002).

What is its history in Australia?

It is thought that Mexican Poppy was accidentally introduced into Australia as a contaminant of wheat seed. It was first recorded from Sydney Cove, New South Wales, in 1844 (Parsons & Cuthbertson 2001), although the first herbarium record listed on AVH is from New South Wales in 1886 (AVH 2021). It now occurs as a weed throughout the country (Parsons & Cuthbertson 2001).

How To Manage It?

Best practice management

Prevention: As is the case with many annual weeds, control should be aimed at the prevention of seed formation (Parsons & Cuthbertson 2001; Weber 2003).

Non-chemical control: Successful control may be achieved by hand-pulling, grubbing or cutting plants before any fruits ripen (Parsons & Cuthbertson 2001; Weber 2003). Good pasture management is effective in reducing the impact and preventing invasion of Mexican Poppy. Seedlings do not compete well with perennial crop and pasture species, nor does it compete well with established pasture (Parsons & Cuthbertson 2001). Slashing and mowing reduces the amount of seeds produced 

Chemical control: Seedlings can be controlled effectively with herbicide or by mowing (Parsons & Cuthbertson 2001, Weber 2003).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Seeds germinate at any time of the year provided adequate moisture is available. Under normal seasonal conditions, young plants form a rosette during winter and produce flowering stems during spring. Flowering of Mexican Poppy can occur throughout most of the year, but most often during spring and summer (Navie 2004). Mature seed remains dormant for up to three months after being shed from the parent plant (Parsons & Cuthbertson 2001) and can remain viable for several years (Department of Agriculture and Food 2007).

Where Is It Found?

Which states and territories is it found?

NSW, NT, QLD, SA, TAS, VIC, WA

What areas within states and territories is it found?

Mexican poppy can grow in a wide variety of climates from semi-arid to wetter subtropical climates. It tolerates a wide variety of soil types and can grow well in soils with low nutrient levels (DPI NSW 2019). 

Mexican Poppy is widespread in Queensland and New South Wales, especially in sub-coastal regions (Navie 2004). It also occurs in the western parts of Western Australia, south-eastern and arid South Australia and he Northern Territory and well as a few areas in Victoria  (AVH 2021; Navie 2004). In Tasmania, it has only been recorded as a weed of cultivated ground from two locations, although it is currently thought to be absent from the state (Buchanan 2007, pers. comm.).

Mexican Poppy is widespread in temperate and tropical regions of the world and is present as a weed in Argentina, India, Madagascar, Mauritius, Morocco, Nicaragua, Pakistan, the Philippines, Puerto Rico, South Africa, Tanzania (Parsons & Cuthbertson 2001) and New Zealand (Roy et al. 2004).

Where does it originate?

Mexican Poppy is native to the upland, less humid parts of Mexico (Ownbey 2007).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

NT 

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Argemone ochroleuca

Other scientific names (synonyms)?

• Argemone mexicana L. var. ochroleuca (Sweet) Lindl.
• Argemone mexicana L. (misapplied by Curtis, W.M. & Morris, D.I. 1975, Angiospermae: Ranunculaceae to Myrtaceae. The Student's Flora of Tasmania Edn 2. 1: 28.)

Does it have other known common name(s)?

Prickly Poppy, Mexican Thistle, Mexican Pricklepoppy, White Thistle, Yellow Poppy, Devil's Fig