Mexican poppy (Argemone ochroleuca subsp. ochroleuca)

Mexican poppy is a small plant with spiny leaves and bright yellow flowers. It is poisonous to livestock and people.

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How does this weed affect you?

Mexican poppy:

is poisonous to people and animals
contains yellow sap that can cause skin irritations
has spines that can cause injuries
competes with native plants, especially in seasonal creek and river beds
contaminates or spoils crops, including grains, sugarcane and vegetables
leaches chemicals that inhibit the germination of seeds including wheat, sorghum and millet
has spiny fruit that cling to, and degrade the quality of wool
hosts crop diseases.

Human health

All parts of Mexican poppy plants are poisonous. They contain isoquinoline alkaloids. Poisoning can occur if grains or cooking oils are contaminated by Mexican poppy seeds. It can cause glaucoma and oedema.

The sap can cause skin irritations.

Livestock poisoning

Chickens have been poisoned by feed contaminated with Mexican poppy seeds. The seeds limit growth, reduce egg production and can cause death in poultry. Although poisonous to grazing animals, Mexican poppy is rarely grazed by livestock due to its unpalatable sap.

What does it look like?

Mexican poppy is an erect, spiny annual herb growing up to 1.5 m high. The stems contain yellow sap.

Leaves are:

bluish green or greyish green with white mottling
up to 12 cm long
toothed or irregularly lobed with a small yellow spine at the end of each lobe
in a dense rosette at the base of the plant and alternate along the stem
stalked at the base of the plant, stalkless and clasping higher up the stem.

Flowers are:

cream to pale yellow with 6 petals
3-6 cm in diameter
present from spring to summer.

Fruit are:

capsules containing up to 400 seeds
covered in rigid spines and with an opening at the top of the capsule
shiny blue-green
oval or oblong shaped
2–4 cm long.

Seeds are:

brown or black
pitted
1.5 mm in diameter.

Stems are:

bluish green
smooth or slightly hairy with scattered yellow spines.

Similar looking plants

American poppy (Argemone subfusiformis), which is also a weed, is very similar looking. It has brighter yellow flowers and the capsule has fewer spines.

Where is it found?

Mexican poppy has been found in all regions of NSW.

It is native to Central America including Mexico.

What type of environment does it grow in?

Mexican poppy grows in subtropical, temperate and semi-arid climates. Plants grow in full sun and are drought tolerant. They tolerate a wide variety of soil types and grows well in light sandy soils with low nutrient levels.

Mexican poppy grows:

in degraded areas including roadsides, railway lines and mining dumps
in riparian areas, sandy stream beds and alluvial flats
amongst crops
in degraded pastures.

How does it spread?

By seed

Each plant can produce tens of thousands of seeds. Seeds germinate at any time of the year provided adequate moisture is available. They can stay dormant for many years.

Seeds are spread:

by water
in mud stuck to machinery
by animals, stuck on fur, wool or hooves
on clothing or footwear
in contaminated fodder and grain
in contaminated sand and soil.

References

Everest. S. L. (1981). Poisonous Plants of Australia. Revised edition. Angus and Robertson.

Northern Territory Government (n.d.) Mexican poppy(Agemone ochroleuca) weed note Retrieved 25 June 2026 from: https://environment.nt.gov.au/media/docs/weed-note/weed-note/Mexican-poppy-weed-note.pdf

Parsons, W.T., & Cuthbertson, E. G. (2001). Noxious weeds of Australia. CSIRO publishing.

PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 25 June 2026 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=in&name=Argemone~ochroleuca+subsp.~ochroleuca

Sanaa, A. I., & Moussa, I. (2012). Invasiveness of Argemone ochroleuca Sweet in various habitats in Taif, Saudi Arabia. African Journal of Plant Science, 6(15), 433-438.

More information

Control

Where possible, control Mexican poppy before it seeds.

Prevention

Clean down machinery, boots and clothing that has been in an infested area before moving to a site without Mexican poppy.

Pasture management

Mexican poppy does not compete well with perennial pastures. Maintain ground cover and avoid overgrazing to limit infestations.

Hand removal

Small plants can be pulled or dug out. If plants have started fruiting be careful not to spread the seeds.

Ensure that protective clothing is worn to avoid contact with the spines and the sap.

Disposal

Once dug out, plants can be burnt to kill the seeds. Check burn sites regularly and remove any seedlings. Contact your local council for other methods of disposal.

Slashing/mowing

Seedlings in pastures can be managed by mowing. Do not mow fruiting plants as this will spread the seeds

Herbicides

Spray actively growing plants at the rosette stage before flowering.

Herbicide options

WARNING - ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au

See Using herbicides for more information.

2,4-D LV ester 680g/L (Estercide® Xtra)
Rate: 800 mL to 1.15 L per ha
Comments: Spray rate for pastures (non-legume). Spray rosette stage before flowering.
Withholding period: Do not graze or cut for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

Glyphosate 360 g/L (Various products)
Rate: 10 mL per 1 L of Water
Comments: For general weed control in domestic areas, commercial, industrial public service areas, agricultural buildings and other farm situations.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

Biosecurity duty

The content provided here is for information purposes only and is taken from the NSW Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area	Duty
All of NSW	General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.

For technical advice and assistance with identification please contact your local council weeds officer.

Reviewed 2026