Prickly poppy or Mexican poppy

Argemone ochroleuca
Herb
Alternate
Simple
Yellow
Cream
Variegated

A glaucous (blue-green) erect single to several stemmed annual with yellow sap,with a central taproot. It grows from 60 to 120cm in height. It has leafy stems that grow up to 60cm, with prickly lobed leaves. The flowers are showy and have a dark red 3 to 6 lobed stigma (glandular region at the tip of the style)

Common names 
Also known as: Mexican poppy, devil's fig, golden thistle of Peru, biniguy thistle, white thistle, yellow poppy, Mexican thistle, Mexican prickle poppy,
Family 
Papaveraceae
Deciduous 
No
Flowering time 
Flowering occurs mostly during spring and summer, but may also occur throughout the rest of the year.
Native/Exotic 
Exotic
Origin 
Native to tropical America but its exact native range is disputed
Notifiable 
No
State declaration 
Nil
Council declaration 
Class R – Reduce populations
Known distribution 

Locations within which Argemone ochroleuca is naturalised include Australia, Africa, tropical Asia, New Zealand and some oceanic islands with warm climates.

Habitat 

Argemone ochroleuca is commonly found as a weed of roadsides, mining dumps, rabbit warrens, recently cultivated paddocks, degraded land, and over-grazed pastures. It often occurs as dense stands in sandy stream beds and alluvial flats associated with intermittent inland streams.

Habit 

A prickly glaucous herb, usually 35-40 cm tall; young stem whitish purple or violaceous, fading with age

Impact and control methods 

This species is an agricultural weed. Harvesting crops in field infested with Argemone ochroleuca can be painful.

It has been introduced into Australia, Africa, tropical Asia, New Zealand and a number of oceanic islands where it has become invasive. It is most common in disturbed areas such as roadsides, mining dumps, rabbit warrens, recently cultivated paddocks, degraded land and over-grazed pastures. This species produces a large number of seed which can be accidentally introduced into new areas as a seed contaminant. It is often a problem in agricultural land but also has the potential to outcompete native species and decrease biodiversity. A. ochroleuca is toxic to humans and livestock and has thorny spines which can cause injury.

Stem and leaves 

Stems are bluish-green, pithy, smooth or slightly pubescent (covered with short hairs). The stems grow 30 to 100cm high, with scattered stiff yellow prickles. The seed leaves are stalkless, narrow lance shaped, curved and whitish-turquoise with white veins and are about 26mm long by 1.3mm wide at the first true leaf stage. The first true leaf is narrow with three triangular, pointed lobes at the tip and a tapering base. The second true leaf is also narrow but is deeply lobed. The leaves are bluish-green and alternate. The basal leaves are slightly stalked and crowded into a dense rosette (a cluster of leaves at the base of a plant often lying flat against the ground). The upper leaves are sessile (without a stalk) and clasping the stem, the shape being variable. The leaves are generally 6 to 20cm long, 3 to 8cm wide, deeply divided into 7 to 11 coarse irregular lobes, covered with a powdery bloom; the upper surface of the leaf has paler stripes along the veins. The margin (edge) of the leaf has wavy prickles at the tips of the lobes as well as scattered on the underside of the leaf.

Flowers and fruits 

Flowers are creamy white to yellow, on a short stalk or sessile (without a stalk) at the ends of branches, and are 3 to 6cm wide in diameter. There are 3 hood-like sepals that are sparsely prickled with a large spine just below the apex. The sepals are shed as the flower opens. There are 6 delicate deciduous petals that are 2.5 to 3cm long and 1.4 to 4cm wide. There are numerous stamens. The sepals are shed as the flower opens. The fruit is a prickly ellipsoid capsule that is 2.5cm to 5cm long and 2cm in diameter crowned with a persistent style and narrowed at both ends and widest below the middle. When the fruit is ripe it opens from the apex downwards, splitting away from the style with ribs attached to the stigma and so resembling the ribs of an umbrella. The seeds are numerous dark brown or black and globular and are about 1.5mm in diameter.

Reproduction and dispersal 

A. ochroleuca reproduces by producing a large numbers of seed; up to 400 seed can be produced per pod and 20,000 per plant. Most seeds fall around the parent plant but some are dispersed by water, mud adhering to boots and farming machinery and livestock. The seeds can also be dispersed by birds. Seeds have a dormancy period of up to a few months and may remain in the soil seed bank for up to seven years. This species can be spread as a contaminant of crop grains/seeds.