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Argemone ochroleuca Sweet 1828
pronounced: AR-gee-moh-nee ock-roh-LEW-kuh
(Papaveraceae – the poppy family)
common name: Mexican Prickly Poppy
Αργεμωνη (argemoné)was the ancient Greek name for a prickly poppy, Papaver argemone, so called because it was used medically to treat αργεμον (argemon), a white spot on the eye; ochroleuca is from ωχρος (ochros), yellow and λευκος (leukos) white, referring to the creamy yellow colour of the flowers.
The Mexican Prickly Poppy is commonly found as a weed of roadsides, mining dumps, rabbit warrens, recently cultivated paddocks, waste places, and over-grazed pastures. It often occurs as dense stands in sandy stream beds and alluvial flats associated with intermittent inland streams. The plants photographed were in Barbarra Street, Picnic Bay, on the bank of the recently re-directed floodwater channel. There is another very similar poppy, Argemone mexicana, that has longer and wider petals of a brighter yellow.
The plant grows 30 – 100 cm in height. It is a glaucous, erect, single- to several-stemmed annual with yellow sap. The stems are bluish green, pithy, smooth or slightly pubescent, and bear scattered stiff yellow prickles. The cotyledons are stalkless, narrowly lanceolate, curved and whitish turquoise with white veins, and are about 25 mm long by 1.3 mm wide at the first true leaf stage. The first true leaf is narrow with 3 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. The upper leaves are sessile and clasp the stem, and their shape is variable. The leaves are generally 6 – 20 cm long, 3 – 8 cm wide, deeply divided into 7 – 11 coarse irregular lobes, covered with a powdery bloom; the upper surface of the leaf has paler stripes along the vein. The margin of the leaf has wavy prickles at the tips of the lobes, as well as scattered on the underside of the leaf.
The flowers are creamy white to yellow, on a short stalk or sessile at the ends of branches, and are 3 – 6 cm in diameter. There are 3 hood-like sepals that are sparsely prickled with a sharp spine just below the apex. The sepals are shed as the flower opens. There are 6 delicate deciduous petals 2.5 – 3 cm long and 1.5 – 4 cm wide, and numerous stamens.
The fruit is a prickly ellipsoid capsule 2.5 – 5 cm long and about 2 cm 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 the ribs attached to the stigma, resembling the ribs of an umbrella. The numerous seeds are dark brown or black, globular, and about 1.5 mm in diameter.
This American native is found in most states of Australia, and is a widespread weed of the northern cropping areas.
Photographs taken 2010, 2011, Picnic Bay
Page last updated 16th July 2018