Prickly or Mexican poppies are in Family Papaveraceae > Subfamily Papaveroideae > Tribe Papavereae.
Argemone mexicana and A. ochroleuca subsp. ochroleuca both occur in Queensland where they are declared weeds.
They are very similar in appearance with A. mexicana having brighter yellow flowers.
Argemone subfusiformis subsp. subfusiformis is also similar.
They are upright, much branched herbs that grow to just over 1 m high.
The shiny stems and leaves exude a yellow sap when damaged.
Initially the leaves are in a basal rosette but as the stem grows the basal ones die off.
The leaves are alternately arranged.
They are up to 15 cm long and a blue-green or grey-green with pale whitish veins.
The leaf margins are deeply divided or toothed with small spines at the tips.
The oblong flower buds, to 18 mm long, are also covered in spines.
The calyx has three sepals, each of which has a horn-like projection at the tip, longer in
A. subfusiformis subsp. subfusiformis than the others.
The flowers, up to 7 cm across, have 6 petals.
In A. mexicana they are bright yellow and in the others they are cream or pale yellow.
There up to 75 stamens and a lobed, purple stigma.
The fruit is a spiny ovoid capsule with 5 (3-6) chambers containing tiny, dark round seeds.