Argemone mexicana L.

Family

Papaveraceae

Synonyms

None

Vernacular Names

Geographical Distributions

Argemone mexicana is native to Mexico and the West Indies, but has become pantropical as an ornament and weed. It is naturalised in many Asian countries, from India, Indo-China to Taiwan, and southwards through Peninsular Malaysia, Java, the Lesser Sunda Islands, Sulawesi, to the Moluccas and the Philippines.

Description

Argemone mexicana is an annual, erect, branched, thistle-like herb that can grow up to 30-100 cm tall. It is smooth, containing yellow latex, pithy stem, with scattered prickles and firm taproot.

The lower leaves are crowded in a rosette, and with short petiole, whereas the higher ones are alternate, semi-amplexicaul, sessile, very variable in shape, sinuate-pinnatifid, measure 5-22 cm x 3-7 cm, white-variegated along the main veins and bluish green elsewhere.

The prickles are scattered along the margin and on the veins below. The inflorescence is terminal, with solitary flowers and sessile. The flowers are 3-merous and surrounded by 3 foliaceous bracts. There are 3 sepals which are valvate, vaulted, with horn below the acute apex, cylindrical, with few prickles and caducous at anthesis. There are 6 petals which are obovate, strongly plicate in bud, 1.7-3 cm long and bright yellow. There are many free stamens which are 7-12 mm long with anthers 2.5 mm long. The ovary is ovate, with long soft bristles, 8-10 mm long, with very short style, 3-6-lobed stigma and dark red.

The fruit is an ovoid capsule, 2.5-4 cm long, with rounded ribs, 3-6 valves, dehiscing from the apex to about 1/3, miter-shaped replum and sharp prickles. The seeds are globular, 1.5 mm in diametre, fine reticulate, black-brown, with prominent pale hilum. The seedling is with epigeal germination while the cotyledons are long and narrow.

Ecology / Cultivation

Argemone mexicana occurs mainly in regions with a pronounced dry season, on open waste grounds, along roadsides, in fields as a weed and along railways, mostly at sea-level, but sometimes up to 3000 m altitude. It is locally abundant, but on the whole scattered.

Line Drawing / Photograph

References

1. Plant Resources of South-East Asia No.12(2): Medicinal and poisonous plants 2.