1. Argemone mexicana Linnaeus, Sp. Pl. 1: 508. 1753.
蓟罂粟 ji ying su
Herbs, annual or occasionally short-lived perennial, 30-100 cm tall, usually stout. Stems mostly short, branched, with sparse explanate fulvous spines. Basal leaves dense; petiole 5-10 mm; blade glaucous with blue-green markings on veins, paler abaxially, broadly oblanceolate or obovate to elliptic, 5-20(-25) × 2.5-7.5(-8) cm, glabrous, sparsely sharply spiny on veins, base cuneate, margin pinnatipartite, apex acute; lobes undulate teeth, teeth apically spiny. Cauline leaves alternate, similar to basal leaves, but upper leaves smaller and sessile, often subamplexicaul. Flowers solitary, sometimes in few-flowered cymes. Pedicel very short. Flower buds ovoid, ca. 1.5 cm. Sepals 2(or 3), cymbiform, ca. 1 cm, apex spurred, glabrous or sparsely spiny. Petals 6, yellow or orange, broadly obovate, 1.7-3 cm, base broadly cuneate, apex rounded. Filaments ca. 7 mm; anthers narrowly oblong, 1.5-2 mm, coiling after dehiscence. Ovary elliptic or oblong, 7-10 mm, with explanate fulvous spines; styles very short; stigmas dark red, 4-6-lobed. Capsule oblong to broadly elliptic, 2.5-5 × 1.5-3 cm, sparsely fulvous spiny, 4-6-valved dehiscing from apex to 1/4-1/3 of length. Seeds spherical, 1.5-2 mm in diam., obviously tessellate. Fl. and fr. Mar-Oct. 2n = 28.
Naturalized along coasts, introduced in courtyards. Naturalized in Fujian, Guangdong, Taiwan, ?Yunnan; introduced in many provinces in China [native to Central and tropical America].
This is a widely cultivated plant which has become a naturalized weed in many parts of the world, particularly in subtropical regions. The seeds are poisonous.