Driving back after our last safari, I stopped the car where a patch of kateli (Argemone mexicana) was in flower. I use the common Hindi name for it, although it is not an Indian plant. A less popular name, vilayati datura, is actually more explanatory. It says that the plant is exotic, and also indicates that it is poisonous in some way. Livestock avoid it, perhaps largely because of the thorns. But it can kill if they eat enough of it.
The Encyclopedia of Food Safety sent shivers down my spine with the warning that its oil contains “the toxic quaternary benzophenanthridine alkaloids sanguinarine (approximately 90%) and dehydrosanguinarine (approximately 5%) with lesser quantities of cheletrythrine and coptisine, and small quantities of berberine and protopine, which are isoquinoline alkaloids.” I didn’t understand a word of this, but it sounded menacing. Before cooking oil became available in tamper-proof packaging, there were some incidents of cooking oils adulterated with kateli oil. As you might expect, this resulted in deaths. All plants in the poppy family (Papaveraceae), to which it belongs, harbour toxins.
I’ve grown up seeing this plant in the kinds of degraded land which a city kid finds fascinating: the sides of roads, abandoned half-built houses, even in the cracked concrete of parking lots. Mumbai doesn’t have much; perhaps it is too wet. But across most of the dry Indian planes, even as high up as the lower valleys in Bhutan, the prickly green leaves spread a carpet over wasteland, a carpet which sprouts showy yellow flowers through autumn and winter. Now, with the right tool I could look closely at the flower. Some would hesitate to say it is beautiful, since it has six petals, and six is not a Fibonacci number. But I’m not one of them.
Knowing that it was exotic sent me on an interesting chase. It seems to be found across the tropics; it can be found across south and south-east Asia. I followed its recent progress across Africa: from Kenya to Angola across the continent and up and down the coast. It has been spreading across southern Europe and the Mediterranean basin recently. The genus Argemone contains 24 species, not all of which are equally invasive. The center of diversity seems to be in south-western US, but it is spread across central and south America, including the Andean region. A single species has been found in Hawaii. A study made in the Ngorongo bio-reserve found that seeds traveled hidden in construction material, and then were dispersed in the tyres of vehicles. Perhaps that’s how the invasion of the prickly poppy started.