Author: Cheryl Haxen

The first image is Argemone ochroleuca, a species very similar to Argemone mexicana. The latter, image 2, has flowers of a much darker yellow.

Both have become naturalised in many places including Australia, and can be found in even the driest places, as A. ochroleuca is seen flourishing here on a vacant lot where almost everything else had succumbed to drought.

Argemone refers to the silver colour of the plant and 'ochroleuca' means pale colour. Those spines are painful to touch and the whole plant a problem for our agriculture. Note the huge developing pods which contain many round black seeds.

The entire plant is toxic to grazers, although few livestock will consume it. The problem is partly the difficulty of dealing with the painfully prickly plants, but mostly with contamination of harvested crops with seeds which are toxic to humans, and to livestock via fodder and feeds. Both are declared in WA and Northern Territory. Both species if damaged ooze a bright yellow latex, containing a cocktail of six toxic alkaloids. The seeds contain more than 25% of a yellow toxic oil, and latex from the pods had a further two toxic alkaloids.

Seeds of A. mexicana are common contaminants of mustard crops, being difficult to differentiate especially in the darker seeded mustard. Poisoning is common in India, Fiji, South Africa and other places as the mixed seeds are crushed to paste or pressed for oil. Contamination of less than 1% causes epidemic dropsy...swelling of limbs resulting from kidney and liver damage, a range of other symptoms and sometimes death.

Unfortunately many outbreaks of poisoning in these poor countries are caused by deliberate adulteration of mustard, sesame and sunflower oils in order to maximise production and profits. In Australia the seeds are graded out of larger seed crops and similar smaller crops carefully checked.

However, paradoxically, as is the way with so many plants containing powerful compounds, Argemone is widely used in traditional medicine for range of illnesses. Not recommended! In Mali a tea made from roots or leaves is used to treat malaria and some research is no being carried out scientifically to check the claims. The oil is also being investigated as a possible bio-diesel and insecticide.

The good news is that Agetal analysts are able to accurately identify Argemone seeds in samples. By naked eye they are easily mistaken for canola, mustard and several weed species. However, when magnified under the microscope they are unmistakable, and we are always alert to the possibility.