Once, a few years back, I was at a botanic garden in north Queensland. I saw a tree with a spectacular fruit hanging down, and being the curious (and slightly lax) plant nibbler I am, I was about to put it in my mouth. I stopped, because I realised it was a stupid idea to eat something I didn’t know. It was a cashew tree. Harmless, right? Nope. Apparently the fruit, when eaten, does a similar thing as battery acid to your throat. Not nice. I’ve learned my lesson.

Here are three of the most common poisonous plants around. Get scared. Really scared. But don’t really.

Horrid Hemlock
Conium maculatum

“True wisdom comes to each of us when we realize how little we understand about life, ourselves, and the world around us,” said Socrates once. The man credited as one of the founders of western philosophy was sentenced to death in 399 BC for corrupting the minds of the young men of Athens, by means of drinking hemlock.

According to Plato (his student at the time), after Socrates drank the poison “the man…laid his hands on him and after a while examined his feet and legs, then pinched his foot hard and asked if he felt it. He said ‘No’; then after that, his thighs; and passing upwards in this way he showed us that he was growing cold and rigid. And then again he touched him and said that when it reached his heart, he would be gone.” By Plato’s account, it seemed to be a relatively calm death, but that was a few thousand years ago so who really knows?

Then, in 1845 a Scottish tailor named Duncan Gow ate a sandwich made by his children. It was filled with foraged greens. Uh oh. Poor Mr Gow was dead a few hours later, according to Amy Stewart in her book Wicked Plants.

It was the last (and one suspects the only) lesson in botany the children ever got from their father, and one they would never forget,” she writes.

“Mr Gow stumbled about drunkenly, his limbs gradually became paralysed, and eventually the poison stopped his heart and lungs. The doctor attending the death reported that ‘the Intellect was perfectly clear until shortly before death.’”

Hemlock occurs in all states of Australia, except the Northern Territory, according to Parsons and Cuthbertson’s book Noxious Weeds of Australia (1992). “Deaths have occurred after people consumed the leaves in mistake for parsley, and roots instead of parsnips,” they assert. The confusion is obvious – Hemlock is in the same family, Apiaceae, as the above plants – the family also includes carrots, celery, fennel, coriander and dill. How one member of the family gets so toxic and the others not is beyond my botanical knowledge. Plants are strange/wonderful.

Conium maculatum grows up to 1.5 to 2 meters tall. It has hairless, hollow stalks covered with purple blotches. It flowers in late spring and early summer, producing lots of umbrella-shaped clusters of white flowers. It looks like a parsley or carrot plant on steroids.

Offensive Oleander
Nerium oleander

Oleander is one of the most ubiquitous garden plants of subtropical and Mediterranean climates the world over. In fact, oleander has been grown everywhere for so long that no one really knows where it originated. Despite it’s commonness, it’s a terribly toxic plant – all parts of it are poisonous to humans and most animals.

Apparently in 2002, 847 human exposures to oleander were reported to poison centres in the United States, but only three deaths were reported. There’s a bunch of stories around the plant – like the Californian woman who tried unsuccessfully to kill her husband for his life insurance payout by feeding him oleander leaves. It didn’t work. She tried again, putting antifreeze in his Gatorade. This, unfortunately, did work. The woman, Angelina Rodguigez, is now in prison, on death row.

It’s not all horrific though. The poison in Oleander – Oleandrin – has been tested for use as an anti-cancer medicine.

Studies have shown preliminary results in fighting cancer cells, but its not yet confirmed to work in humans. There also seems to be some potential for Oleandrin to be used to treat congestive heart failure, hepatitis C, and AIDS.

Oleander is the official flower of the city of Hiroshima, as it was the first to bloom following the atomic bombing of the city in 1945.

Cruel Castor Oil Plant
Ricinus communis

Ricinus communis is one of the most poisonous plants in the world. It’s seeds contain Ricin, an incredibly toxic substance that has been used to coat deadly scratch-and-sniff birthday cards from angry ex-boyfriends; posted in letters to US President Barak Obama; and perhaps most famously, used to assassinate Bulgarian dissident Georgi Markov on Waterloo Bridge in London in 1978.

Apparently it takes only four to eight seeds to kill a human, but ducks require over 80 seeds for a lethal dose. Bad stuff, eh?

But then there’s castor oil… It’s been used for hundreds of years as a laxative, to soothe muscles, in cosmetics, and even as a car engine oil! The Ricin in the seeds is removed during the distilling process, so you won’t poison yourself by ingesting it. Castor Oil plants have also been trialed as biofuel crops, as they’re fast growing, and can be planted in marginal land otherwise unusable for agriculture.

Due to it’s striking foliage Ricinis communis has long been used as a garden plant in warm climates. It’s also rather weedy. I walk past them daily on my way to and from work, admiring their tenacity and striking foliage as they inhabit the industrial back-blocks. I’ve always known they were poisonous, but I didn’t realise the extent till now.

But then, I should have known – they’re in the Euphorbiaceae family – that bunch of milky sapped poison mongers.

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Remember those anti-terrorism ads on Australian television years ago? “Be alert, not alarmed,” the government told us. Well, I’ve just become the government. Don’t be scared of plants, but don’t be too lax. The botanical world contains abundant beauty, and a whole heap of poison too. So, get educated. The more you know about plants, plant families, and all the botanical stuff, the more power to you to forage freely and with confidence.

Knowledge is power and ignorance isn’t bliss when you’re in hospital after eating hemlock, assuming it was wild parsnip.

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Featured image of Nerium oleander by Joaquim Alves Gaspar. Source: Wikipedia Commons