Toxic plants and natural remedies

Brunfelsia, or the Yesterday Today Tomorrow plant, is highly toxic to dogs but fortunately few dogs eat flowers.

Brunfelsia, or the Yesterday Today Tomorrow plant, is highly toxic to dogs but fortunately few dogs eat flowers.

My mention of the toxicity of oleander in Plant Collector last week yielded the following comment via Twitter:
I remember seeing a photo as a kid of someone who had made a bonfire with oleander. Poor guy looked like he had been doused in acid. He inhaled some smoke and wound up in intensive care with lung damage.

Before you rush out to dispose of your oleander – if you have one – you may like to ponder that if you are determined to rid your garden of all poisonous and therefore dangerous plants, you will have to remove all daphnes, laburnum, alocasias, rhus, karaka, brunfelsia, aroids, colchicums, tulips and a whole lot more. You will end up removing half your garden. There is a certain folly to thinking that you can make your garden safe for small children and dogs by only growing non-toxic plants. Goodness, even oak and yew can be toxic to dogs.

The plant kingdom is still the prime source for most of our pharmaceutical compounds and our poisons. Aspirin was derived from willows, morphine from poppies. When a natural compound to treat cancer was isolated in Taxus baccata, British gardeners were urged to deliver their yew clippings to depots for a few years so researchers could isolate the relevant chemical compound.

Fortunately for the plant kingdom, scientists then set about re-creating the desired plant sequence in laboratories to avoid the problems of depleting natural resources.

I am sure it was Agatha Christie who alerted her readers to the fact that laburnum seeds are highly toxic and can in fact be used to poison off one’s enemy. But there are so many other sources of poisons. Cyanide is a natural compound, found in peach and apricot kernels, cassava, even apple pips along with many other sources. Ricin, one of the deadliest natural toxins, is derived from the seed of the castor plant (Ricinus communis) – as indeed is castor oil. The castor plant is highly decorative and still found in some gardens and public plantings. It was ricin that was used to murder Bulgarian dissident, Georgi Markov, in London back in 1978. He was poked with an umbrella spike in the street which transferred the poison capsule into the back of his thigh. It took three days for him to die.

Most of the alocasias are toxic but this one particularly so. We are cautious handling it in the garden

Most of the alocasias are toxic but this one particularly so. We are cautious handling it in the garden

All this gives lie to the feel-good myth that “if it is natural, it must be good for us”. These can be powerful substances with unexpected side effects for the unwary. The potential for enthusiastic amateurs to get it wrong is just as great today as earlier.

The world has been grappling with the thin line between safety and danger in plants for over two millennia. It was the Ancient Greek Theophrastus, back before Christ was born, who is credited with first starting to try and sort out the plant kingdom into some comprehensible form, a task that was not completed until Carl Linnaeus in the 1700s. When humankind depended entirely on wild-gathered plant material for medicine, the potential for matters to go badly wrong was enormous. The majority of the populace has some difficulty in recognising different plants, even more so if they look similar. It is highly likely that there were a fair number of people out there a-diggin’ (for roots or bulbs), a-cuttin’ (for foliage or flowers) and a-gatherin’ (seeds) who subscribed to the “near enough is good enough” school of thought, especially when collecting for payment.

The pharmaceutical industry comes in for a huge amount of bad press but at least it has standardised product removed from the vagaries of human error. My elder daughter is a synthetic organic chemist who spent her later university years working on replicating a compound of great potential that had been identified in a plant native to Thailand. I was discussing herbal remedies with her recently and her comment was that, certainly when it came to ingesting a remedy, she’d rather buy it ready-made because then there is more certainty about the accuracy of the source plants and the dosage. For of course the time of the year when plant material is gathered can have a dramatic effect on the concentrations of a desired compound, let alone growing conditions. There will be much greater margin of error when it comes to home-prepared topical applications – in other words applied directly to the skin. But I would be very cautious and want certainty when it comes to swallowing or inhaling.

We are raised in this country to fear most mushrooms and toadstools. The dangers of misidentification can be fatal when it comes to eating them. That caution is not always extended to the plant world. Natural is not a synonym for safe and healthy. If you want wild gathered food skewers, use sticks of a rosemary bush not daphne or, as mentioned last week, oleander.

First published in the Waikato Times and reprinted here with their permission.

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