The call went out to UK gardeners for yew clippings. Yew snowman from Helmingham Hall

I keep waging war on what I see as very sloppy thinking and pseudo science. The sort of thinking that says natural = good, chemical = bad, synthetic = even worse, modern medicine = corrupt multi national pharmaceutical hijack, herbalism and natural medicines = healthy alternatives. Often there’s a sort of Luddite sentimentality, a belief that the wise women and healers of long ago knew better.

Ahem. Life expectancy was much shorter, by decades in fact. And for every natural plant-based cure that worked, there were probably many more that didn’t. Poisonings went unrecorded, as did misidentification of plants. Medical misadventure was not exactly a matter of record.

The binomial plant naming system devised by Linnaeus in the mid 1700s has stood the test of time, though it is now under siege from the dumb-it-down brigade of Make Gardening Easy persuasion. Linnaeus’s plant classification system was incredibly important when it came to medicine. Until that time, there was no standard identification, naming and recording system for plants. Doctors and healers were often at the mercy of those who went out collecting the wild plants, many of whom would have had little idea of what they were harvesting. The same plant could be given many different names and vice versa – the same name could be applied to many different plants. It still happens.

Marigolds. But which one?

Take marigolds. Yes do take them. They are not my favourite plant at all. But how many readers understand the difference between calendulas and tagetes? They are entirely different plant families and we commonly refer to both as marigolds. Both are used quite extensively for their natural compounds but they are not interchangeable. If anybody is going to treat me either internally or externally with marigold extracts, I would like to think they know the difference between, for example, Calendula officinalis and Tagetes minuta, let along the various other plants entirely which are often referred to as marsh marigolds, corn marigolds or marigolds of various other persuasions. I prefer my medicine a little more exact and for that, I thank Linnaeus.

A large proportion of modern pharmaceuticals continue to be derived from plants. Aspirin originated from willow. Much work has been done on the cancer fighting properties of yew. Valerian has long been recognised for its special properties – but false valerian is a different plant family altogether.

The yew is an interesting case study for those who think synthetic copies are all bad. In the early days of cancer research into the curative properties of taxus, British gardeners were encouraged to gather all their trimmings when they clipped their yew hedges and topiary and to deliver them to collection points. If you had sufficient volume of high quality trimmings, you could even get paid for it. They responded with enthusiasm but it took an awful lot of yew trimmings to yield a very small amount of the relevant compounds used in chemotherapy. Even more problematic was the one which derived from the bark of the Pacific yew (Taxus brevifolia). You cannot continually harvest tree bark in large quantities. Clearly it would never be viable unless the researchers were able to reproduce the compounds efficiently in a laboratory. It is called synthetic organic chemistry because it is about reproducing a natural compound by synthesis. I know a small amount about this on account of having a daughter study it to a very advanced level (by which I mean post doctoral fellowship, working as part of a team isolating the active ingredients from a Thai plant with huge potential). It is not all bad. In some cases it may save the natural environment, not having to harvest huge volumes of natural products. It can even out seasonal and geographic variations in the strength of active compounds in plants. It can certainly deal to the problems of misidentification.

Most of our poisons are also plant-based. Many people know about laburnum seeds. Fewer realise the toxicity of daphne seeds. Cyanide has its origin as a plant product. So indeed does strychnine. Euphorbias exude a sticky sap which is renowned as a skin irritant. Rhus trees are problematic – so much so that after one bad encounter with some sawdust while chainsawing a fallen branch, Mark refuses to approach our rhus tree without donning protective gear similar to a beekeeper. Derris dust is seen as natural and organic – and it is because it comes from roots of certain plants but that doesn’t make it safe. Rotenone (which is sold as Derris dust) is linked to Parkinson’s Disease and is very toxic indeed.

It is a dangerous natural world out there. It’s a miracle we gardeners survive really. Which is why I am deeply suspicious of ill-informed enthusiasts rushing out to promote the use of plant remedies on the grounds that they are natural and therefore safer. A little bit of knowledge is a dangerous thing. Until herbalists and natural healers are as strong on botany and chemistry as they are on traditional “wisdom”, I will err on the side of caution.

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