Elizabeth A. Dauncey & Sonny Larsson on Plants That Kill

Have you ever wondered which are the most poisonous plants in the world, why they produce toxins, and what those toxins are? Are you interested in the ingenious ways that humans have found to exploit these plants for good or evil? Plants That Kill, a new, beautifully illustrated, popular science book provides the answers.

Authors Elizabeth A. Dauncey and Sonny Larsson met when they were both working as scientists at the Royal Botanic Gardens, Kew, in London, and have now combined their experience and expertise in the botany and chemistry of poisonous plants and their toxicity to animals to write an informative and engaging book that gives you the facts.

Why did you write the book?

ED: When the chance arose to introduce this fascinating aspect of plants to a worldwide popular science audience, I just couldn’t resist. Plants are essential to the survival and wellbeing of humans and animal life in general and this book is a way of engaging with the public and showing them that plants are interesting. Also, poisonous plants always make a good news story (not a good-news story) and this book was an opportunity to present more fact-based information that is still entertaining. It might dispel a few myths and definitely includes more than a few surprises.

SL: How could I say no to an opportunity to explain how and why plants produce compounds that are poisonous? Its just a great subject! I never cease to be amazed by the sheer variety of chemicals that plants produce and the numerous mechanisms by which they can cause harm. I also think the book provides an opportunity to get people curious about new aspects of the subject regardless of whether one’s particular interest is in plants, poisons or ecology.

Who is this book aimed at?

ED: Anyone interested in how plants or nature works, such as people with an academic or general interest in biology or chemistry, the natural world more broadly or man’s interaction with it. We couldn’t avoid including some rather long names of chemicals and the scientific names of plants, but people shouldn’t be put off by these as the rest of the text has been written to be accessible.

SL: The plants are the focus and center of attention in this book, so it is for anyone curious about how poisonous they can be, or their natural history more widely. I actually think everyone will get something out of reading this book — in the end the subject is a mix of science and human-interest stories.

What makes this book special or different?

ED: Plants That Kill really is one of a kind. Its uniqueness is to bring together in one package a global survey of the most harmful plants (particularly those that have killed humans and other large animals), describing the toxins that they produce and exploring their effects illustrated by interesting cases of poisoning. We’ve chosen to organise the plant toxins, and the plants that contain them, according to the part of the body that they affect most, which is an unusual but useful way of approaching the subject.

SL: I think what sets the book apart is our handling of the chemistry of poisonous plants within a biological framework — you’ll not only learn about the toxin and how it works on the animal body, but for many substances we also give examples of its role within the plant.

How did you decide which plants to include in the book?

SL: The book is intended to present the most poisonous plants from around the world, but there are so many plants that are potentially deadly that finding a fitting selection of actual killers took some deliberation. We didn’t want to restrict the book to only those plants that have killed humans, but broadened the scope to include other animals whose death might evoke at least some sympathy — very few people would miss a mould or a microscopic worm, but they would notice the demise of an elephant.

ED: To draw up our list of potential plant candidates, we consulted books about poisonous plants from around the world and research papers on particular topics such as arrow poisons. From each we picked out the most poisonous ones and then grouped them by the toxins that they produce. The final selection of plants was easy for some, such as the castor oil plant whose seeds contain ricin, a highly toxic plant protein. For others, the toxin group was clearly important but the particular plant or plants to feature was less obvious. Those took more research looking for the deadliest examples and weighing up the evidence to decide which one should be highlighted rather than another.

You’ve included a chapter on medicinal plants, why?

SL: I think it is important to put the concepts of “poisonous plant” and “toxin” into perspective, and giving examples of plants containing really dangerous compounds that we are now using as drugs fighting disease is a very good way of doing that.

ED: In addition to the chapter, we’ve actually included medicinal uses of plant toxins throughout the book. It provides balance to the description of a plant’s toxicity and illustrates how humans have adapted this for their own benefit. Many killer plants really are far more useful to man than dangerous and that’s an important thing to mention.

Did you learn anything new while you were writing Plants That Kill?

SL: So much! Even though I used to teach pharmacognosy and now work at a poison information center, the emphasis has been on local plants and in Sweden we have very few representatives of the really dangerous ones growing in the wild. Reading up on poisonous plants from all over the globe introduced new hazardous substances, species of exotic (at least to me) plant families and stories from cultures far away.

ED: Yes, taking time out to review the latest literature across the board meant that there were plants, toxins and circumstances of poisoning that were completely new to me too. We treated such novelties with the same evidence-based scientific approach to researching that we used for the more familiar plants and toxins, so I’ve learnt a lot during the process of writing, particularly around the chemistry and the mechanisms of toxicity. It was absolutely fascinating and absorbing, which I hope is reflected in the finished book.

Do you have a favorite plant or toxin?

ED: I’d choose a plant family, the carrot family — also known as the Apiaceae or Umbelliferae. Most members of the carrot family can be easily recognised by the structure of their heads of flowers, which form umbels (imagine an umbrella with the canopy formed from clusters of small, usually white, flowers). It gives us root vegetables such as carrots and parsnips, and we happily eat the green parts and seeds of celery and herbs like fennel and coriander. But amongst these wonderful food species lurk some of the most poisonous plants in the world. Examples include dead man’s fingers and hemlock that can kill if a root or leaves are eaten, whilst giant hogweed can cause severe skin reactions if physical contact is combined with bright UV light, such as you might experience on a sunny day.

SL: I am rather partial to colchicine, which is restricted to the autumn crocus family, the Colchicaceae. It has been used as a medicine for gout and a poison since antiquity, and is an important tool in the study of chromosomes and cell division. The fact that it has a very peculiar chemical structure that took over a century to discover also adds to my fascination.

 

Elizabeth Dauncey is a botanist and taxonomist who for the past 25 years has specialised in poisonous and more recently also medicinal plants. She has also written Poisonous Plants: A guide for parents and childcare providers, which provides the information and tools to assess the risk posed by plants in homes, gardens and the countryside.

Sonny Larsson is a pharmacist and pharmacognosist who for almost two decades has studied the connection between plant chemistry and evolution, trying to figure out why and how we can use plants to develop drugs. At the Swedish Poison Information Centre he works as a specialist consultant on plants, herbal drugs and dietary supplements.