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Book Review

'Poisonous Plants: a guide for parents and childcare providers'

A woman once told be how, when she was three years old, her father decided to remove a laburnum tree from the garden to avoid her being poisoned by it. He had just felled the tree when he got called away to the front door. He returned to find his daughter opening another seedpod to get at the ‘peas’ inside it. The woman couldn’t remember any symptoms of poisoning but she did remember the unpleasant experience of having her stomach pumped.  

Hyoscyamus niger, henbane

Hyoscyamus niger, henbane

That story raises three of the most important questions involving children and poison plants. Should you try and remove every poisonous plant from your garden? How should you protect children from exposure to poison plants? And, just how harmful are these plants?  

In ‘Poisonous Plants – A guide for parents and childcare providers’, published by the Royal Botanic Gardens, Kew, Dr Elizabeth Dauncey sets out to answer these and other issues about the plants in our gardens and houses drawing on the known facts about the plants and poisoning incidents.  

Atropa belladonna, deadly nightshade

Atropa belladonna, deadly nightshade

The book is, effectively, in two parts. The first part looks at general matters of how plants cause harm and the harms caused, as well as offering a number of safety tips for preventing accidental exposure and dealing with it if it does occur. The most useful paragraph is headed ‘In perspective’ and points out both that ‘the majority [of plants] are quite safe’ and that ‘More serious harm is extremely rare’. Dr Dauncey points out that the total number of incidences of child poisoning from plants is ‘very small particularly when compared to the number who accidentally eat other poisonous substances such as prescription drugs’.  

She also explains that very young children may well put plant parts to their mouths but mostly just to help detect the nature of the item and that older children, who are still not old enough to understand warnings about plants or have ignored them, are most likely to play at eating rather than ingesting large amounts.  

This very useful and balanced first part finishes by listing some plants which can be grown to encourage children to develop a love of gardens and giving photographs of no or ‘low toxicity’ plants.  

Heracleum mantegazzianum, giant hogweed

Heracleum mantegazzianum, giant hogweed
growing near a shopping centre in Edinburgh

The second part gives a page by page account of 132 plants; 117 of these are the plants which make up the Horticultural Trades Association (HTA) list of potentially harmful plants plus 17 others which, like Conium maculatum, are never sold or are vegetables, like rhubarb, which have some poisonous parts.  

Though a few pages are about one species in a genus which has unique properties most of them look at an entire plant genus. This does mean, for example, that Heracleum sphondyllium, hogweed, and Heracleum mantegazzianum, giant hogweed, are treated in the same way when the actual effects of the latter are a great deal worse than the former.  

Each page has the same headings ‘Family’, ‘Description’, ‘Main toxins’, ‘Risk’, ‘Symptoms’ and ‘HTA category’. The 'Risk' section is likely to be the first concern of anyone worried about a particular plant. The author gives three categories of risk based on the number of annual enquiries made to Guy’s Poisons Unit about human poisoning. ‘Very few’ means no more than four calls, 5-19 counts as ‘Few’ and 20 and over is ‘Many’. The problem is that these are absolute numbers of calls and take no account of how common a particular plant is. Thus, the highly toxic but quite rare Hyoscyamus genus has ‘very few reported cases’ suggesting it poses little risk while the, more frequently seen, Atropa belladonna, which contains very similar toxins, is in the ‘Many’ category.  

The second part of the 'Risk' section gives an indication of how severe poisoning is when it does occur. I suspect that different readers will reach different conclusions based on these two parts. Is a plant which rarely causes severe poisoning more of a concern than a plant which causes mild poisoning but more frequently?

Laburnum

Laburnum in flower

Although the second part of the 'Risk' section gives an idea of the possible harm, it does not indicate how many of the reported cases produce that outcome. In the USA, for example, poinsettia results in a large number of calls to Poison Control Centers but almost no actual poisonings.  Not surprisingly, laburnum is in the ‘Many reported cases’ category but, given the public perception of this beautiful tree as being a serious danger, it would be useful to know how many of the reports involved actual symptoms of poisoning.  

By my reckoning, 95 of the 132 plants described are in the ‘Very few reported cases’ which, hopefully, will give a reassurance to those inclined to panic when they read that such and such a plant is poisonous.  Readers should keep the line from the first part 'More serious harm is extremely rare’ in their mind. 

But, while the descriptions of the effects of the plants and their potential to be harmful left me wanting more, the photographs on each page are a very useful resource. As are the end cover flaps which can be opened to show a key to the symbols used on the plant pages to show which plant part(s) may encourage ingestion, what sort of plant it is and where it is, mostly, found. Taken together, this is a simple, and effective, way to make a positive identification.  

The plants in the second part are grouped together by approximate similarity of appearance which should be helpful to anyone seeking to identify a plant and is a much better way of organising such information than going A to Z. Anyone knowing a plant name is likely to start at the index.  

Dr Dauncey has done a very good job of providing reassurance to people who might be inclined to concrete over their gardens thinking this will eliminate risk and her book is to be preferred to those others which, deliberately or due to incomplete study, overstate the real problems poison plants cause.     

In fact, I’d go so far as to say that it is the second book on poison plants which everyone should have in the home.  

‘Poisonous Plants: a guide for parents and childcare providers’, by Elizabeth A. Dauncey (Kew Publishing 2010) ISBN 978 1 84246 406 9, £15.00, available from www.kewbooks.com