Do you have a poisonous plant in your school garden?

4 August 2012 · 3 comments

in Developing School Grounds & Outdoor Spaces, Gardening, Interesting Issues & Hot Topics, Whole School

During my holidays I visited the Poison Garden at Alnwick Castle. This garden was established in 2005 as an entertaining yet educational opportunity for the public to learn more about herbs and plants which have potentially dire, and sometimes fatal consequences, when humans come into contact with them.

Alnwick Poison Garden

The Garden is an interesting place in that the plants selected for inclusion are a good mix of the well-known plants such as deadly nightshade (Atropa belladonna), famous “phantastica” plants including tobacco (Nicotiana sylvestris), the heroin poppy (Papaver somniferum) and the coca plant (Erythroxylum coca) and then more ordinary plants which one might have growing in any garden that have some potentially hazardous effects. The plants in the cages are either illegal to grow or highly poisonous. The Home Office has given Alnwick Garden a licence to grow cannabis (Cannabis sativa) and coca.

What interested me was this choice of plants in the garden. Perhaps the best part of the tour was seeing ordinary everyday plants in the Poison Garden amidst the ones which are more notorious. For example at the entrance to the garden is a patch of nettles (Urtica dioica) and dock leaves (Rumex obtusifolius). Elsewhere a patch of catmint (Nepeta faassenii) was growing. One of the key features of the garden is to encourage people to question and challenge things that they are inclined to take for granted.

Nettle has been included as it will sting you if you brush past its leaves, even though it has a high wildlife value. Dock leaves contain organic oxalates which can lead to calcium deficiency and to the build up of kidney stones, yet these same leaves are used to relief the pain of a nettle sting. So whilst one the one hand it’s a cure, it is not so good to eat large quantities of of the tough-looking leaves. Anyhow, it tastes very sour and unpalatable. Catmint is renowned for its effect on cats more than humans!

The inclusion of the plants that produce illegal drugs is a definite hook. My teenage son was with me and to be able to see these plants and hear the guide talk about the financial, social and health impact of these cash crops on the growers as well as the users definitely held his attention. It also helps in terms of what a drug actually is and looking at the folklore around different plants, their effects humans and how they have been used both for good and for bad reasons.

Years ago, I was seconded to deliver drug education training for teachers. One of the activities we used to undertake was getting teachers to look at information cards about different drugs and then agree as a group how to rank the drugs in terms of harm from “most” to “least” harmful. It creates interesting discussions and has a lot in common with current debates in the education sector about managing risk.

John Robertson, the first Warden at the Poison Garden makes a very apt statement in defence of plants that can cause harm…

“Harmful is a very significant word when it comes to poison plants. A plant can be as poisonous as it likes but, if there is nothing about it that encourages you to engage with the poison, it can never be harmful.”

John has set up a well-organised and accessible website called The Poison Garden and wrote a book about the experience called Is That Cat Dead? Whilst health protection officers, politicians and police drugs experts may niggle over some of his comments and perspectives (this is normal – every professional has a different viewpoint, in my experience), he does offer interesting insights. For example, he suggests that much of the folklore that has grown up around plants is from stories parents would tell their children, not simply to send them to sleep at night but to remind them to keep away from harmful plants. After reading his book and rummaging around his website, I have to say that both provide a lot of reassurance for educators around the myriad of potentially harmful plants. There’s also good references to stories and historical information around each plant listed and numerous topical blog posts.

The number of fatalities through the ingestion of plant material is so small that it is barely worth mentioning. No children seem to have died for many years which suggests that concerns about children eating  poisonous plants is over rated. A discussion about the Swiss study and accidental plant poisoning statistics can be found on The Poison Garden website which includes a breakdown of the numbers of plants which have caused severe poisoning and statistics from the USA which suggest that only 0.1% of calls to Poison Control Centres have been about severe cases of poisoning and 2% for moderate cases. This amounts to five adult deaths per year and it is not clear whether this is mistaken identity or self-administration for a psychoactive effect.

What did interest me, is that most cases of accidental poisoning happen when someone goes out to their garden and mistakenly gathers or harvests part of plant which is toxic. John Robertson gives two examples. One is about a couple of incidents (bearing in mind the millions of homes in the world which have daffodils) where people have lifted daffodil bulbs out of the ground, thinking they were onions and cooked and ate them. Given that I have daffodils growing in the same raised bed as Welsh onions, I can understand this confusion. Another example came from a visitor who who said, as a child, she had accidentally eaten laburnum seeds because she was eating raw peas from a garden and thought the laburnum seed pods were just a different sort of pea. Common sense thus says, be careful what plants can be mixed up and keep these plants clearly separated and possibly even labelled.

The whole concept of a poisonous plant needs careful thought too. It’s an ambiguous label which can lead to confusion. So much depends on the tolerance of a person or animal to a toxic chemical, the strength and quantity of the chemical (which can be affected by the time of year or maturity of a plant), the level of harm caused by ingestion or use, the numbers of people affected each year, etc. What is in no doubt, is that the tobacco plant causes the greatest number of deaths through its production and use than any other plant. Interestingly, the Poison Garden at Alnwick does not contain any plants that are currently used as the basis of alcoholic drinks such as hops or grains.

For schools and childcare organisations, there are many sources of reference about plants. The Royal Horticultural Society have a free download, Potentially Harmful Garden Plants but it is simply a list with little additional information. Interestingly, the only plant that gets the A-rating here is Poison Ivy (Rhus radicans) which is rarely grown in the UK though prevalent throughout North America. I find this quite bizarre and it makes me wonder if there is a political bias to this list and decisions about what category each plant was put in and why. Hmm… This means educators need to think a little more around the matter.

Firstly, using and giving reference to the botanical names of the plants is a good habit to develop. One of the confusing aspects of local plant names is that different places give rise to various names. The botanical names are consistent and it helps with the taxonomy process. It also means that if someone raises a concern about a plant, you can both be sure you are talking about the same species.

Second, there is no need to assume that these plants should be banned from a school grounds or immediately removed. The RHS recommends

“restricting access to the potentially most harmful plants by care in choice of plants and planting positions in gardens.”

So common sense suggests that plants which cause a reaction when they come into contact with skin need to be at the back of borders and away from places where incidental or accidental contact can happen. If footballs are being constantly retrieved from thorny areas or patches of nettles, then the activity or the plants need to be put elsewhere. Planting edible peas and beans close to a laburnum tree is not sensible as the pods could be confusing.

There is a good argument for educators to develop their own confidence at plant identification and knowledge. The more we know and understand about plants, then the greater our ability to make rational decisions about them in relation to our work with children. It is also a sensible approach with children in that they learn not to eat plants that they cannot accurately identify.

Most potentially harmful plants do not entice people to eat them. Many taste unpalatable, so are likely to be spat out. Many cause vomiting if ingested. Seeds which have the potential to cause harm are often encased in a shell and may pass through the body without dire consequences. A good example here are tomato seeds or apple seeds.

Also there are many potentially harmful plants all over the place. In the garden of my first childhood house grew a whole host of plants including foxgloves, nettles and various berry producing shrubs amidst the daffodils, snowdrops, rose bushes and a rambling crab apple tree grew beside and over the front door. All these plants pose risks of one sort or another. Whether it’s thorns, stinging leaves, fruit that causes stomach ache or simply that the whole plant is poisonous, I grew up living with these plants around us. I bet a lot of you did too! I also remember having discussions with my mother about what plants were okay to touch and which were not. Education seems to be the key rather than trying to rid potentially harmful plants from our children’s lives.

A good authoritative guide written specifically for parents and childcare providers is Elizabeth Dauncey’s Poisonous Plants. It is helpful in that it looks at the number of enquiries received by Guy’s Poison’s Unit and the potential to cause harm. The book also contains straightforward advice about gardening, first aid and emergency advice and a quick identification chart for fruiting plants of low toxicity.

So in response to my title question, the answer is quite likely to be “yes”!

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{ 2 comments… read them below or add one }

Jo May 25, 2017 at 05:39

I agree health and safety can seem to be too stringent at times, but overall when there are large child groups it’s good to be alert. As with all these things it’s not until ‘your own child’ something happens to, you may become more aware. I think the poison garden is great. I think it’s educational. Children would not be allowed to run freely here and the dangers of touching etc would be well advised and warned.
It’s knowing the dangers… you would not plant giant hogweed in a school playing area. Common sense is obviously needed on most things. And personally researching the pros and cons on what you plan to do, not just following what someone else has said ‘seems like a good idea’.


Juliet Robertson May 25, 2017 at 05:49

Thanks for your comment Jo

I do agree – each school is different and it is about common sense and preparation. What we do need is ways of teaching children in calm ways which they understand.

I’ll never forget seeing one of my nephews at 18months being able to identify nettles and blackberry plants and knowing not to touch either 🙂


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