Poisonous Plants and Fungi

Do you know which plants and fungi are poisonous?

The brown hay cap Panaeolina foenisecii is a common mushroom that grows in short grass, such as on lawns. It accounts for most childhood cases of suspected poisoning by fungi, but only causes symptoms if large numbers are eaten.

We can all name a few poisonous plants, and possibly even identify them, but the majority will come as a surprise. Perfectly safe plants may be wrongly considered poisonous; particularly if your child has just eaten some. As for 'mushrooms' and 'toadstools': what is the difference? There is room for us all to increase our knowledge of which plants and fungi are poisonous.

Staff of the Guy's & St Thomas' Information Service collaborate with the Royal Botanic Gardens, Kew, to find new ways to help. The Poisons Information Service knows how important it is for plants and fungi to be identified correctly so that the right treatment can be given

Identification

Several plants have the common name nightshade. Deadly nightshade Atropa belladonna has black fruits that have be mistaken for bilberries although they are much larger. The fruits of the more common woody nightshade turn from green, through orange, to red. Both are poisonous.

In 2000, we published an interactive identification system on CD-ROM: Poisonous Plants and Fungi in Britain and Ireland. It is used by many Accident & Emergency Departments in hospitals around the country, as well as by parents, local authorities, and other interested people. By answering simple questions about the plant or fungus you can make an accurate identification, confirmed by a comprehensive set of photographs. Detailed information about the toxicity of the plant or fungus can then be read and printed, including: poisonous parts; toxins (poisonous chemicals); symptoms; and treatment advice. The CD-ROM, priced at £15.99 (special offer, reduced from £44.95), can be purchased from www.kewbooks.com

Buying a Plant

Many houseplants, such as dumb cane Dieffenbachia belong to the Araceae family and contain calcium oxalate crystals. When chewed, these damage the mouth and throat causing a burning sensation and swelling of the soft tissue. Young children and pets are particularly at risk.

When you go to your local garden centre to choose plants for your house or garden, look carefully at the labels. As well as telling you things like the name of the plant, how big it will grow, and how much sun it likes, you should also see a warning if the plant is poisonous. For example, labels for the common houseplant, Dumb Cane (Dieffenbachia) should say CAUTION toxic if eaten/ skin and eye irritant. Kew and the Poisons Information Service compiled detailed reports on the toxicity of cultivated plants. We worked with the Horticultural Trades Association and the Royal Horticultural Society to produce a list (now available online as a PDF document) of plants that should carry warnings.

Children

The largest group of people at risk from poisonous plants is children under the age of 5. They spend time in homes, gardens, parks, and the countryside with their parents and childcare providers such as childminders, nurseries and grandparents. Our next challenge is to produce an information guide that can be used by all these people to keep children safe. It will provide images, brief descriptive information, and a summary of likely symptoms. Based on our previous work, we are in a good position to: outline which plants pose a potential hazard; help people to assess the risks; and suggest steps to minimise potential harm. This guide is currently being compiled. It will include all the plants in the Horticultural Trades Association code (see above), plus poisonous British plants, giving a total of around 130 plant genera.

Skin reactions

German primula

Type specimen

Skin damage caused by primula

Handling some plants can result in a severe skin reaction. German primula Primula obconica causes an allergic reaction in sensitised people, but allergen-free cultivars have been developed in recent years. Other plants, such as giant hogweed Heracleum mantegazzianum and garden rue Ruta graveolens, cause a phototoxic reaction. Irritation, pain and blisters result from exposure to plant sap in, or followed by, bright sunlight.

Poisoning cases

We would be interested to hear about any recent or old cases of plant poisoning in the United Kingdom, following contact with a plant, or after eating it.

The purpose of this request for information is to improve medical and scientific knowledge about adverse health effects occurring after poisonings by plants, and to assist in the development of better strategies for patient care. We are collecting information on incidents of poisoning caused by any plants (native, introduced, ornamental, etc.) found growing in Britain and Ireland. We are interested in all plant poisoning episodes, whether or not advice or treatment was received from a medical practitioner (GP, Casualty (Accident & Emergency) Department, etc.). In addition, if you know of anyone who has been poisoned please tell them about this web site, or give them a copy of the questionnaire. Please provide as much information as you can. Any information we receive will be treated in total confidence. Please print the questionnaire (Word document) and post it to the address provided at the bottom.

Resources

Acknowledgements

The work on poisonous plants and fungi undertaken jointly by Kew and the Guy's & St Thomas' Poisons Information Service has been made possible by donations and grants. The generous support of the following organisations is gratefully acknowledged:

  • Special Trustees of Guy's Hospital;
  • British Library;
  • Children Nationwide;
  • Kirby Laing Foundation;
  • Trustees of the Royal Botanic Gardens, Kew.

Contact details

If you would like to support this work, and for further information, please contact:

Dr Elizabeth A. Dauncey, Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB

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