You may even be surprised to find a section on a website about “Growing and Using Herbs” introducing you the idea that some herbs are POISONOUS!

Every garden centre you visit, indeed, every garden you see, contain many such plants!

However, it is important to be aware that some plants can cause harm and in this section I will try to explain why some herbs are toxic and how we should treat them. If youwould like more information, the following useful paperback will introduce you to the potential perils maybe even in your own garden! : Poisonous Plants: A Guide for Parents & Childcare Providers   25 May 2010  by Elizabeth A. Dauncey

Herbs in their natural state, looking decorative in your garden, are unlikely to cause you many problems.  Some do cause minor irritation to the skin or even allergies, but nothing too serious.

I have based the plants I list here on noticing their presence in many nurseries and garden centres.  Additionally, they are listed in books about herbs.  There is additional information on this site which can be found in the links listed below.


Think for a minute why we use herbs?

It’s all to do with their flavour or their aroma. Flavour and aroma produced by herbs is simply there because of various chemicals each plant manufactures.

We may consider plants to be simple living organisms, but each can be regarded as much a minature chemical factory. Plants can produce novel chemicals which cannot be easily synthesised elsewhere. These chemicals can be incredibly valuable to humans or equally, potentially dangerous.

So first of all some SIMPLE chemistry.

I am assuming that you know that all green plants are magical energy converters, transforming sunlight energy into chemical energy stored in sugars and other molecules. This happens during a process of PHOTOSYNTHESIS.

But their cellular chemical factories are truly, utterly amazing. Let’s face it, plants live a simple life. Their main aim is much like ours : SURVIVAL

PLANTS have two things in mind (well not really in mind!!) : REPRODUCTION AND TO AVOID BEING KILLED. Not much different to many humans really.

However, they don’t have the same options as animals have, of course. They cannot get up and run away so they have to hit hard if attacked.  If by some chance one plant has a better chance of reproducing and forming seeds, which then are able to grow into new plants compared with another plant does …. Its chance of survival is better.

AND if you were a plant and you had some tricks up your sleeve to stop animals eating you for lunch, by teaching them a lesson and making them ill … well you are much more likely to live to reproduce anyway …

The plants / herbs we see in the wild, and often in our gardens are the ones who HAVE SURVIVED.  It is by chance that their very survival mechanism makes them highly useful to humans in so many different ways.  But some of these plants also cause our human body problems.

Below is a list of plants that you often find in herb gardens and indeed, garden centres,  which you need to be cautious about. Some of their effects are associated with strange tales which have become FOLKLORE.

Monkshood or Aconite

European monkshood, tiger’s bane, dog’s bane. Many other names associated with its helmet shaped flower such as soldier’s helmet, old wife’s hood.

IN some places it was called Mousebane supposedly due to the number of mice found dead near it!  and is known by some as wolfsbane, because its poison is so toxic that it was once used to kill wolves.

Artemesia or Wormwood

This strong smelling decorative, feathery leaved plant is a herb that should NEVER be consumed.  It is an  ingredient in many

Side effects from consumption of wormwood include renal failure, convulsions, involuntary evacuations, abnormal respiration, and foaming at the mouth though it is argued that these effects are seen only as a result of consuming oil of wormwood.

In the 19th century, people were believed to become addicted to absinthe and some doctors described a condition which they called ‘absinthe epilepsy’.

CAMELIA SINENSIS or in more familiar language : TEA

How Poisonous, How Harmful?

Tea contains both caffeine and tannins.  Caffeine is very addictive. It may surprise you to know that five cups a day are said to be sufficient to produce addiction. Withdrawal or reduced usage after excessive consumption leads to dizziness, headaches, constipation, indigestion, palpitations and insomnia.  My own addiction to caffeine at University in an effort to stay awake when revising for exams was exposed as soon as I finished my exams.  Withdrawl was not a nice experience.

Of course, it’s not just the TEA PLANT to ‘blame’ here. Caffeine is a chemical produced by a number of plants : Coffee beans come from the plant Cofea Arabica and of course CHOCOLATE comes from cocoa (cacao) beans produced by the Theobroma cacao plant!


Much admired for its beauty when in flower, delphiniums have caused a number of fatal poisonings in cattle. Delphinium is a genus of about 300 species of beautiful perennial flowering plants in the family Ranunculaceae

The toxic chemical it produces is called aconitine and eating it leads to nausea, vomiting, abdominal pain, muscular spasms.

Digitalis spp., Foxgloves

Foxgloves are very common plants, found both in garden and the wild. They are sold widely at garden centres and nurseries. They produce a chemical called Digoxin which has very specific effects on human and animals. It increases Cardiac Output but slows the Heart rate so is used in medicine as a cardio-active (heart) drug.

People who eat any part of the plant or make tea from the leaves are, in essence, taking an unregulated dose of heart medicine. This can cause the heart rate to slow down or become irregular. Both can be dangerous and life threatening.

Its use in the treatment of those with heart failure particularly, has saved millions of lives.  However, it has the potential to kill in quite small amounts.  Foxglove is one of many reasons to watch children closely when they play outdoors.  It has unusual flowers which invites little fingers to play with.