THE POISON GARDEN website       Arum maculatum berries on a Cannabis leaf 

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Frequently Asked Questions

Why is that plant trying to kill me?

It isn’t. The idea that the plant has some reason for trying to kill you is the result of the arrogance of the human species.

Until quite recently, the belief was that human beings are not only the most advanced species in the world, they are the reason the world exists. Different cultures have had different theories about the creation of the world and life on earth but they all assume that human beings are at the centre of the creator’s purpose.

From this viewpoint, a plant which harms a human being must be doing it deliberately and a lot of philosophical effort has been put, historically, into trying to determine what the plant’s motivation is.

Theophrastus Phillippus Aureolus Bombastus von Hohenheim (1493-1541), who became known by the single name, Paracelsus, was a Swiss. Depending on the view of his work taken, he is described as a philosopher, aesthete and nutter.

Paracelsus was the first person to say that trying to determine why a plant was trying to poison someone was the wrong approach. Plants contain substances which they need for their life cycle and some of those substances can cause harm to living creatures by combining with a substance which is essential to the creature’s own life cycle.

He also pointed out that the poison is in the dose. In other words, take enough of almost anything and it becomes harmful and, conversely, small amounts of poisons may produce no ill effects.

See also, How Can Birds Eat Poisonous Berries?

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Are Plants Really 'Wicked'?

There's a tendency amongst writers, notably American gardening writers who have turned their attention to poisonous plants, to overstate the threat posed by these plants.

I have one book, written some years ago, where the author states that plants from the Ilex genus, holly, are especially dangerous to children and implies that they should not be brought into the house at Christmas. This, of course, completely ignores the simple fact that millions of people have holly in the house each year and there are no more than one or two instances of mild poisoning in the past one hundred plus years.

This same author states that 'deaths' are on record from eating large quantities of apple seeds. As a result, she says the seeds should be removed from an apple before eating. In fact, there is only one, poorly documented case where death from consuming apple pips is said to have occurred. Almost everyone leaves the core of an apple uneaten and, it could be argued, rooting around with a knife to remove apple seeds could damage the seeds and release toxins which would otherwise go undigested.

Other authors look at the statistics published annually by the American Association of Poison Control Centers and try to make a case that plant poisoning is a frequent occurrence. The latest AAPCC report shows that while there were just under 60,000 calls to poison control centres in 2009, less than 5,000 of those resulted in treatment in a healthcare facility, only 62 were classified as being 'major' poisoning and there were 2 deaths. In total, the report details 1,158 deaths. It's worth noting that one of the two deaths resulted from deliberate ingestion of Datura stramonium, jimsonweed, for intoxication purposes and the plant in the other case was not identified.

There are, therefore, plenty of other ways of getting killed but, it seems, people like to hear about plant poisoning and like to be told that these plants are far more dangerous than they, in fact, are. I suppose that it is more interesting to read about the nasty things plants might do rather than the 20 deaths which everyday household cleaning products caused in 2009. Or the 37 deaths caused by carbon monoxide. 

Of course, the AAPCC report is only concerned with cases of poisoning which are reported to it. This means it excludes all those who die as a result of diseases brought on by alcohol or tobacco and many of those whose death is related to long-term drug use.

In truth, the plants aren't wicked unless we make them so.

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How Can Birds Eat Poisonous Berries?

Simple. It isn’t poisonous to them. See ‘Why is that plant trying to kill me?’ for a detailed explanation of what we actually mean when we call a plant poisonous.

If a creature doesn’t have a substance which will combine with the ‘poison’ in the plant, then that ‘poison’ will have no effect on that creature.

Poisons, generally, work in one of two ways. They combine with a substance which is essential to a creature’s life creating a third substance which is excreted. It is the removal of the essential substance which results in the harm. Or, the substance created by the reaction of the ‘poison’ with the substance in the creature is itself harmful to the creature.

The best example of the different effect a plant has on different creatures is the Conium maculatum, poison hemlock. The principal active ingredient in poison hemlock is called coniine. For humans it can be a deadly poison working on the peripheral nervous system. That is to say it numbs the extremities first, the fingers and toes, and the numbness creeps into the body eventually reaching the chest and paralysing the lungs. Death results from asphyxiation but the mind remains unaffected so the victim is aware of the creeping numbness bringing death to them.

Birds are completely unaffected by coniine. They actually do nothing with the substance and, as a result, it builds up in the flesh without causing them any ill effect. This means the coniine is still available to poison a human being if they consume the flesh of the bird. In a twenty year period in Italy, where wild birds are often trapped or shot as they migrate south, there were seventeen cases of hemlock poisoning resulting from the eating of wild birds. Four resulted in death and, in one case, the bird had been in a freezer for three months but the coniine was still active.

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How Many People Die Because of Poison Plants?

That depends on what is meant by ‘because of poison plants’. If the question is how many die from accidental ingestion of plant material, such as eating berries from a poisonous plant, then the answer is very few indeed. There are three reasons for this low mortality rate even though all these very dangerous plants are all around us.

First, the majority of poisonous plants are emetic; eat a large amount and you are likely to suffer violent vomiting which removes the poison from the stomach before it has the chance to do a great deal of harm. One example will serve to illustrate the point.

A middle aged couple had visited an elderly aunt who had prepared a meal for them. The aunt kept her fresh vegetables in a basket on a shelf in her outer kitchen under a shelf housing spring bulbs waiting to be planted. Unnoticed some daffodil bulbs had dropped into the vegetables and the aunt had used them, instead of onions, to prepare the meal.

The husband consumed a whole bulb and the wife half of a bulb. Within ten minutes the husband suffered violent vomiting but felt better immediately after. It was an hour later before the wife was sick and she then suffered vomiting and diarrhoea for two days. So, the husband benefited from the emetic effect of a large dose whereas the wife suffered the symptoms normally described as resulting from ingestion of spring bulbs.

The second important factor in keeping accidental deaths from plant poisoning at such a low level is appearance. For a plant to be eaten, there has to be something about it that makes it attractive to the eye. So, for example, the Rumex obtusifolius, broad-leaved dock, is poisonous but, for humans, it has nothing about its look that would encourage consumption. 

Even if you were tempted to try eating dock, you would come across the third barrier to accidental poisoning; taste. The overwhelming majority of poison plants are unpleasant to the taste. The Solanum dulcamara, woody nightshade, has a very attractive red berry but its taste is extremely bitter. Anyone picking a few from a hedgerow would be unlikely to swallow much plant material as soon as they experienced the bitter taste.

The bright orange berries of Arum maculatum, cuckoopint or lords and ladies, have an acrid taste and, because the poison is in the form of needle sharp oxalate crystals, the mouth and throat very soon begin to tingle from the irritation caused. So, a child coming across the plant in the woods and deciding to try the berries would very soon find the taste unacceptable and not eat above a couple and then, when the mouth or throat began to tingle from the irritation, would rush to seek assistance allowing serious harm to be avoided.

In Europe as a whole, the number of deaths from ingestion of a poisonous plant is so small that no separate statistics are collected. In the USA, less than five people a year die as a result of eating a poison plant.

Evidence that poison plants cause far less harm than might be expected can be found in 'Accidental poisoning deaths in British children 1958-77' published by the British Medical Journal. Neil C Fraser reports on a total of 598 poisoning deaths of children under 10 years of age. In the period covered only three deaths were attributed to plants. Even this low number is overstated since one death was due to fungi and in one of the other two 'the role of ingestion in the child's demise is doubtful'. Thus there may have been only one confirmed plant death, with 'hemlock' being the plant responsible, in twenty years. Fraser's analysis makes it clear that medication, household cleaning materials and cosmetics pose a much higher risk than poison plants.

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So, the plants don’t cause many deaths?

Actually, they do, millions of deaths every year, in fact. Actually, what they do is bring deaths closer. It is true to say that poisons never resulted in a death that wasn't going to happen at some point. What happens is that death is brought forward; these substances shorten lives.

The large number of shortened lives are not caused by plants in their natural state. The huge numbers of premature deaths occur once we start to make products from the plants.

These may be 'natural' remedies which contain a poisonous plant extract. The best example of this is remedies used in traditional Chinese medicine which contain aristolochic acid from plants in the Aristolochia genus. See the Aristolochia clematitis page for full details of the harm this plant does.

Then there are the substances produced because of the effects they have on the human brain.  In Europe, over seven thousand people die from an overdose of heroin every year, estimates for alcohol-related deaths range from one to two million a year and, around the world, over five million die from smoking related diseases.

One key message of The Poison Garden website is that the plants aren’t ‘wicked’. We make them harmful by the ways in which we use them.

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I Have Children - Should I Clear my Garden Out?

As we become increasingly risk averse, people are more inclined to think that they should try and remove all the poisonous plants from their gardens. This ignores the fact that many poisonous plants are found in the wild or on public land, like parks and street plant displays, and that almost any plant can be harmful if you have enough of it.

Sadly, this idea of clearing everything out is, often, put forward in books on poison plants and, increasingly, on websites written by people who don't think through the advice being given.

For a realistic view of the situation regarding plants and children, I recommend 'Poisonous Plants: a guide for parents and childcare providers' by Elizabeth Dauncey.

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Is Cannabis Addictive?

No. It is important to distinguish between addiction and dependency.

An addictive substance is usually characterised by two things; a need for increasing amounts in order to experience the same effects and evidence of physical symptoms if the substance is suddenly withdrawn. A third is sometimes included which is the creation of a craving for the substance but, in effect, this is the beginning of withdrawal symptoms.

Dependency is when there are psychological effects from the absence of the substance. There are, undoubtedly, people who become dependant on cannabis because they feel uncomfortable and stressed if they do not have their usual supply of the substance but even those who might be considered to be highly dependant are not completely controlled by the substance in the way that an alcoholic or heroin 'addict' is.

Anyone who has ever known an alcoholic knows that they have to have a drink whenever they crave it whether that is first thing in the morning or during working hours. Cannabis does not create the same irresistible need.

In its 2006 annual report, the United Nations Office on Drugs and Crime (UNODC) says that ‘many daily users have rules around when and where they will consume, generally restraining their use to leisure time. Surveys of users in New Zealand show 95 per cent of smokers polled said they never used the substance at the workplace……A study of users in Amsterdam, where the drug is widely tolerated, found that declining to consume at work was the single most commonly followed ‘rule’ around consumption, and that 27 per cent of their sample of experienced users adhered to this rule, while a further 20 per cent abstained from smoking during the day, and 15 per cent abstained during the morning’.

People who are addicted don’t make the ‘rules’ about how to indulge their addiction, the addiction does that for them.

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Does Cannabis Lead to Other Drugs?

There are studies which show that a high proportion of addicted drug users began by using cannabis and this is used to argue that cannabis leads on to more harmful drugs. The problem with that argument is that it may be an example of the principle of post hoc ergo proptor hoc, a later event happened because of an earlier event, whereas there is no evidence for a causal link. What we cannot know is how many of those people would have become drug addicts even if there were no such thing as cannabis.

The United Nations Office for Drugs and Crime puts forward another view. In its 2006 World Drugs Report it quotes research which ‘concludes that associations between early cannabis use and later drug use and abuse/dependence cannot solely be explained by common predisposing genetic or shared environmental factors. [The research] argue[s] that association may arise from the effects of the peer and social context within which cannabis is used and obtained. In particular, early access to and use of cannabis may reduce perceived barriers against the use of other illegal drugs and provide access to these drugs.’

In other words, because cannabis is illegal people who use it become acquainted with a criminal world in which ‘harder’ drugs are also available and lose their inhibitions about buying illegal substances.

My own view is that telling lies about cannabis may be the mechanism which makes it a ‘gateway’ drug. If young people are told that cannabis is extremely harmful and that use will lead to idleness, aggressiveness and mental health problems they are highly likely to find their own experience of it to be markedly different. If they are now told that heroin is an addictive substance which leads to many deaths each year due to overdose, they may look at the situation regarding cannabis where they were lied to about its effects and assume that what is being said about heroin, or any of the other ‘hard’ drugs, is also lies.

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Are any of the poisons undetectable?

No, not today. Modern forensic science, if properly used, can detect even the tiniest amount of any poison.

But that isn’t the question you wanted to ask.

Is it possible to get away with murder?

That’s more to the point. Because that is a very different question. Given that these poisons can be detected even in the smallest amounts, the way to get away with murder is to not have anyone look for the poisons. In other words, if no-one suspects murder took place, no-one will go looking for any poisons.

We pay much more attention to death than we used to so it is less likely that unexpected deaths won’t get fully investigated but investigation is by no means certain. Harold Shipman had a twenty five year career of murdering patients with an overdose of morphine but, for most of that time, no-one suspected murder was taking place.

In the past, when death was less likely to be closely examined, getting away with murder was much easier. Take, for example, strychnine derived from the Strychnos nux-vomica plant. During Victorian times it was a major component of rat poison and, with inner city areas being rat infested, rat poison was easy to buy with no questions asked. Strychnine has a bitter taste but, if you put it in something expected to be bitter, you can disguise the taste. As soon as your victim says ‘This tastes funny’ you’ve lost the chance of murder not being suspected.

Strychnine is a stimulant, making the muscles contract uncontrollably. Death is often the result of exhaustion but the contractions also lead to the muscles pulling themselves away from the bones allowing the body to contort into normally impossible positions. These contortions and convulsions are called ‘tetanic’ because they look very like the death throws of tetanus, which was endemic in Victorian slums.

So, strychnine was easily obtained and no-one would notice the murderer had purchased it, the taste could be disguised so the victim wouldn’t suspect anything and the death would be attributed to tetanus.

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