RUNNING HEAD
32
KEW AUTUMN 2015
W W W. K E W. O R G
In late September a host of literary greats will be descending on the Gardens
for the Write on Kew festival. While plants and gardens have been a source
of peace and inspiration to many, a certain famous murder-mystery novelist
used plants as the ultimate weapon. Kathryn Harkup investigates
PLANTS,
POISONS
and
POIROT
K E W. O R G
KEW AUTUMN 2015
33
Below: Agatha Christie penned
a total of 66 detective and
murder-mystery novels, and
was extremely knowledgeable
about plant poisons, having
worked as a nurse and a
pharmacy dispenser
Right and far right: widely
grown in gardens, the foxglove
(Digitalis), monkshood (Aconitum)
and castor oil plant (Ricinus) –
see seeds on p33 – all contain
poisons used with murderous
intent in Christie’s novels
P
eering over the hedge of a well-tended
garden, a little old lady watches the goings-on
in the village while pretending to do a bit of
weeding. In another garden, some of the
sage plants don’t look quite right. Elsewhere, a sick
woman receives peaches grown in a friend’s hothouse,
but the fruit tastes very bitter. And in London, a funny
little man with magnificent moustaches brushes an
invisible speck of dust from his patent leather shoes.
We can only be in Agatha Christie land.
Dame Agatha, the Queen of Crime, is renowned
for her use of poisons. In fact, she used them more often
than any other method of murder in her hugely popular
novels and short stories. As a teenager reading her
murder mysteries, I loved Hercule Poirot’s pernickety
ways, the gentle humour and the brilliant puzzles Christie
set. Reading Christie as an adult with a background in
chemistry, it’s her use of poisons that now fascinates me.
From atropine to ricin, from belladonna to
strychnine, the number and variety of toxic compounds
she used is staggering. Many of Christie’s chosen
poisons are produced by plants and, in the right dose,
also have applications in medicine. Christie’s training
as a dispenser during the First World War gave her
an excellent knowledge of drugs and poisons. As the
Renaissance scientist Paracelsus, who’s considered to
be the father of medicine, said, ‘The dose makes the
poison’. Christie understood this well and had many
of her characters bumped off with overdoses of
compounds from their own medicine cabinet.
In 4.50 from Paddington, Harold Crackenthorpe
receives a box of pills, ostensibly from his doctor. However,
the murderer has substituted his usual medication for a
lethal dose of aconitine, a compound found in Aconitum,
a beautiful border plant familiar to many gardeners,
also known as monkshood, wolfsbane or devil’s helmet.
Aconitum is considered to be one of the most toxic
plants known. A mere two milligrams of pure aconitine
is enough to kill an adult man, and a few bites of its
roots, sometimes mistaken for wild radish, can bring
about a dramatic and painful end.
34
KEW AUTUMN 2015
Aconitine disrupts the normal function of heart
and nerve cells, resulting in symptoms such as a burning
sensation, said to be ‘like a hot poker is being drawn
across the tongue’, excruciating convulsions and death,
around two to six hours later, due to paralysis of the
heart or the muscles that control breathing. Aconitine
can also be absorbed through the skin, so gardeners
pulling up Aconitum plants should always be careful
and take the precaution of wearing gloves.
Aconitine poisonings, both intentional and
accidental, are thankfully relatively rare, despite the
plant growing both in gardens and in the wild in many
countries. There is greater awareness of the toxicity
of some other familiar plants. Digitalis (foxglove), for
example, is widely known to be both poisonous and also
the source of cardiac drugs. Digitoxin, obtained from
Digitalis purpurea, and digoxin, from Digitalis lanata,
are still prescribed to treat rapid heartbeats. The
compounds slow the nerve signals that co-ordinate the
heartbeat, as well as slowing and intensifying muscle
contractions, leading to more efficient pumping of the
K E W. O R G
L I T E R A RY F E S T I VA L
A is for Arsenic: the poisons of Agatha
Christie by Kathryn Harkup (Bloomsbury
Publishing) is available now, RRP £16.99.
Photos: Pictorial Press Ltd/Alamy, Jacky Parker/Alamy, Premium Stock Photography/Alamy;
p32–33: Bloomsbury Publishing, Tim Gainey/Alamy
Hear more about 14 poisons used in
14 of Christie’s novels at Kathryn’s talk at
Write on Kew on Thursday 24 September.
See details on p77 and book your tickets
now at kew.org/write-on-kew.
blood. Too much though, about ten milligrams, can
stop the heart completely, resulting in rapid death.
Agatha Christie bumped off Mrs Boynton with Digitalis
in Appointment with Death. The murderer was aware of
Mrs Boynton’s heart condition and used digitoxin to
make it look like the old lady had died of natural causes.
Kew has quite a collection of plants whose poisons
feature in Christie’s books. As well as those already
mentioned, there are other classic poisons such as
strychnine, extracted from Strychnos nux-vomica, which
can be found in the Palm House. Strychnine was used
by Christie several times, but perhaps most famously in
her first novel, The Mysterious Affair at Styles. Poppies
remain the source of medical morphine and were used
by Christie to kill in Sad Cypress and several other stories.
Hemlock (used in Five Little Pigs) and angel’s trumpet
(Brugmansia), a source of atropine (used in A Caribbean
Mystery), can both be seen at Kew. So too can Ricinus
communis, the seeds of which are the source of castor oil
as well as ricin, the poison famously used to assassinate
Bulgarian dissident Georgi Markov on Waterloo Bridge in
K E W. O R G
1978, and by Agatha Christie to dispatch several members
of the same household in The House of Lurking Death.
The list of sinister seeds and lethal leaves that
feature in Christie’s work is a long one – I’ve only
scraped the surface here, but I will be revealing lots
more in my talk at Write on Kew on 24 September. Poisons
and plants provided Christie with inspiration for her
plots as well as offering vital clues to her detectives in
their quest to catch the culprit. Read her books, find
the plants at Kew, and certainly think carefully before
you eat anything you’ve picked in the wild!
—
Kathryn Harkup is a science communicator,
former research chemist and author of
A is for Arsenic (see panel above)
—
Book your tickets now for Write on Kew (see p76) to hear
more fascinating tales of the power of plants in literature.
Friends of Kew can get discounts on a range of tickets.
—
Join a free literary tour of Kew on 24–28 September and get a
new perspective on the Gardens. It’s a great way to round off
a visit to the literary festival – see p66 for tour details.
KEW AUTUMN 2015
35