Gardens: Beware the poison plant

‘Double, double toil and trouble; Fire burn and cauldron bubble . . .”

When a hapless Irish chef inadvertently poisoned his wealthy employers back in the late 18th century, it was as an unfortunate result of mistaking the leaves of one commonly grown shrubby evergreen (the cherry laurel, whose foliage is naturally rich in the poison cyanide) for those of another – the culinary or bay laurel (Laurus nobilis). But then again, perhaps it wasn't accidental. History tells us that humankind has long used plants for their poisonous properties.An example is the death of the ancient Greek philosopher Socrates, who was executed by means of a deadly draught containing poison hemlock (Conium maculatum), a wild biennial plant commonly found growing along Irish roadsides, hedgerows, ditches and river-banks.

More recently, the deadly toxin known as ricin (the KGB's poison of choice) has been in the news, after an actress attempted to use it to assassinate America's President Obama. The fact that the poison is a derivative of Ricinus communis, the ornamental castor oil plant often used in summer bedding schemes for its decorative foliage, might come as a shock to some.

Their poisonous qualities aside, humankind has also long valued plants for their narcotic, hallucinogenic or psychedelic properties, often putting them to ritualistic use. Vikings, for example, added the seeds of the common weed known as henbane to their drink, which gave it a powerful psychotropic or mood-altering effect, creating what’s been described as “a state of divine madness” and making the warriors go crazy in battle.

Plants also feature heavily in the world of alchemy and the occult. Poison hemlock, the very same plant that killed Socrates, pops up in Shakespeare's Macbeth, this time as part of the magical potion or "hell broth" brewed by the three witches.

In this case, “Root of hemlock digg’d i’ the dark” was just one of several potentially deadly plants that Shakespeare’s witches added into their magical brew of “eye of newt and toe of frog, wool of bat and tongue of dog”. Another ingredient was the leaf of the evergreen yew, a native Irish plant commonly seen growing in our gardens, parklands and churchyards where it’s cultivated as a specimen tree or as a handsome evergreen hedge.

“Tooth of wolf” also went into the witches’ cauldron, a reference to Aconitum, a very decorative but highly poisonous late-summer flowering perennial that can be found growing in the poshest of Irish herbaceous borders. Commonly known as monkshood or wolf’s bane, consumption of this plant’s leaves quickly leads to heart failure and death, making it the poison of choice in Roman times.

No doubt Shakespeare’s witches also used these three plants to make “flying ointment”. Poison hemlock, yew and monkshood all feature in old recipes for this magical salve, which was reputedly used by witches to make their brooms fly.

They are just three of a host of plants with poisonous or hallucinogenic qualities that can be found growing in Irish gardens or in the wild.

Others include hellebores, the autumn crocus, Brugmansia (formerly known as Datura), the opium poppy, Coleus, Laburnum, deadly nightshade, wormwood, the Californian poppy, Nicotiana, Narcissus, Acorus, Kalmia, Actaea, Robinia, Veratrum, Helenium, Ornithogalum, common valerian, foxgloves, Solanum, species of Prunus, lily of the valley, lobelia, mistletoe, rhubarb (the leaves), Arisaema, Dicentra, Daphne, Pittosporum, privet, Irish ivy, many mushrooms . . . the list is too long to give here in its entirety.

Which is not, for one moment, to suggest that we shouldn’t grow them. Stop growing potatoes (a member of the Solanaceae family that contains many plants with associations with the occult/ magic/ shamanism), because their seedheads are highly poisonous?

Refuse to grow daffodils, on the off-chance that someone might mistake the poisonous bulbs for onions? Ban mistletoe, just in case we’re tempted to consume one of its poisonous berries? Hmmm, I don’t think so.

Instead, we need to teach ourselves and others (especially children) to respect the many remarkable – if sometimes poisonous, narcotic, or hallucinogenic – properties of plants. Many of these plants are poisonous only when consumed in large quantities.

In smaller doses, they have valuable medicinal or therapeutic qualities, a fact borne out by the World Health Organisation's estimate that 25 per cent of modern medicines contain plant derivatives. Classic examples include the opium poppy (Papaver somniferum) and the cannabis plant (Cannabis sativa), both famed for their pain-relieving qualities. Others include the humble foxglove, which yields the heart drug known as digitalin, and deadly nightshade (Atropa belladonna), an extract of which is used to treat eye diseases as well as offering, ironically, an antidote to opium poisoning.

All are proof of the remarkable natural pharmacopoeia that is the plant kingdom. My conclusion? Instead of being fearful of it, let’s celebrate it.

Oíche shamna shona duit.