I recently discovered the existence of Alnwick Castle and The Poison Garden. Needless to say it is now on my top ten list of places to go.

Behind locked gates the garden houses a collection of rare and not so rare plants which are deadly toxic. When I first read about it two things struck me. Firstly, what a brilliant idea. Kids in particular are bound to love this and the ghoulish tales that no doubt accompany it. My second thought was how many poisonous plants inhabit our gardens, public spaces and parks and how little I knew about the subject.

I spend so much of my time researching the healing properties of plants it never occurred to me to concentrate on the dangerous and poisonous ones too. After reading about The Poison Garden I began to study which plants are considered most hazardous. I was already aware of the obvious plants like Hemlock, Foxglove, Monks Hood and Henbane but I was shocked how many common plants can be equally dangerous.

ButtercupThe most innocuous wild flowers are often lethal, such as the humble Buttercup which many of us picked as children, waving the flowers under our chins to check if we liked butter. Like other members of the Ranunculus family, Buttercup contains poisonous protoanemonine which is also a strong irritant. Externally this substance can cause blisters; taken internally it ulcerates the throat and digestive tract. If untreated, Buttercup poisoning can progress to internal cramps, kidney inflammation and, in serious cases, death.

Another potentially deadly wild flower is the Corn Cockle, which was once a common sight in grain fields but has largely been eradicated by modern farming methods. I have grown this now relatively rare flower in my garden blissfully unaware of the sinister secrets within. The seeds of the flower are lethal in a large enough dose, creating abdominal pain and diarrhoea. In serious cases the saponin glycoside githagin contained in the seeds affects the central nervous system, eventually causing cardiac arrest. It is easy to see why farmers have been so keen to remove it from their crops.

ColumbineIn gardens, popular flowers harbour similar dangers. Columbine and the rest of the Aquilegia tribe are known to contain substances which can cause heart failure. Euphorbias are another common garden plant – all are toxic but Cypress Spurge is perhaps the most dangerous. The milk of the entire genus is blistering to the skin but Cyprus Spurge can actually permanently damage to the eyesight if accidentally rubbed into the eye. If ingested it can cause terrific abdominal pain, affect the circulation and eventually lead to delirium and collapse. If not treated quickly it can cause permanent damage or even result in death.

Rhododendrons are familiar ornamental bushes found in gardens and public places. I remember picking the massive flowers regularly when I was small, completely oblivious to the dangers. Rhododendron poisoning is thankfully rare but documented cases report vomiting and severe low blood pressure as well as cardiac irregularities. The plant’s poison is so toxic that honey from bees who have fed on the flowers is considered too dangerous for human consumption.

Laburnum Golden Rain TreeAnother ornamental species, Common Laburnum, often known as the Golden Rain Tree, sports vibrant yellow drooping flower which hide deadly fruit. The seeds are extremely toxic causing dilated pupils, hallucinations, cold sweats and vomiting. Within an hour of eating the seeds the person is likely to have expired.

Privet has pretty flowers in the summer months with a lovely scent, and Privet bushes edge gardens and parks the length and breadth of the country. But both privet leaves and berries contain the highly toxic syringin. Ingesting it results in nausea and nervous agitation and without medical intervention Privet poisoning can also be deadly.

An equally familiar hedging bush, Cherry Laurel, is just as hazardous; even a small quantity of berries can cause a feeling of suffocation which is brought about by hydrocyanic acid. This acid deprives the body’s tissues of the ability to absorb oxygen from the blood. Other unpleasant symptoms include headache, shivering, faintness, vomiting, paralysis and convulsions. A large dose of the fruit will almost certainly prove lethal, eventually suffocating the victim.

LaurelIt is estimated that a third of all flora is fatally poisonous if taken in the wrong dose. Since discovering this I have reflected on my education so far and wondered if have been approaching herbalism and foraging from the wrong angle – perhaps a detailed knowledge of poisonous plants is what I should have started with? Clearly it is crucial to know what is toxic and what is safe as mistakes can be disastrous.

By Claire Fleetneedle




  • As the sign on Alnwick’s poison garden gates states, ‘These plants may kill’. Consequently this article is for interest only. None of the plants should be consumed under any circumstances. Ingesting any of them could lead to permanent nerve, heart, internal organ damage or death.