Alnwick Poison Garden entrance

Photo: Chris Morgan/geograph

Looking for a window into the strange world of poisonous and psychoactive plants? Search no further than the Poison Garden in Alnwick, Northumberland, England.

The deadly attraction, situated within the 42-acre Alnwick Gardens, features over 100 plant species of varying degrees of toxicity. While some of these species are uncommon, you might be surprised to learn there are plenty of killer plants in your backyard right now!

Due to the potentially dangerous nature of the plants inside the exhibit, visitors to Alnwick must enter the Poison Garden through an exceptionally intimidating and locked gate:

Alnwick Poison Garden sign

Photo: Jo Jakeman/Flickr

Jane Percy, the Duchess of Northumberland, was instrumental in the redevelopment of the Alnwick Garden, which boasts a long history dating back to the 18th century, but fell into disrepair in the 1950s. After more than a half-century hiatus, the Alnwick Garden reopened to the public in 2004. Much to the delight of morbid botanists everywhere, the launch of the Poison Garden followed soon after.

"I wondered why so many gardens around the world focused on the healing power of plants rather than their ability to kill," the Duchess explains on the Poison Garden website. "I felt that most children I knew would be more interested in hearing how a plant killed, how long it would take you to die if you ate it and how gruesome and painful the death might be."

Alnwick Poison Garden ivy tunnel

Photo: Graeme/Flickr

It may be a small garden, but the stories behind these otherwise unassuming plants pack quite a punch. Knowledgeable guides lead visitors around the premises, sharing both the mythical folklore and hard science associated with each species.

Alnwick Poison Garden cannabis cage

Photo: Duncan Andison/Shutterstock

Because several of the plants on exhibit are especially lethal or outright illegal, the garden require special licensing to grow them. Some plants, like the cannabis seen above, must be confined to cages to limit their contact with visitors.

Alnwick Poison Garden pathway

Photo: Miss Steel/geograph

Although there are many lethal plants thriving behind the guarded gates of the Poison Garden, here's just a few of the most intriguing species you're likely to find there:

Alnwick Poison Garden: Ricinus communis

Photo: Sarah Murray/Flickr

Castor oil plant (Ricinus communis)

Generally considered to be the most poisonous plant in world, the castor oil plant's raw seeds contain ricin, a highly toxic substance that inhibits the synthesis of protein. Ingesting just four to eight of the seeds can kill a human, but not before he or she suffers through a host of unpleasant symptoms, including but not limited to nausea, seizures, diarrhea, purging and abdominal pain.

Alnwick Poison Garden: Opium poppy buds

Photo: Dave/Flickr

Opium poppy (Papaver somniferum)

Opium, which has been cultivated by humans for thousands of years, is made by drying and processing the milky latex liquid found within a poppy seed pod. As the root source of many strong narcotics such as morphine, heroin, codeine and more, it's no wonder why the opium poppy is granted a spot in a garden specifically devoted to lethal plants.

Alnwick Poison Garden: Pasque flower

Photo: Randi Hausken/Flickr

Pasque Flower (Pulsatilla vulgaris)

These hairy plants can be fatal if eaten in large amount, but it rarely comes to that. Due to its strong, bitter taste that produces an immediate burning sensation in the mouth, it doesn't take long for the person ingesting it to spit it out.

Alnwick Poison Garden: Black henbane

Photo: jacinta lluch valero/Flickr

Black henbane (Hyoscyamus niger)

These striking flowers are so potently hallucinogenic that even their smell can produce giddiness. When taken recreationally, they cause intense visual, tactile and auditory hallucinations, as well as a host of uncomfortable side effects including dry mouth, fever, vomiting, dilated pupils, rapid heart rate and delirium. Severe overdoses are characterized by convulsions, hypertension, falling into a coma or even death.

Alnwick Poison Garden: Columbines

Photo: _seb/Flickr

Dark Columbine (Aquilegia atrata)

There are actually no recorded cases of these drooping purple flowers harming anyone, but folklore suggests the plant was used as an abortifacient for women hoping to produce a miscarriage.

Alnwick Poison Garden: Foxgloves

Photo: liz west/Flickr

Common Foxglove (Digitalis purpurea)

These flowers may look lovely and benign, but they can actually cause a major heart attack if eaten in large amounts. Luckily, this is rare because the plant also happens to be an emetic, which is a substance that naturally triggers vomiting. If ingested, the poison is usually purged from the digestive system before it can do much damage to the cardiac muscles.

Catie Leary is a photo editor at Mother Nature Network. Follow her on Twitter and Google+.

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Catie Leary ( @catieleary ) writes about science, travel, animals and the arts.

'Poison Garden' showcases the darker side of botany
Witness the world's most poisonous and psychoactive plants at the Alnwick Poison Garden.