Garden History Medicinal Plants Poisonous Plants

The Plant That May Have Driven Vikings Berserk

Vikings in a state of uncontrollable rage terrified settlements throughout Western Europe from the late 8th to the early 11th century, but what made them go berserk? Ill.:

Everyone knows the term “berserk”. It derives from the Old Norse word berserkergang, a trance-like state of blind rage where men (berserkers) fought with superhuman strength, oblivious to pain, and said to have been characteristic of Vikings in battle. 

The fly agaric is practically the fairy tale mushroom… and can be deadly if consumed. Photo: Onderwijsgek, Wikimedia Commons

For many years, the main theory behind the origin of this state was the consumption of a hallucogenic toadstool (mushroom) called fly agaric (Amanita muscaria) just before a battle. But ethnobotanist Karsten Fatur of the University of Ljubljana in Slovenia has a new theory: that Vikings were instead consuming leaves or seeds of henbane (Hysocyamus niger), a common weed. 

Fly agaric, a surprisingly attractive though highly toxic mushroom, can certainly cause some of the symptoms of berserkergang: increased strength, redness of the face, delirium, dilated pupils, jerking and twitching, etc., but it’s a poor match for anger. Instead, it tends to have a serious calming effect. It even has a long history of use as an anesthetic. That doesn’t sound like something that would make you go berserk.

Also, argues Fatur, fly agaric was not a common mushroom in Scandinavia, being mostly found in the broad-leaf forests of Central Europe rather than the coniferous ones of the North. 

Henbane (Hysocyamus niger). Photo:

He suggests henbane (Hysocyamus niger), also known as black henbane or stinking nightshade), would have been a more likely culprit. When consumed, this plant provokes most of the same symptoms (increased strength, redness of the face, delirium, dilated pupils, jerking and twitching), but also agitation and full-blown rage and combativeness. Henbane is poisonous too, but, as with many poisonous plants, also has a long history of use as a medication when properly diluted. The poison, as they say, is in the dose. It was actually used in making early European beers, although has long since been replaced by hops (Humulus lupulus). 

From the point of view of Vikings seeking to stoke themselves into a terrifying battle frenzy, henbane also has the advantage of having been an abundant wildflower in Scandinavia and its seeds were known to have been collected by Scandinavian peoples. Indeed, a pouch of henbane seeds was found in a woman’s grave in Denmark dated to Viking times: about 980. 

What is Henbane?

You may know henbane as a garden weed. Originally from Eurasia, it was introduced over much of the world as a medicinal plant and is now found growing sporadically on all continents except Antarctica. 

Henbane can be attractive in appearance, but the smell is less appetizing! Photo: Mikenorton, Wikimedia Commons

The name bane refers to a poisonous plant (think of dogbane, bugbane, etc.), so henbane seems to suggest it is poisonous to chickens, although another theory is that “hen” could also mean “death”. It’s toxic to most mammals and birds, even fish, yet pigs are immune to henbane toxicity and seem to relish eating it. So do Colorado potato beetles (it’s a member of the Solanaceae family, along with potatoes and tomatoes). 

It’s actually quite an attractive plant… from a distance, with numerous bell-shaped pale yellow or cream flowers with purple veins and a dark purple center that are borne on an upright plant with large, irregularly lobed leaves covered in sticky hairs. Up close you can’t help but notice, though, that the plant gives off an obnoxious odor probably designed either to keep predators away or to attract carrion flies, which are its main pollinators. Sniffing henbane too deeply is said to be able to cause dizziness. 

Henbane also appears to be a passive carnivore, much like its cousin, the tomato plant: insects become stuck on its sticky leaves, die, then decay, nourishing the plant. 

The stinky flowers attract carrion flies. Photo: Lliam Rooney, flickr

You might wonder why anyone would want to grow a plant known to be stinky, seriously poisonous, attractive to flies and weedy, but there is a lot of interest in medicinal plants these days and henbane has thousands of years of use in that field, from the ancient Greeks to modern times. It’s very rich in toxic alkaloids (some 34 have been discovered!) including hyoscine (scopolamine), hyoscyamine and atropine. It’s been used to treat coughs, toothache, asthma, nervous diseases, travel sickness, rheumatism and stomach pain, but the dose has to be rigorously controlled, as it is highly poisonous, with even modest doses sometimes leading to coma and even death*.

*If you’re interested in the medicinal use of plants, I suggest you consult a science-based book or website on the subject. 

Some believe that the concept of witches flying on broomsticks is linked to the hallucinatory effect of taking henbane. Ill.:

Henbane is likewise strongly associated with witchcraft due to its reputation for causing hallucinations and delirium.

Growing Henbane

Henbane seeds are quite easy to find on the Internet. Richters Herbs offers it, among others. As a potential weed, it is illegal to sell in the US states California, Nevada and North Dakota.

It’s usually considered an overwintering annual or biennial, that is, a plant you sow one year and that survives the winter (it is hardy in USDA zones 3 to 9) to bloom the following summer (July and August), after which it produces seed, then dies. You can grow also it as an annual if you sow it outdoors early in the spring while the soil is still quite cold. It can be sown indoors as well, but will then germinate better if given a few weeks of cold stratification in the refrigerator. When grown as an annual, henbane usually attains no more than half the 3 to 4 feet (90-120 cm) height it reaches when grown as a biennial.

Henbane is adapted to full sun and fairly dry conditions, doing fine in poor soils, but grows on rich soils as well. Sow the seed on the surface of the soil without covering it: the seeds need light to germinate. Soaking them in cold water for 24 hours before sowing can help stimulate better germination.

Henbane rarely becomes usually only becomes invasive in poor, dry soil. Photo:

Henbane will self-sow in bare spots (it doesn’t tolerate competition for light), but it’s rarely a very vigorous weed except in arid climates and poor soil. However, do be forewarned that the seeds can remain dormant for years, even decades, then pop up when you thought the plant was long gone. 


Is henbane really behind the berserk behavior of rampaging Vikings? It’s still just a theory, but an interesting one!

Read the article “Speculative ethnobotanical perspectives on the Norse berserkers” by Kirsten Fatur here:

Garden writer and blogger, author of 65 gardening books, lecturer and communicator, the Laidback Gardener, Larry Hodgson, passed away in October 2022. Known for his great generosity, his thoroughness and his sense of humor, he reached several generations of amateur and professional gardeners over his 40-year career. Thanks to his son, Mathieu Hodgson, and a team of contributors, will continue its mission of demystifying gardening and making it more accessible to all.

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