Plant 82

Aconitum napellus L. (Ranunculaceae)



Monkshood, friar's hood, auld wife's huid and wolfsbane, common names for Aconitum napellus, hint at the plant's flower shape and toxicity. Wolfsbane was coined by the English 'father of botany' William Turner in 1548 from the classical names for 'wolf-killing'. Over millennia, across the northern hemisphere, the genus Aconitum had acquired a formidable, and deserved, reputation as a poison; ingesting a few grams of the fresh tuber can lead to a prolonged, agonising death. The genus was used by assassins and physicians and even the elderly of ancient Chios when they were passed their prime. In popular culture, among swirling mists and unconvincing flowering stalks, the fashionable mythology of lycanthropy was created in George Waggner's classic film The Wolf Man (1941), where even a man pure in heart may become a wolf when the wolfsbane blooms!

In the mid-sixteenth century, the Italian physician Pietro Andrea Mattioli reported condemned prisoners were given monkshood to test the medieval belief that bezoars (concretions in animal guts) were poison theriacs. The immediate effects of the toxic cocktail of diterpene alkaloids (e.g., aconitine) include reduced heart rate, burning, tickling, numbness and sensations of having fur or feathers. Aconitum napellus was introduced to Britain, from continental Europe, before the 1590s, probably as a drug plant. Today, monkshood is redundant as a medicine but is widely naturalised in Britain and remains a spectacular early-summer garden perennial.

Carolus Linnaeus based his generic name on an ancient Greek name for a yellow-flowered species. Explanations for the ancient name's origin have ranged from a place in Pontus where the plant was abundant, through the plant's rocky habitat to its use as an arrow poison. Napellus (little turnip) refers to the blackish, tuberous root.

The bilaterally symmetrical Aconitum napellus flower has a blue-purple perianth of five tepals. The upper tepal forms a hood which hides two elaborate, stalked nectaries, an abundance of stamens and three carpels. The flower is adapted for bumblebee pollination, the bee exploiting the lower tepals as a landing platform, forcing its way inside the flower, using its long tongue to get a nectar reward and becoming covered in pollen. Initially, the stamens bend forwards but as the flowers ages they become erect and once the pollen has been released they bend backwards. After pollen release, the exposed stigmas mature and pollination can happen. Some insects puncture the back of the tepals, steal the nectar and by-pass cross-pollination.

Further reading

Jabbour F, Renner SS 2012. Spurs in a spur: perianth evolution in the Delphinieae (Ranunculaceae). International Journal of Plant Sciences 173: 1036-1054.

Mayer C et al. 2014. Nectar robbing improves male reproductive success of the endangered Aconitum napellus ssp. lusitanicum. Evolutionary Ecology 28: 669-685.

Stephen Harris