File:Monk's-hood (an Aconitum species) - geograph.org.uk - 1014884.jpg

English: Monk's-hood (an Aconitum species). This patch of Monk's-hood was growing in vegetation alongside the canal path.

[The native species of Monk's-hood is Aconitum napellus agg., the "agg." in the scientific name indicating that it is a "recording aggregate", the name given to a grouping of several subspecies that are difficult to distinguish in the field. Hybrid Monk's-hood, Aconitum × cammarum, is also common, having spread from gardens and become naturalized in the wild; this is probably the species that is shown in the photo.]

According to "Flora Britannica" (Richard Mabey), Monk's-hood is "probably the most virulently poisonous of all British plants, yet its hooded, bonnet-like blue flowers have made it a favourite border plant"; the same work goes on to relate that "even skin contact can be dangerous. In 1993, there was an epidemic of poisoning at a florist's in Wiltshire: 'a flower seller was treated for heart palpitations in intensive care after handling bunches of a poisonous flower .... staff at a flower shop in Salisbury suffered shooting pains after poison from a monkshood entered their bloodstreams.'"

The plant contains several potent cardiac poisons, including aconitine. Other particularly poisonous but commonly encountered wild flowers include 963809 and 942492.