Foxglove

The foxglove, Digitalis purpurea, is a tall biennial of European woods and banks bearing a one-sided spike of drooping purple thimble-shaped flowers. Its beauty must be met at once with a warning: the foxglove is deadly poisonous in every part, containing potent cardiac glycosides that act powerfully on the heart, and it has killed people and livestock, a fact stated here plainly and not as any invitation to use it. Its name is usually explained as the folk's glove or fairy folk's glove, the flowers being the gloves or bells of the little people, and its many country names, fairy thimbles, witch's gloves, dead men's bells, tie it closely to the fairy world and to death.

The specific compounds responsible, cardiac glycosides including digitoxin and digoxin, work by interfering with the sodium-potassium pump in heart muscle cells, altering the force and rhythm of the heartbeat, the same mechanism that makes purified digoxin a genuine prescription medicine for certain kinds of heart failure and irregular heart rhythm today, used under close medical supervision because the safe dose and the dangerous dose are dangerously close together, a narrow margin that makes the raw plant especially hazardous to anyone attempting to use it without exact pharmaceutical measurement.

In folk belief the foxglove belonged to the fairies: it grew where they dwelt, its spots were the marks of their fingers or of elf-warning, and it must not be brought carelessly into the house. It was a plant of the threshold between the human and the fairy world, protective in some tellings and perilous in others. There is a genuine and important footnote of medical history attached to it: in 1785 the English physician William Withering published his study of the foxglove and its use in dropsy, and the heart drug digitalis derives from the plant to this day, a historical fact given here as history only, which in no way makes any part of the raw plant safe to handle or consume. Fairy glove and deadly beauty, the foxglove is a flower to admire and never to touch to the lips.

Digoxin, the purified compound descended from Withering's original foxglove research, remains on the World Health Organization's Model List of Essential Medicines to this day, more than two centuries after an old Shropshire herbalist's home remedy was first taken seriously by a trained physician, one of the longer continuous threads running from a single English physic garden into the modern global pharmacy, and it stands as one of the clearest examples in this entire atlas of a plant's two faces meeting exactly, the same chemistry that can kill in the wrong hands saving lives every day in the right ones.