Foxglove

Foxglove

We all know the foxglove. Their tall stems, with an array of bell shaped flowers in those vivid colors of pink and purple, or even white, draw your attention to them. In the spring we are surrounded by foxgloves. They can be six feet (two meters) tall, and  are a pleasure to look at. I was told not to touch them because they are poisonous. But I could take photos and saw how interesting those bells were. When you look into the bells you see all the spots and the little hair around the rim of the bell.

Leonhard Fuchs

So why are they called foxglove? Leonhard Fuchs (the German word for fox) named them in 1542 and put them in the genus of Digitalis (finger-like). In Old English it then became foxes glofe or fox’s glove. Over time people thought that foxes had their dens on hillsides covered with these flowers. And some people called the flowers “witch’s glove,'' referring to their toxicity.

Our foxgloves - the common foxglove,  with the Latin name Digitalis purpurea, is commonly found in open woods, but also where the vegetation has been burnt. If the genus name Digitalis seems to jump out at you, it is probably because that is the name of a popular family of heart medications for people. If it is so toxic, why would we be giving its derivatives to people with heart problems? That’s a very fair question.

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William Withering

The use of plants for medicinal reasons is very old. The Chinese have used plants as medicine since 4000 - 5000 B.C. The earliest  known medical document is 4000 years old. It is a Sumerian clay tablet that recorded plant remedies for various illnesses. Indeed, botanical compounds are still the basis for most of our pharmaceuticals today, six millennia later. As we battle to overcome the new ‘superbugs’ that are resistant to our current antibiotics, we are scouring the world’s rain forests for new compounds that may save us from our over use of modern antibiotics. (Another reason that there is so much panic in the current news stories of rampant fires burning down a soccer field’s amount of old growth rain forest every minute in Brazil, and the current offer of the G7 to supply them with twenty million dollars in fire fighting aid (8/28/19). The remedy may still be lurking in the rain forests.)

Leonard Fuchs discovered the plant in the 16th century, but it was forgotten due to the severe toxicity and the deaths of some patients. But then in 1741 it was rediscovered by William Withering. He went to medical school in Edinburgh, where he became interested in botany, chemistry and mineralogy. After medical school he became a country doctor in Stafford, a small and very poor town in England. One of his patients was an old woman dying of dropsy (now known as edema or water retention). He expected her to die quickly, but she recovered. She had taken a mixture of herbs. Dr. Withering realized that the main herb was the flowering foxglove.

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He gave the mixture of herbs to another 163 patients and made detailed notes on the effect of foxglove. The notes contain toxicity, dosing and side effects. Some of the side effects were vomiting, confusion, slow pulse and cold sweats. All of the patients had a slow pulse, which led later investigators to explore using it for heart problems.

Since the discovery, digitalis has been debated whether the toxicity outweighs the benefits. Interestingly, doctors still use digoxin when treating congestive heart failure, in spite of the modern know how of the pharma industry. The compounds are extracted from the leaves of the plant. 

Foxgloves were always used by folklorists. Once the usefulness of digitalis was understood, it was also used for the treatment of epilepsy and other seizure disorders. 

The entire plant is toxic, including the roots and seeds. Mortality cases are rare, but they exist. If one uses the foxglove  for tea or eats them, nausea, vomiting, hallucinations will occur. It is said that Vincent van Gogh’s “Yellow Period” was the result of digitalis therapy, which he went through to control his seizures.

However, the larvae of the foxglove pug, a moth, consume the flowers of the common foxglove for food! And they go on living. This is not an uncommon dynamic in nature. Much like the beautiful and brightly colored Monarch butterfly’s diet of common milkweed nectar - which is also toxic to most animals, confers on them protection from predators. The Monarch’s bright colors warn predators that their bodies are poisonous to eat, if not sickening. Many insects are protected in this way. Generally speaking, the brighter and more vibrant the markings, the less desirable they are as a food.

So this common dynamic - of evolving to consume toxic substances to ward off predators, begs a question! A brief survey of poison control sites, informs us that all parts of the plant are toxic to all animals. Yet hummingbirds thrive on foxglove nectar. Hummingbirds are hunted and eaten by a wide variety of animals, from snakes and lizards, to praying mantises and orb spiders, frogs and even fish. Of course birds will hunt them as well. Is it just the nectar that is not toxic, or has the hummingbird evolved to be immune to the toxicity for just the food source, without it conveying any protection from predators?  Just curious.

Let me end with a poem about foxgloves, written in Dr. Withering’s time (unknown author):

“The Foxgloves leaves with caution given
Another proof of favouring heaven
Will happily display
The rapid pulse it can abate
The hectic flush can moderate
And, blest by Him whose will is fate,
May give a lengthen’d day.”