Question: Why are fox gloves poisonous?

Sara Imari Walker answered on 17 Jun 2011:

Hello nsweeney!! Fox gloves are an interesting plant aren’t they? I just looked this up – fox gloves are a plant family called digitalis, which has over 20 species. They contain several deadly physiological and chemically related cardiac and steroidal glycosides. Early symptoms of ingestion of fox glove toxins include nausea, vomiting, diarrhea, abdominal pain, wild hallucinations, delirium, and severe headache. Depending on the amount ingested, the victim can later suffer irregular and slow pulse, tremors, various cerebral disturbances (in particular unusual color visions), convulsions, and heart failure. Fox gloves have some very deadly toxins!

I like that you asked “why” are fox gloves poisonous. The above address the “what” of what makes fox gloves toxic. The why might be even more interesting. Most likely fox gloves are poisonous as an evolved defense mechanism. An ancient ancestor of modern fox glove was likely not toxic and at some point a mutation arose which led a few plants to produce this toxin. More of those plants were able to survive and reproduce (since no one wants to eat a toxic plant!) than their nontoxic counterparts and so the modern fox glove that eventually emerged kept the most successful traits for survival – including toxicity! Ack, I wouldn’t want to make tea from a foxglove 😉