Monday, May 09, 2011


I found myself daydreaming about the foxglove, a lovely flower that is ubiquitous in the English landscape and appears from time to time in my garden. It's an easy plant to grow from seed, and can propagate itself from seed in the garden quite nicely. Looking back, I've grown three types, Digitalis purpurea (common foxglove), Digitalis grandiflora (perennial foxglove), and Digitalis mertonensis (strawberry foxglove). D. grandiflora is perennial and hardy, D. mertonensis is a short-lived perennial (a tetrapolid cross between D. grandiflora and D. purpurea) and D. purpurea is a biennial. Biennials grow foliage in the first year, and flower and set seed in the second year. The biennials die after setting seed. All should be planted in the ground in northern climates, as they will not survive the winter in a pot in zone 3 or colder.
Digitalis grandiflora in the rock garden:

Digitalis also one of those plants we are warned about as being poisonous, due to its content of chemicals that act on the heart. For the same reason, it is one of the most medically famous plants. The plant contains chemicals used in the heart drug digoxin (Lanoxin), a medication used for certain heart diseases (usually atrial fibrillation or heart failure), acting to slow and strengthen the heart beat. Overdose of the drug can result in cardiac arrest. As such, it is a drug (and plant) you must be careful with. I'd imagine the next 20 years of medical research will probably replace this drug with something a little less risky and easier to manage.

An antidote, called Digifab or Digibind, can be given intravenously to mop up toxic levels of digoxin and allow it to exit the body harmlessly via the kidneys. The product monograph is fascinating -- Digifab is made when sheep are injected with a digoxin-derivative attached to a chemical from the keyhole limpet (tiny crustacean that clings to rocks and boat hulls). The sheep serum extract is digested with a bit of pineapple enzyme and the important bits are separated out with a little chromatography, and voila!
Digitalis mertonensis in the raised bed:

Foxglove use was documented in medieval times, as an agent used by witches, when the plant was sometimes called witchs' bells. In the 18th century, a physician (William Withering) noticed that an old woman concocting herbs was having some success in treating edema (likely due to heart failure), and he is credited for discovering that among her collected weeds, digitalis was the effective tonic.
Some self-seeded Digitalis purpurea:

The medicine digoxin is extracted from Digitalis lanata, the wooly foxglove. Apparently, it is cheaper to extract the digoxin from the plant than it is to synthesize the chemical. Presumably, there are medicinal Digitalis farms in existence somewhere.

I have some Digitalis purpurea plants that will flower this year in my perennial beds, but in the interest of trying new and different plants, I would like to try some others. There is a good selection on this American mail order website, which I have ordered from before. I had no idea there were so many kinds! Digitalis are so easy to grow from seed, that I feel wasteful spending good money for them as plants at the nursery.

On the topic of other beautiful flowering plants - here are some pics from another blog, of National Primrose Society Show prize-winning flowers. Amazing.


Anonymous said...

Very interesting. I love this flower. Unless the kids dig up the seeds from the ground we don't have much of a poison hazard as of yet!!

Check out the horrendous picture on my blog of "the barrel"


turtlegarden said...

Good Evening,
Your garden looks lovely. I think that your photos have helped me identify a plant in a garden on the side of my building that I just inherited this year. I am very familiar with foxgloves as they grow wild on Bowen Island where I spent a lot of time.
The plant looks like a foxglove but is a pale creamy yellow and lots of spear shaped leaves. The flower stalks are close to the leaves, not high on stalks.
This could be due to location and soil.
I live in Vancouver right in the heart of the city. I have a plot in a community garden as well, but there I grow mainly vegetables.
Anyway, thank-you for the foxgloves. I love them too.