Jeremy Bartlett's LET IT GROW blog

We’ve had a magnificent display of Foxgloves this year, after all the rain.

The Foxglove, Digitalis purpurea, is one of my favourite flowers and I can’t help smiling when I see one.

One Foxglove is lovely but a mass of Foxgloves is even better.

Foxgloves, Digitalis purpurea, on our allotment. 3rd June 2024.

Digitalis purpurea is a biennial or short-lived perennial herb. It forms a sturdy rosette of leaves in its first year and then a tall flower spike in its second. The plant expends a lot of energy in flowering and often dies straightaway, but sometimes survives to flower less spectacularly the next summer. There is normally only one flower spike per plant but if the flowering stalk is damaged early in its growth, multiple flower spikes can form.

After flowering a Foxglove sets large amounts of seed and the seeds will germinate if there is bare soil and plenty of light, but when the conditions are unsuitable seeds can survive in the soil’s seed bank and produce plants in subsequent years.

Disturbance of the soil and opening up of a tree canopy can trigger a mass germination of Foxglove seeds and Foxgloves can be found in great abundance in disturbed or burnt areas, such as beside tracks and roads or in recently felled forestry plantations.

Digitalis purpurea occurs in nearly every 10km square in the British Isles. Foxgloves like acidic soils, but are a popular garden plant and many of the records in places with alkaline soils are probably garden escapes. The BSBI Plant Atlas lists Foxgloves’ habitats in the British Isles as on hedge banks, in open woods and woodland clearings, on heathland and moorland margins, riverbanks, montane rocky slopes, sea-cliffs, walls and waste land. They can grow quite happily on hillsides with Bracken (Pteridium aquilinum), rising above the fern’s green canopy (note 1).

The name “Foxglove” can be traced back to the Old English “foxes glofa“. The shape of the flower suggests the finger of a glove and, in “Flora Britannica” Richard Mabey suggests the “fox” part of the name comes from the plant’s habit of growing in “foxy places” (note 2). The name “Digitalis” comes from the Latin digitus (finger).

Foxgloves, Digitalis purpurea, in Oaken Wood, Chiddingfold. 6th June 2018.

When I first studied plants Digitalis purpurea was a member of the family Scrophulariaceae but it was moved to the Veronicaceae in 2001 and nowadays it is considered to be in the Plantaginaceae (note 3).

Worldwide there are about 20 species of Digitalis, all native to Europe, western Asia and north-western Africa.

Digitalis purpurea is native to Belgium, Corsica, the Czech Republic and Slovakia, France, Germany, Great Britain, Ireland, Morocco, Portugal, Sardinia, Spain and Sweden. It has been introduced to many other parts of the world, including large parts of North and South America, several eastern European countries, New Zealand, Tasmania and Zimbabwe. Foxgloves feature in the Invasive Plant Atlas of the United States.

Foxgloves started to flower in mid May this year here in Norfolk but the main flowering period starts in early June. It can continue into September, depending on location. The flowers are a pinky-purple and have spots inside the flower tube. They attract bumblebess, particularly the Garden Bumblebee, Bombus hortorum, Buff-tailed Bumblebee, Bombus terrestris, and the Common Carder Bee, Bombus pascuorum.

Foxglove flowers – close up.

White-flowered Foxgloves occur naturally and are often grown in gardens.

The Wild Flower Finder website has pictures of other variations of Foxglove flowers.

Also available in white. Foxglove, Digitalis purpurea.

A few weeks ago as I walked past a garden on the other side of our road I noticed a Foxglove with an unusual flower. Most of the flower spike was normal but the top flower was open to the skies and didn’t form the usual tube of fused petals.

This development is known as a terminal peloric flower. Peloric flowers are radially symmetrical flowers that occur in species which normally have flowers with bilateral symmetry.  “Terminal” refers to the flower’s position at the top of the flower spike. “Peloria” is from the Greek word for monster.

The Royal Botanic Gardens Kew website has an interesting article by Paula Rudall, “Weird and Wonderful Foxgloves”, which describes the phenomenon. Breeding experiments have shown that the terminal flower mutation in Digitalis is passed on to the plant’s offspring as a simple Mendelian recessive trait.

Foxglove with a terminal peloric flower.

Close up of the terminal peloric Foxglove flower.

Peloric flowers also can be found in other species which normally have bilateral flowers, such as mints, orchids and Snapdragon (Antirrhinum).

When I a PhD student at the John Innes Centre in the late 1980s, scientists were studying the cause of peloric flowers in Antirrhinum and a resulting scientific paper was published in the journal ‘Nature’ in 1996 as “Origin of Floral Asymmetry in Antirrhinum“.

Foxgloves, St. Agnes, Isles of Scilly. 20th June 2010.

Foxgloves are poisonous but have a bitter taste so are not tempting to eat. If eaten, vomiting occurs before large amounts of toxins can be absorbed. Symptoms of poisoning include nausea, vomiting (sometimes for more than 24 hours), abdominal pain, diarrhoea, headache and a slow and irregular pulse. Cooking doesn’t destroy the toxins (note 4).

Historically Foxgloves were used as a purgative and the botanist John Parkinson said that they “purge the body both upwards and downwards” (cause diarrhoea and vomiting).

In the late 18th Century the English botanist and physician William Withering used extracts of Foxglove leaves to treat dropsy, an accumulation of fluid in soft tissues caused by a weakness of the heart (note 5). Dosage was critical and too much Foxglove leaf could stop the heart altogether. Withering insisted on using small, accurately measured amounts of dried Foxglove leaf and in his careful research was one of the founders of modern clinical pharmacology.

The active ingredients in Foxgloves are the cardiac glycosides digitoxin and digoxin and they are still widely used in medicine as heart stimulants. They are still extracted from Foxglove plants, but usually from species other than Digitalis purpurea (such as the southern European Digitalis lanata) (note 6).

Notes

Note 1 – The Wild Flower Finder website has a good picture of this.

Note 2 – Where you might find a Fox. Pages 332 – 333 of Richard Mabey’s “Flora Britannica” (Sinclair-Stevenson, 1996).

Note 3 – In Stace’s Flora Digitalis is part of the Veronicaceae. Page 618, “New Flora of the British Isles“ by Clive Stace, Fourth Edition, 2019.

Note 4 – From pages 74 – 75 of “Poisonous Plants and Fungi – An Illustrated Guide” by Marion Cooper and Anthony Johnson, HMSO, 1994.

Note 5 – Nowadays dropsy would be diagnosed as congestive heart failure – the inability of the heart to keep up with the demands on it.

William Withering may have learnt of the cure for dropsy from “an old woman in Shropshire” but the widely quoted story that “Mother Hutton”, a herbalist from Shropshire, sold William Withering the cure for dropsy is a myth invented by a pharmaceutical company for marketing purposes.

Note 6 – During the Second World War native Foxglove leaves were gathered in large quantities for medicinal use, as European plants were unavailable. The harvest was co-ordinated by the County Herb Committees. Careful drying was necessary to preserve the cardiac glycosides.