''Digitalis purpurea'', the foxglove or common foxglove, is a toxic
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of
flowering plant
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...
in the
plantain family Plantaginaceae
Plantaginaceae, the plantain family or veronica family, is a large, diverse family (biology), family of flowering plants in the order Lamiales that includes common flowers such as Antirrhinum, snapdragon and Digitalis, foxglove. It is unrelated ...
,
native to and widespread throughout most of
temperate
In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...
Europe. It has also
naturalized in parts of North America, as well as some other temperate regions. The plant is a popular garden subject, with many
cultivars available. It is the original source of the heart medicine
digoxin (also called digitalis or digitalin). This
biennial plant grows as a rosette of leaves in the first year after sowing, before flowering and then dying in the second year (i.e., it is
monocarpic). It generally produces enough seeds so that new plants will continue to grow in a garden setting.
Description
''Digitalis purpurea'' is an
herbaceous biennial or short-lived perennial plant. The leaves are spirally arranged, simple, long and broad, and are covered with gray-white pubescent and glandular hairs, imparting a woolly texture. The foliage forms a tight rosette at ground level in the first year.
The flowering stem develops in the second year, typically tall, sometimes longer. The flowers are arranged in a showy, terminal, elongated cluster, and each flower is tubular and pendent. The flowers are typically purple, but some plants, especially those under cultivation, may be pink, rose, yellow, or white. The inside surface of the flower tube is heavily spotted. The flowering period is early summer, sometimes with additional flower stems developing later in the season. The plant is frequented by bees, which climb right inside the flower tube to gain the
nectar within.
The fruit is a
capsule which splits open at maturity to release the numerous tiny 0.1-0.2 mm
seed
In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...
s.
Distribution
Native range
Digitalis purpurea has a native range that spans across several countries in
Western Europe
Western Europe is the western region of Europe. The region's extent varies depending on context.
The concept of "the West" appeared in Europe in juxtaposition to "the East" and originally applied to the Western half of the ancient Mediterranean ...
and
North Africa
North Africa (sometimes Northern Africa) is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region. However, it is sometimes defined as stretching from the Atlantic shores of t ...
. In Western Europe, it is native to Belgium, Czech Republic, France, Germany, Ireland, Norway, Portugal, Spain, Sweden and the United Kingdom. In North Africa the species can be found in Morocco. Additionally, it occurs naturally on the islands of Corsica and Sardinia.
Introduced range
''Digitalis purpurea'' has been introduced throughout the world into countries and continents outside of its natural range. Due to introductions, the species has expanded its range further into Europe and Africa, as well as colonizing continents outside of the natural range, including
Asia
Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...
,
North America
North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
,
South America, and
Oceania.
''Digitalis purpurea'' has been introduced extensively throughout Europe, including Austria, the Baltic States, Belarus, Denmark, Hungary, the Netherlands, Poland, Réunion, and Ukraine. It has also found its way to the Azores, the Canary Islands, Central European Russia, Madeira, and the Sakhalin and Kuril Islands.
In
North America
North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
, it has been introduced into more than twenty states of the
United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
: Arkansas, California, Connecticut, Idaho, Maine, Maryland, Massachusetts, Michigan, Montana, New Hampshire, New Jersey, New York, North Carolina, Ohio, Oregon, Pennsylvania, Vermont, Washington, West Virginia, Wisconsin, and Wyoming. In
Canada
Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
, it has colonized multiple provinces, including British Columbia, New Brunswick, Newfoundland, Nova Scotia, Ontario, and Québec.
In South America, ''Digitalis purpurea'' has been introduced into Argentina, specifically in the regions of Northeast, Northwest, and South. It also can be found in Bolivia, Brazil (specifically the South and Southeast regions), Chile (Central region), Colombia, Costa Rica, Cuba, Ecuador, El Salvador, Guatemala, Jamaica, Mexico (Central, Gulf, Northeast, Southeast, and Southwest regions), Peru, Uruguay, and Venezuela.
''Digitalis purpurea'' has made its way to various regions of
Asia
Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...
, including China (specifically the South-Central and Southeast regions), Korea, and Vietnam. In
Africa
Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...
, it can be found in Malawi and Zimbabwe. Furthermore, it has been introduced to the island nations of
New Zealand
New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...
, both the North and South Islands.
It is also an established weed across multiple locations in Tasmania, Australia.
Subspecies and hybrids
*''Digitalis purpurea'' subsp. ''purpurea'' – most of Europe and
Macaronesia and widely introduced to other parts of the world.
*''Digitalis purpurea'' subsp. ''amandiana ''
( Samp.) P.A.Hinz – northern
Portugal
Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...
(specifically around the
Douro Basin).
*''Digitalis purpurea'' subsp. ''mauretanica ''
(Humbert & Maire) A.M.Romo –
Morocco
Morocco, officially the Kingdom of Morocco, is a country in the Maghreb region of North Africa. It has coastlines on the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to Algeria–Morocc ...
.
*''Digitalis purpurea'' subsp. ''toletana''
(Font Quer) P.A.Hinz – central
Spain
Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...
.
*
''Digitalis'' × ''fulva'' Lindl. 1821 (hybrid formula:
''D. grandiflora'' × ''purpurea'').

''Digitalis purpurea'' subsp. ''mariana'' is a
synonym for
''D. mariana'' subsp. ''mariana'',
and ''D. purpurea'' subsp. ''heywoodii'' is a synonym for
''D. mariana'' subsp. ''heywoodii''.
[
''D. dubia'', a name used for populations of foxglove growing among calciferous rocks on shady cliff faces on the island of Majorca, is now considered a synonym of ''D. minor'',] but until recently it had been either considered to be a valid species (i.e. in the '' Flora Europaea'' (1976), and the ''Euro+Med Plantbase'' (2011)), as well as classified as ''D. purpurea'' subsp. ''dubia'' in 1922, or ''Digitalis purpurea'' f. ''dubia'' by Spanish taxonomists in 1983.
Ecology
''Digitalis purpurea'' grows in acidic soils, in partial sunlight to deep shade, in a range of habitats, including open woods, woodland clearings, moorland and heath margins, sea-cliffs, rocky mountain slopes and hedge banks. It is commonly found and readily colonises sites where the ground has been disturbed, such as recently cleared woodland, or where the vegetation has been burnt. It also colonises areas of land that have been disturbed by clear-felling and by construction projects, being among the first wildflowers to reappear, often in large quantities. Foxgloves are eurytopic plants, as their seeds germinate when exposed to light; for this reason, they are generally absent from shaded areas, such as within woodlands.
''D. purpurea'' is most successful in humus-rich soil, but it can succeed in any soil that isn't too wet nor too dry; either way, the common foxglove only needs a small amount of soil for survival.
Bees use its nectar to make honey.
Larvae of the foxglove pug ('' Eupithecia pulchellata''), a moth, consume the flowers of the common foxglove for food. The caterpillars of this moth crawl into the newly opening flowers, one caterpillar to a flower. It then spins a silken web over the mouth of the flower, sealing it, and then proceeds to feed on the stamens and developing seeds. When the other uninfected flowers fall off, the corolla of the infected flowers remain on the plant, and the caterpillar then pupates in the flower. The species is uncommon, it has been recorded in Britain,[ Germany, Switzerland and Austria.][ Other species of Lepidoptera have been recorded eating the leaves, including '' Mellicta athalia'' and '' Xestia ashworthii'' in Britain, '' Eurodryas aurinia'' in Romania, and '' Mellicta deione'' in Portugal.][
]
Genetics
The colours of the petals of the ''Digitalis purpurea'' are known to be determined by at least three genes that interact with each other.
The M gene determines the production of a purple pigment, a type of anthocyanin. The m gene does not produce this pigment. The D gene is an enhancer of the M gene, and leads it to produce a large amount of the pigment. The d gene does not enhance the M gene, and only a small amount of pigment is produced. Lastly, the W gene causes the pigment be deposited only in some spots, while the w gene allows the pigment to be spread all over the flower.
This combination leads to four phenotypes:
*M/_; W/_; _/_ = a white flower with purple spots;
*m/m; _/_; _/_ = an albino flower with yellow spots;
*M/_; w/w; d/d = a light purple flower;
*M/_; w/w; D/_ = a dark purple flower.
Cultivation
The plant is a popular ornamental, providing height and colour in late spring and early summer. Cultivated forms often show flowers completely surrounding the central spike, in contrast to the wild form, where the flowers only appear on one side. Numerous cultivars have been developed with a range of colours. Seeds are frequently sold as a mixture (e.g. Excelsior hybrids, in shades of white, pink and purple). Some strains are easily grown by the novice gardener, while others are more challenging. They may also be purchased as potted plants in the spring.
''Digitalis purpurea'' is hardy down to (USDA zones 4–9).
Award of garden merit
The following selections have gained the Royal Horticultural Society's Award of Garden Merit:
*Camelot Series:
**'Camelot Cream'
**'Camelot Lavender'
**'Camelot Rose'
**'Camelot White'
*Dalmatian Series:
**'Dalmatian Crème'
**'Dalmatian Peach'
**'Dalmatian Purple'
**'Dalmatian White'
*''D. purpurea'' f. ''alba''
*'Martina'
*'Pam's Choice'
*'The Shirley' (Gloxinioides group)
''Digitalis'' × ''mertonensis'' (the strawberry foxglove)
Toxicity
Due to the presence of the cardiac glycoside digitoxin, the leaves, flowers and seeds of this plant are all poisonous to humans and some animals and can be fatal if ingested.
The main toxins in ''Digitalis'' spp. are the two chemically similar cardiac glycosides: digitoxin and digoxin. Like other cardiac glycosides, these toxins exert their effects by inhibiting the ATPase activity of a complex of transmembrane proteins that form the sodium potassium ATPase pump, ( Na+/K+-ATPase). Inhibition of the Na+/K+-ATPase in turn causes a rise not only in intracellular Na+, but also in calcium, which in turn results in increased force of myocardial muscle contractions. In other words, at precisely the right dosage, ''Digitalis'' toxin can cause the heart to beat more strongly. However, digitoxin, digoxin and several other cardiac glycosides, such as ouabain, have narrow therapeutic windows (i.e., because of their steep dose-response curves, minute increases in the dosage of these drugs can make the difference between an ineffective dose and a fatal one). There are now better options with a wider therapeutic window.
Symptoms of ''Digitalis'' poisoning include a low pulse rate, nausea, vomiting, and uncoordinated contractions of different parts of the heart, leading to cardiac arrest and finally death.
Medicinal use
Extracted from the leaves, this same cardiac glycoside digitoxin is used as a medication for heart failure. Its clinical use was pioneered by William Withering, who recognized it "reduced dropsy", increased urine
Urine is a liquid by-product of metabolism in humans and many other animals. In placental mammals, urine flows from the Kidney (vertebrates), kidneys through the ureters to the urinary bladder and exits the urethra through the penile meatus (mal ...
flow, and had a powerful effect on the heart by making it beat slower but more efficiently waiting for the heart to fill with blood before pumping. During World War II
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
, County Herb Committees were established to collect medicinal herbs when German blockades created shortages; this included ''Digitalis purpurea'' which was used to regulate heartbeat.
Gallery
Image:Digitalis Purpurea.jpg
Image:Digitalis_purpurea_alba_01-Juni.jpg, f.''albiflora''
Image:Fingerborgsblomma, closeup.jpg, Close-up of flower
Image:Foxglove -- Digitalis purpurea.jpg, Close-up of white
Image:Foxglove - Digitalis purpurea.jpg, Close-up of light purple
Image:Digitalis purpurea 'Primrose Carousel' Flower Closeup 1200px.jpg, Flower close-up
Image:Digitalis purpurea 'Primrose Carousel' Leaves 1100px.jpg, Leaves
File: Digitalis seed 2.JPG, Young plant a few weeks old
File:Digitalis_purpurea_004.JPG, Giant flower demonstrating pseudo- peloria
File:Bysedd y cwn ger Solfach - Foxgloves near Solva, Sir Benfro Pembrokeshire, Wales 10.jpg, Detail
See also
* List of poisonous plants
References
Bibliography
Flora Europaea: ''Digitalis purpurea''
Ecological flora of the British Isles: ''Digitalis purpurea''
Purple Foxglove
USDA Invasive Plants of the US
External links
Video footage of peloric Digitalis purpurea
{{Authority control
Biennial plants
purpurea
Garden plants
Medicinal plants of Europe
Plants described in 1753
Taxa named by Carl Linnaeus
Taxobox binomials not recognized by IUCN