Digitalis

Digitalis

Foxgloves

Genus:	Digitalis
Family:	Scrophulariaceae
Pollination:	Insects, also visited by hummingbirds

Digitalis is a genus of about 20 species of herbaceous biennials, perennials and shrubs that was traditionally placed in the figwort family Scrophulariaceae, but following new genetic research has now been placed in the much enlarged family Plantaginaceae. The genus is native to Europe, western and central Asia and northwestern Africa.

The members of this genus are known in English as foxgloves. The scientific name means "finger-like", and refers to the ease which a flower of Digitalis purpurea can be fitted over a human fingertip. "Foxglove" has a similar origin as a corruption of "folk's glove", referring to the fairy folk.

Foxgloves are grown for their showy flowers and long period of bloom, but they are highly toxic, so care needs to be taken when growing where children or pets are present.

Description

The flowers are produced on a tall spikes or racemes, tubular with 2 lips, and vary in colour with species, from purple to pink, white and yellow. Leaves are in basal rosettes and also alternate on the stem, simple with slightly toothed margins.

Growing conditions

Full sun with a rich soil. Short-lived, but self seed readily in good soils.

Species

Uses

Foxgloves can be used for cut flowers, however due to the toxicity this may be inappropriate for homes with cats or children.

Digitalis is also the name of a group of drugs (digitalis glycosides) derived from the plant. This is a classic example of an active ingredient formerly used by folklorists and herbalists, now having being identified, purified and used in mainstream medicine. Herbalists have largely abandoned its use because of its narrow therapeutic index and the difficulty of determining the amount of active drug in herbal preparations. Digitalis was initially employed empirically for a variety of purposes, including the treatment of epilepsy and other disorders. Its use is now confined to treating heart problems (mainly regulating the pulse) as it is ineffective in those other conditions.

Toxicity

Depending on the species, the digitalis plant may contain several deadly physiological and chemically related cardiac and steroidal glycosides. Thus, the digitalis has earned several more sinister monikers: "Dead Man’s Bells", and "Witches’ Gloves".

The entire plant is a poison (including the roots and seeds), although the leaves of the upper stem are particularly potent, with just a nibble being enough to potentially cause death. Early symptoms of ingestion include nausea, vomiting, anorexia, diarrhea, abdominal pain, wild hallucinations, delirium, and severe headache. Depending on the severity of the toxicosis the victim may later suffer irregular and slow pulse, tremors, various cerebral disturbances, especially of a visual nature (unusual color visions with objects appearing yellowish to green, and blue halos around lights), convulsions, and deadly disturbances of the heart.

There have been instances of people confusing digitalis with the harmless Symphytum (comphrey) plant (which is often brewed into a tea) with fatal consequences. Other fatal accidents involve children drinking the water in a vase containing digitalis plants. Drying does not reduce the toxicity of the plant. The plant is toxic to animals including all classes of livestock, as well as cats and dogs.

Maintenance

Propagation

Plants tend to reseed prolifically in the garden, but are also easy in flats.

Harvest

Flowers are good for the vase, but water should be changed and disposed of regularly.

Pests and diseases

Pests

Aphids

Foxglove Aphid: Acrythosiphon solani
Crescent Marked Lily Aphid: Neomyzus circumflexus

Mealybugs

Mealybug: Pseudococcus fragilis
Long-tailed Mealybug: Pseudococcus longispinus

Beetles

Japanese Beetle: Popillia japonica
Asiatic Garden Beetle: Maladerma castanea
Rose Chafer: Macrodactylus subspinosus

Caterpillars

w:Foxglove Pug (on flowers)
w:Lesser Yellow Underwing (on leaves)

Diseases

Anthracnose

Colletotrichum fuscum

Leaf Spot

Root and Stem Rots

Wilts

Verticillium albo-atrum

Tobacco Mosaic Virus

Beet Curly Top Virus

Stem and Bulb Nematode: Ditylenchus dispaci

Gallery

Digitalis ciliata
Digitalis grandiflora
Digitalis lutea
Digitalis purpurea illustration from Köhler's Medicinal Plants
Digitalis purpurea
Digitalis purpurea
Digitalis purpurea
Digitalis purpurea var. alba

References

Wikimedia Commons has media related to: Digitalis

Flora Europaea: Digitalis species list
Flora of Turkey. Edinburgh University Press.
Molecule of the Month - Digitalis
eMedicine link
Grecian Foxglove USDA Noxious Weed List.
Purple Foxglove USDA Noxious Weed List.
Richard B. Silverman, The Organic Chemistry of Drug Design and Drug Action.
Ann Fowler Rhoads and Timothy A. Block (2000). The Plants of Pennsylvania: An Illustrated Manual. Anna Anisko, illustrator. Morris Arboretum, University of Pennsylvania Press. p. 667.
P. D. Strausbaugh and Earl L. Core (1977). Flora of West Virginia (Second ed.). Seneca Books, Grantsville, W. Virginia.
Christopher Brickell and Judith D. Zuk (1997). The American Horticultural Society A-Z Encyclopedia of Garden Plants. DK Publishing. pp. 367–368.
Staff of the L. H. Bailey Hortorium (1976). Hortus Third: A Concise Dictionary of Plants Cultivated in the United States and Canada. Cornell University Press. pp. 385–386.
Pirone, Pascal P. (1978). Diseases & Pests of Ornamental Plants (Fifth Edition ed.). John Wiley & Sons, New York. pp. 243–244. {{cite book}}: |edition= has extra text (help)
Cranshaw, Whitney (2004). Garden Insects of North America: The Ultimate Guide to Backyard Bugs. Princeton University Press. p. 318.