Digitalis purpurea L. - Foxglove
FAMILY: Scrophulariaceae—the Figwort Family
This group, also known as the snapdragon family, is a large, cosmopolitan collection of genera that contains many ornamental plants. Within the family apparently only foxglove is toxic.
Flowers are: bisexual, typically irregular, often 2-lipped; stamens: 4, or occasionally 2 or 5; sepals and petals: either 4- or 5-merous; ovary: superior, 2-celled; fruit: a capsule.
PHENOLOGY: Foxglove is a summer-flowering biennial often sold in garden centers already in blossom.
DISTRIBUTION: A cultivated plant, foxglove occasionally escapes and is short-lived in the wild in our range. It would be encountered more often in the flower garden
PLANT CHARACTERISTICS: This plant, native to Europe and northwestern Africa, is easily recognized by its showy, terminal, one-sided racemes of large, drooping flowers. Other characteristics include the basal leaves: in rosettes, lanceolate to ovate, long-petioled; stem leaves: alternate, simple, sessile or nearly so; calyx: 5-parted; corolla: to 7 cm long, purple to pink or white with conspicuous spots inside; stamens: 4.
POISONOUS PARTS: The herbage, both fresh and dried, contains powerful, highly toxic compounds.
SYMPTOMS: In humans toxic reactions include gastric upset, nausea, diarrhea, abdominal pain, severe headache, pulse and cardiac rhythm abnormalities, mental irregularities, drowsiness, tremors, convulsions, and death. In livestock symptoms are similar and include bloody stools, lack of appetite, and the urge to urinate.
POISONOUS PRINCIPLES: Digitalis, an extract of foxglove, has been used medicinally for many years; hence, a large body of information has accumulated concerning it. Physiologically active chemical constituents found in foxglove include digitoxin (0.2-0.4%), digitonin, digitalin, antirhinic acid, digitalosmin, and digitoflavone. The LD50 (oral) for digitoxin in guinea pigs is 60 mg/kg of body weight, and in cats it is 0.18 mg/kg of body weight. The toxins are cardiac or steroid glycosides. The aglycones are derivatives of cyclopenteno-phenanthrene; and the sugars, unusual methyl pentoses. They influence the heart in two ways: stronger cardiac contractions and slower contractions through stimulation of the vagus, prolonging diastole. Digitalis is of much importance to modern medicine.
CONFUSED TAXA: No other garden plants produce tall, (to more than 1.5 m) one-sided racemes of purple, spotted flowers.
SPECIES OF ANIMALS AFFECTED: Humans, usually from drug overdoses, and livestock, from grazing, have been poisoned by foxglove alkaloids. Poisoning in animals can result from hay contamination in addition to browsing fresh material. Susceptible animals include pigs, cattle, horses, and turkeys.
TREATMENT: (l la)(b); (26); (5); (19).