The tall spires of Digitalis purpurea, the common foxglove are now making an appearance in the garden. This is an herbaceous biennial which produces a tight rosette of leaves in its first year and a flowering stem in the second. This is typically 1 to 2 metres tall with flowers arranged in a showy, terminal, elongated cluster, each flower being tubular and pendent. These are typically purple but may be pink or white. The inside surface of the flower tube is heavily spotted. The plant is frequented by bees which climb right inside the flower tube to reach the nectar within.
It is native to this country and widestread throughout most of temperate Europe. The generic name Digitalis comes from the Latin for finger (digitus) referring to the shape of the flowers. The plants are well known as the original source of digitoxin used to produce the drug digoxin.This has been used as a heart stimulant since 1785. Due to the presence of this cardiac gylcoside, the leaves, flowers and seeds of this plant are all poisonous to humans and some animals and can be fatal if ingested. With correct dosage however, the digoxin is useful as a mediction for heart failure causing the heart to beat more strongly. It does have a very steep dose-response curve meaning that minute increases in the dosage of this drug can make the difference between an ineffective dose and a fatal one.
Today digoxin is normally made from the leaves of another species, Digitalis lanata. However, during the Second World War D.purpurea seeds were collected from the wild and grown to produce large quantities of leaves for medicinal use.