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 widespread
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 medication 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.