A biennial, all parts of the plant are poisonous due to glycosides which can slow the heart-rate, this ability is used to advantage in the medicine digitoxin produced from the dried leaves. It prefers a shaded spot which is well-drained such as a hedgebank or the edge of woodland. Flowering occurs from June to September in the second season. A tall spike grows up to 1.5 metres with up to 80 tubular magenta and sometimes white bells which open on one side from the bottom of the spike upwards, these are pollinated by bumble-bees.
If it is allowed to seed the surrounding area will be covered in masses of seedlings for a number of years afterwards, so the fading flower spike or the entire plant must be removed if it has been allowed to bloom. The seedlings are easily uprooted and any remaining roots will not regrow provided the growing point at soil-level is removed. A systemic herbicide such as Glyphosate will work, weedkillers work best in the rosette stage during the first year.

Other plants with similar leaves include Green Alkanet, Comfrey, Tuberous Comfrey and Borage

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