Three prominent vertical forms cover much of the land at Stoneworld on Galiano Island, BC: megaliths, stinging nettles and purple foxgloves. The latter two are clearly avoided by the sheep inhabiting the grounds, and with good reason; the stinging nettles, I assume, would cause blistering, whereas the foxglove is simply (potentially) fatal.
The species is similarly poisonous to humans, though in low and measured doses it is used to treat heart failure. The Plants for a Future factsheet for Digitalis purpurea points out the need for extreme caution: “Great care should be exercised in the use of this plant, the therapeutic dose is very close to the lethal dose” . Not a plant to be trifled with! Wikipedia provides a good summary of Digitalis purpurea / Digitalis and the associated cardiac glycosides digitoxin and digoxin.
Despite its potential to poison, it remains a popular garden ornamental. An introduced plant to western and eastern North America (where it can be a common sight), I suspect its spread is due to escapees from home gardens. The species is native to much of Europe.