Digitalis purpurea (& sp.)
An extremely common tall, upright perennial, up to 1.5m. Easily recognisable by its beautiful purple/pink bell shaped flowers hanging from a central spike. White and yellow flowered strains are not uncommon. Anyone picking spring leaves, especially comfrey or wild garlic, should be able to recognise this plant by its basal leaves alone. They are thick, soft, hairy, shallowly serrated, with noticeable veins, often purple, arranged around a central stem. Not really like wild garlic at all, but I have seen people with young children indiscriminately picking it, and reckon its a nasty accident waiting to happen. 2 leaves can contain sufficient cardiac and steroidal glycocides to cause severe hallucination, nausea, headache and raise or lower your heart rate rate to fatal levels. Even handling of the leaves has been found to cause measurable fluctuations in heart rates. You have been warned!
For more discussion on toxic plants and fungi see “The Day I Ate a Deadly Plant: The Spectrum of Edibility”