digitalis purpurea

foxglove, introduced from europe -- naturalised from garden flowers. very toxic; contains cardiac and steroidal glycosides. which lead it to be a valuable source of arrhythmia-controlling medicines, but determining the precise amount of the active drug present in gathered plants isn't possible for an herbalist, and small errors in dosage can be deadly -- making it unwise for people like me to self-medicate with it.