Helleborus, which can cause tinnitus, vertigo, stupor, thirst, a feeling of suffocation, swelling of the tongue and throat, emesis (vomiting), and catharsis, bradycardia (slowing of the heart rate), and finally collapse and death from cardiac arrest. Pretty though.
Euphorbia polychroma: An undemanding perennial, Euphorbia polychroma offers a pleasing contrast of colors on a neat, almost architectural form. It grows to about 15in and produces a splendid show in May from bright yellow bracts. Their color is long lasting, but changes to rose-bronze as they age above the green foliage. A sensational ground cover plant or accent in a sunny garden. Quite tolerant of hot, dry conditions (but not the heat and humidity of the South).