Can you help me identify a tall blue fall flower?

Q:  There is a very tall, intensely blue perennial I have noticed blooming in a few late fall gardens in my neighborhood.  Can you help me identify it?  It seems to do well in sun or shade.

A:  This is a tough one, and please correct us if we are wrong, but if the picture here matches your “mystery plant,” it is “Aconitum, also known as ‘the queen of poisons,’ aconite, monkshood, wolf’s bane, leopard’s bane, women’s bane, devil’s helmet or blue rocket, is a genus of over 250 species of flowering plants belonging to the family Ranunculaceae,”  according to our sources.  Some species in this family have poisonous or medicinal properties.  It is truly striking in the fall border!  Questions about plant identification may also be directed to the Bartlett Arboretum Plant Clinic in Stamford CT – just send an email to