more poisonous flowers for oyceter

Previously mentioned elsewhere: datura (by jonquil, named for a toxic flower herself), Brugmansia, Brunfelsia nitida. (All Solanaceae really, though tobacco might have other interesting implications as well.)

Thought of today:
Buttercups. But is bloody diarrhea really ever what you want to associate with your character?
Foxglove. Death by excessive cardiac excitation? Check.
Apocynum androsaemifolium. Smells wonderful.
Black locust. Also smells divine, and is blooming right now -- but is an invasive weed where I live. I haven't yet tried the black-locust honey I got from the Madison farmer's market.

Found via links from previous:
Lily of the valley.
Sweet pea. If Georgia O'Keefe didn't paint that photo, she should have.
Lobelia.
Wisteria. A sweet twining vine that can pull your house down. But see also Fuji Musume.
Larkspur.
Rhododendron. Apocryphally, even its honey can cause delirium. Lots of interesting species with different looks.
Gelsemium sempervirens.
Golden-chain.
Oleander.