The term 'Poisonous Flower' can be broken down into two crossword solutions: Wolfsbane and ARUM. Wolfsbane, also known as Aconitum, is a genus of flowering plants in the buttercup family that are highly toxic and have been used as a poison since ancient times. ARUM, also known as Araceae, is a family of flowering plants that includes many species of poisonous flowers, such as the Calla Lily and Jack-in-the-Pulpit.