Plants are all around us, so it’s no wonder that crime stories occasionally take advantage of what’s right at hand and make them part of a story. The fascinating history of poisons is just one example, and the history of my favorite poisoner Mithradates Eupator is well worth a read. As a recent post mentioned, analysis of plant matter is a frequent part of crime investigations too—what pollen or bit of plant material is present that shouldn’t be? (Writers of ITV’s Vera frequently include such clues.)

How digested is a victim’s plant-based stomach contents? How did authors use that peat bog (Val McDermid) or giant witch elm (Tana French) to conceal a body? A reader commenting thatRuth Ware’s Turn of the Key was too far-fetched asked, “Whoever heard of a poison garden?” This is a person who doesn’t know her Nathaniel Hawthorne. “Rappaccini’s Daughter” is one of my favorite Hawthorne stories! (Maybe the commenter knows her Marvel Comics heir, Monica Rappaccini.)

There’s another side to planting plant evidence too. Rather than obscuring the method, timing, and place of a crime, plants can be used proactively, to send a message, not hide it. Vanessa Diffenbaugh’s novel The Language of Flowers takes on this topic explicitly, and a young couple lets specific flowers say what they are reluctant to express directly. (How Victorian!) As one reviewer said, it’s “a captivating novel in which a single sprig of rosemary speaks louder than words.”

For a tutorial on the practice of floriography, remnants of which have survived thousands of years, Amazon has at least two well received books (The Complete Language of Flowers and Floriography), neither of which I’ve read. Both are well illustrated, though some others are not, which is a big disadvantage when you want to see whatever it is so you can describe it.

Online sources helped me decide which flowers a character deeply sorry about the way he’d treated his late wife and son should choose. He took pale pink roses to his wife’s grave and to their son’s, asphodel, the flower of regret.

Roses have many meanings including as a symbol for silence or secrecy (“sub rosa”) dating to the myths of ancient Greece. Red roses are associated with both courage and romantic love. Yellow roses, aside from the Texas association, symbolize friendship and new beginnings. White roses are linked to innocence and purity, explaining their frequent appearance in bridal bouquets. Pale pink roses, as in my story, are linked to sympathy. Have one character give another a black rose and you’ve sent a message.

Floriography has been practiced for thousands of years, and even though your readers may not know the details, carefully selecting which flowers you use in a story adds emotional resonance, and for the cognoscenti, a grace note of delight. Authors from Shakespeare to J.K. Rowling have used flowers in this way. Ophelia’s flowers included rosemary (remembrance), pansies (thoughts), fennel (sorrow), columbines (affection), and daisies (innocence and purity). New meanings keep being added to our store of floriography too. One of the most compelling of recent years was London’s public art installation to commemorate the outbreak of World War I. Each of the 888,246 red ceramic poppies represented a British or colonial service member who died in the Great War. If you study the pictures, you’ll never forget the association.