Tim Brinkhof at JSTOR Daily:
Sad Cypress is hardly the only murder mystery to revolve around a flower. As writer and landscape historian Marta McDowell observes in her new book, Gardening Can Be Murder: How Poisonous Poppies, Sinister Shovels, and Grim Gardens Have Inspired Mystery Writers, gardens are popular settings in crime and detective stories, especially those published in the late nineteenth and early twentieth centuries. The mysterious people that tend to them also feature commonly in these stories. Sometimes they’re the victims, sometimes the killers, sometimes the unlikely heroes who save the day. Gardens invariably lend setting, motivation, and symbolism. On occasion, as in Sad Cypress, gardening even provides the all-important clues to solving the crime.
Like those clues, the link between homicide and horticulture isn’t obvious. As a literary genre, murder mysteries matured during the Industrial Revolution, when rural villages turned into smog-covered suburbs replete with seedy establishments and dodgy alleyways.
more here.