Horologium Florae
From Wikipedia:
The flower clock was a garden plan hypothesized by Carl Linnaeus that would take advantage of several plants that open or close their flowers at particular times of the day to accurately indicate the time. According to Linnaeus’s autobiographical notes, he discovered and developed the floral clock in 1748. He proposed the concept in his 1751 publication Philosophia Botanica, calling it the Horologium Florae (lit. "flower clock").
