The sun was mankind’s first clock, but reading it has not always been restricted to sundials and shadows. For centuries humanity has also been divining time, if inexactly, by the opening and closing of flowers. The idea of a “flower clock” was first codified by Carolus Linnaeus, the Swiss botanist, in 1751. (See? Even the botanists in Switzerland are obsessed with time.)
Linnaeus observed that certain individual species of flowers open and close their petals at specific points in the day: catmint between 6 and 7A.M., hawkweed between 7 and 8A.M., marigolds at 9A.M. and so on. He found the opening and closing of these flowers to be so regular that he conceived the creation of a circular garden that would be arranged like a clock face, with 12 segments of flowers grouped by the time they open and close. (Catmint occupying the space between 6A.M. and 7A.M., etc…)
In this way, you could see what time it was just by looking at your garden and seeing which group of flowers was drinking in the sun. This method of telling time, in good weather conditions, was accurate to within a half hour.
Though Linnaeus was the first to set down his botanical discoveries via the scientific method, the idea of a flower clock garden pre-dates him considerably. In fact, Andrew Marvell described a floral clock in his poem “The Garden” in 1678.
“How well the skilful gardener drew
Of flow'rs and herbs this dial new;
Where from above the milder sun
Does through a fragrant zodiac run;
And, as it works, th' industrious bee
Computes its time as well as we.
How could such sweet and wholesome hours
Be reckoned but with herbs and flow'rs!”
Source articles: http://www.newscientist.com/backpage.ns?id=mg19526112.700
http://www.bbc.co.uk/dna/h2g2/A5170024
