Linnaeus' floral clock on the island of Mainau

As you may have noticed, I am quite fascinated with the earliest beginnings of my scientific discipline, which was almost entirely involving research on plants. The most famous story from that early period is the construction of a Flower Clock by Karl Linne, the father of taxonomy.

So, of course I got really exited when I saw, on the Mainau island last Friday, a reconstructed Linnaeus' floral clock.

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Then I looked carefully - and noticed it was not telling the correct time. This was taken at 3pm.

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So I thought about it for a second....and, well, this is what I think is going on here.

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First, Linnaeus' clock is a 12-hour clock, not a 24-hour one. It does not include plants that flower at night. The division of the daytime into 12 hours makes sense only during the equinox. As daylength changes during the year, each hour will become gradually longer than 60 minutes for six months, then shorter then 60 minutes for six months. Thus, such a clock will not be precise on any day except the (spring) equinox.

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Second, the latitude of Mainau in Germany is different from that in Upsalla in Sweden. And yet, the same species of flowers were used in both places. Thus, the photoperiod will be different and plants will flower at different times of day at these two places (again, except on the day of spring equinox).

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Very pretty - but not a precise time-piece....

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