Flower Clock

On this first day of the year that is longer (the day after the winter solstice), I’m thinking of time. Recently I heard of an idea for a living clock. Carolus Linnaeus (1707-1778), the biologist who developed the two-word naming system for biology, noticed that plants opened and closed their flowers at predictable times during the day and night. In other words, plants, like animals, have internal biological clocks.

For example, Goat’s Beard (Tragopogon pratensis) flowers open at 3 am, while Dandelion (Taraxacum officinale) flowers open at 5 am. Linnaeus realized that you could tell time by looking at which plants’ flowers were open. After researching and planting a wide variety of plants, he was able to tell time to within a half hour, just by observing his flowers. Linnaeus drew a diagram of a plant clock, but it appears he never actually planted one.

I think this would be a lot of fun to try. This article has a diagram with plants that grow here in North America, like morning glories (open at 10 am) and California poppy (open at 1 pm). This article has information about making your own garden, as does this, and both have a list of many plants and their flowering time.

I haven’t been able to find photos of anyone who has successfully planted a living clock, so if you know of any please let me know! Supposedly there is one at the University of Uppsala, in Sweden, where Linnaeus lived, but I haven’t been able to find photos of it. They do have a “Linnaeus garden” in their botanical gardens.