Floral Clock: Telling Time with Flowers

One flower clock tells time by which blooms are open. The other is a working clock planted with thousands of flowers. Both started with real people and real gardens.

Two very different flower clocks

The phrase floral clock covers two quite different things. The first is a botanist's idea: if certain flowers open and close at predictable times of day, a bed of the right species could tell you the hour without any machinery at all.

The second is a piece of civic gardening: a real clock mechanism laid flat in a park, with its dial planted in flowers and its hands sweeping over the beds. You can still visit the one that started it.

Both are charming, and both teach something about time. One shows that plants keep their own daily schedules. The other shows how a city can turn a timekeeper into a garden.

Linnaeus and the horologium florae

The Swedish naturalist Carl Linnaeus described the idea in his book Philosophia Botanica, published in 1751, where he called it a horologium florae, or flower clock. According to the Linnean Society of London, the description appears on pages 274 to 276.

Linnaeus had noticed that the flowers of particular species open and close at consistent times of day, and that these times differ from species to species. Record which flowers are open and which have closed, and you can estimate the time.

He also saw that not every plant is reliable. Some flowers, which he called meteorici, change their timing with the weather, and others, the tropici, shift with the length of the day. Only the aequinoctales, which open and close at fixed hours, are any use for a clock.

Which flowers, and what time?

Uppsala University's Linnaeus Garden publishes the plant list from Philosophia Botanica with Linnaeus's hours. Among the early risers, meadow salsify (Tragopogon pratensis) opens shortly after 3 in the morning, and the dandelion opens shortly after 5 and closes between 8 and 9.

Later in the morning, scarlet pimpernel (Anagallis arvensis) opens at 9, and the ice plant (Mesembryanthemum crystallinum) opens at 10 and closes shortly before 4 in the afternoon. The white water lily (Nymphaea alba) opens shortly after 7 and closes shortly after 5 p.m. Pot marigold (Calendula officinalis) closes shortly after 3 p.m.

Toward evening the list thins out. Linnaeus recorded the Iceland poppy (Papaver nudicaule) closing shortly after 7 p.m. and the orange daylily (Hemerocallis fulva) shortly before 8 p.m. Sow thistle (Sonchus oleraceus), by contrast, opens shortly after 5 in the morning and closes at noon.

Uppsala cautions that the meaning of some of Linnaeus's timing marks is only probable, and many plants on the list have an opening time or a closing time but not both.

Gardeners later found their own time-telling flowers. The Linnean Society notes that the Victorians called the marvel of Peru, a Mirabilis species, the four o'clock plant.

Did anyone ever plant one?

The Linnean Society says Linnaeus probably never planted a floral clock himself. He gathered his timings by observing plants in many different places rather than in one purpose-built bed.

There is also a practical catch. Opening and closing times depend on latitude, and Linnaeus's indicator plants were largely Swedish wildflowers. A list tuned to Swedish summers will not keep the same hours elsewhere. The Linnean Society points gardeners who want to try anyway to a plant list published by the BBC.

For anyone who wants to dig deeper, the Linnean Society points to a detailed English account in F. W. Oliver's 1895 translation of Anton Kerner's The Natural History of Plants, and to Karin Martinsson's Swedish book on the flower clock, which reproduces images of it.

See also: today's daylight hours for your location on OnlineClock.app.

Edinburgh's floral clock, 1903

The planted kind of floral clock is usually traced to Edinburgh. The City of Edinburgh Council calls the clock in West Princes Street Gardens the oldest floral clock in the world, first created in 1903 by John McHattie, then the city's parks superintendent.

Edinburgh's library and museum service, Capital Collections, credits the idea jointly to McHattie and the local clockmaker James Ritchie, and says the clock first ran on the mechanism of a redundant turret clock. Ritchie's firm installed a new mechanism in 1934 and still services the clock.

A local history site, EdinPhoto, drawing on Edinburgh newspapers, gives the start date as 10 June 1903 and says a jeweler named Mossman helped McHattie with the design. At first the clock had only an hour hand, 4 feet 2 inches long. A minute hand followed in 1904.

For decades the clock was wound by hand every day. It was run mechanically until 1972 and converted to electric drive in 1973.

The cuckoo has the messiest history. Capital Collections says a cuckoo that popped out every hour arrived in 1905. EdinPhoto says the 1905 version was only a cuckoo call every 15 minutes, made with organ bellows and pipes, and that a model bird and loudspeaker came later once traffic drowned out the sound. The council dates its cuckoo clock to 1952.

A new design every year

The dial is replanted every year. Since 1946, each design has honored an organization or person, from the Girl Guides Association to Robert Louis Stevenson and the Queen's Golden Jubilee. In its centenary year, 2003, the clock won a gold medal at the RHS Chelsea Flower Show.

The planting has grown over time. EdinPhoto counts about 13,000 plants in the 1930s, 25,000 in the 1950s and 1960s, and around 35,000 by the 1980s. The 2023 design, marking 100 years of the Flying Scotsman locomotive, used more than 50,000 plants of 20 kinds, among them sedum, saxifrage, begonias and geraniums, and it took three gardeners four weeks to plant.

More than a century on, the hands still sweep over the beds every summer. It is one of the few clocks in the world that has to be planted before it can be read.

See also: clocks built for gardens and outdoor spaces on OnlineClock.app.

Keep exploring

Sources

1. March 2013: Linnaeus' Floral Clock - The Linnean Society of London
2. Horologium Florae according to Philosophica botanica, 1751 - Uppsala University
3. Floral clock blooms in honour of 100 years of Flying Scotsman - City of Edinburgh Council
4. Floral Clock, Princes Street Gardens - Capital Collections, Edinburgh Libraries and Museums
5. Princes Street Gardens Floral Clock: background notes - EdinPhoto