Floral Clock

Floral Clock by Linneaus’ 

Floral Clock – A quick glance at the Linneaus Society of London website gives a brief explanation.

“Carl Linnaeus observed over a number of years that certain plants consistently opened and closed their flowers at particular times of the day, these times varying from species to species. He concluded that one could deduce the approximate time of day according to which species had opened or closed their flowers. Arranged in sequence of flowering over the day they constituted a kind of floral clock or “horologium florae”, as Linnaeus called it in his Philosophia Botanica (1751, pages 274-276).”

Linnaeus identified two groups of flowers for his floral clock:

Those that vary their opening and closing due to external conditions: both Meteorici – those that vary their opening and closing times, in response to the weather and Tropici – those that vary their opening times according to the length of the days.

Flowers that have fixed times for opening and closing (Aequinoctales).  It is this group of flowers that are required for a floral clock.

The idea that certain flowers bloom at certain times of day may be familiar but in reality flowers have a sophisticated inner clock which is so accurate that we can indeed rely on flowers to tell us what the time is.

Ever since Linnaeus first wrote about the concept of a Floral Clock in 18th century, many gardeners have tried to produce their own version of a garden where the flowers were arranged to that they would flower successively, announcing the time of day as they did so.  Linneaus probably never actually constructed his clock. Those who have tried to emulate him have two main hurdles to overcome – firstly many of his chosen plants were native Swedish wildflowers and their opening/closing times depend on latitude.

Floral Clocks were a 19th Century craze – the idea being to plant a circular bed with twelve sections.

The plants in each section would flower in sequence.

If you are tempted to try to construct such a display – have a look at the plant list below:
2:00 AM                 Night blooming cereus closes
5:00                        Wild roses and (the obvious) morning glories,
6:00                        Spotted cat’s ear, catmint
7:00                        African marigold, orange hawkweed, dandelions
8:00                        Mouse-ear hawkweed, African daisies
9:00                        Field marigold, gentians, prickly sow thistle closes
10:00                      Helichrysum, Californium poppy

11:00                      Star of Bethlehem
12:00 Noon            Passion flower, goats beard, morning glory closes
1:00 PM                 Chiding pink closes
2:00                        Scarlet pimpernel closes
3:00                        Hawkbit closes
4:00                        Four o’clock (Mirabilis’ Marvel of Peru) opens, Californian poppy closes
5:00                        White water lily closes
6:00                        Evening primrose, moonflower
7:00                        Difficult
8:00                        Daylilies and dandelions close
9:00                        Night blooming cereus
Ok, so you’ve invested in the show-stopping 12-seater extending aluminium garden table and your patio look is complete with its rattan sun loungers, now all you need is a Flower Clock.

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