Are you living on Flower Time?

Photo image of two Evening Primrose flowers opening.

Anyone who’s dipped into horticultural history, will know the name of Carl Linnaeus. He was an 18th century Swedish naturalist most famous for classifying all minerals, plants and animals known at that time. You’d think he’d want a long lie down after that, but no – he went on to establish the use of binomial nomenclature for plants which had previously been a bit of a free-for-all. Linnaeus’ work Species Plantarum was the foundation on which present day plant nomenclature has been built.

So when you’re learning Genus + species + ‘Variety’ for your horticultural exams, you have Linnaeus to thank (honestly, it would have been a whole lot harder without his system).

What’s this got to do with flowers specifically?

In Philosophia Botanica Linnaeus identified and listed three types of flowers:

Meteorici – those which change their opening and closing times according to the weather conditions),

Tropici – those which change their times for opening and closing according to the length of the day), and

Aequinoctales  – those which have fixed times for opening and closing (regardless of the length of day or weather conditions). For example, Star of Bethlehem is an Aequinoctale, so if you hang around to watch it open, you’ll know that it’s (roughly) 11am.

Above left: Illustrated Horologium florae Above right: Star of Bethlehem (Ornithogalum umbellatum)

The unique attribute of Aequinoctales to reliably open and close their petals, led to them being incorporated into a ‘flower clock’.  This BBC webpage lists approximate flower opening and closing times for various Aequinoctales.  If you plant these clockwise in the order in which they open their petals, you get a type of natural clock. Good, eh?  Linnaeus listed 46 examples of flowering plants that open at certain times of the day, he arranged 43 of them in time sequence, from 3am to 8pm, to produce what he called his Horologium florae, or flower clock (see image).

There’s more on this, including some lovely illustrated flower clocks in this article from Country Life.

Do let us know if you try reproducing a flower clock next year and what results you get!

Roz

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