Nick Baker’s hidden Britain
Reveals a fascinating world of wildlife that we often overlook.
The mechanics of the lesser celandine
Early spring can be a tedious thing, with seemingly endless bleak days. Our eyes hunger for a splash of colour and the lesser celandine, Ficaria verna, provides it – turning hedgerows and woodland banks golden with constellations of their bright starry flowers; terrestrial sunshine thrown up at us from their lowly spot.
Few of us talk of celandines as harbingers of the warmer season ahead – we seem to prefer the daffodil. Maybe it’s their omnipresence or their somewhat unfair reputation as a weed that takes off the edge. Whatever the reason, celandines are worth a closer look.
They come in four different subspecies and occasionally produce rare double blooms, while petal counts vary from six to 13. And the variety doesn’t stop there. The heart-shaped leaves differ in size, and while most form glossy, dark green masses, in some populations they’re washed with silver or gold tidemarks, like cyclamen.
But there is another quality – one moment a glorious carpet of eye-searing yellow, then they’ve gone, only to return again the next day, as if turned on and off by a switch. Initially, I thought that the colony at the end of my garden was so floriferous that those that died were simply replaced the next day by new blooms. However, a small ribbon tied around the stem of one flower revealed the truth – they open and close.
The petals are spread to the heavens during the day, and close tight like a fist again in the late afternoon – but then on some days they don’t open at all.
This botanical ‘hide and seek’ is something that goes by the brilliant name of ‘nyctinasity’. The mechanism behind this sleight of hand has been much debated, and the specifics for our celandine are still a bit of a mystery, but it seems that a differential swelling of cells at the base of the petals are the basis of the mechanics of this. The plant increases the concentration of sugars in these specific cells, and in doing so, by a process of osmosis, water is drawn into the cell and it expands.
So, if cells on the inner surface of the petal swell quicker than those on the outer surface, the petal is bent away from the centre of the flower and, as a collective expression of this, the flower opens.
But how is this triggered? A change in temperature of 3–5 degrees seems to be the magic number, so as the spring air warms up, the flowers open and this reverses as the air cools in the evening.
Hot and cold
Because it’s the change in temperature that is critical, it explains why those that flower later in the season still pulse to the rhythm of the day and don’t just remain open.
However, flowers on a cold day, when the temperature doesn’t change much until later in the afternoon, are less likely to open even if the temperature does increase by the few degrees that would have triggered the action earlier in the day. This points to an internal clock that ticks away in the background and has further influence on flowering.
Still, the question remains: why not just keep them open all the time? Well, maybe to avoid weather damage, protect their pollen powder, and avoid predation by slugs, deer and other animals.