February 20, 2011

Flower power

They may not constitute a host yet, but I've seen my first daffodils in full flower - not an imported or forced bunch in a supermarket, but blooming in a South London front garden.

Daffs are among our earliest spring flowers to come into bloom, and the reasons are twofold. Like crocuses, bluebells and snowdrops, they appear before the trees are in full leaf so as to take advantage of any early spring sunshine before taller plants crowd out the light.

But daffs have also evolved a clever evolutionary trick all of their own, not to do with sunshine, but with bees.

It's February, and cold, and there aren't many pollinating insects about. Those that do emerge early in the year are at real risk from frost, especially during cold nights; if they can't find enough nectar they will weaken and die.

Daffs not only provide a good early source of food, but their yellow trumpets trap sunlight, and by protecting the inside of the flower from air movement can actually generate a microclimate up to 15 degrees warmer than the outside air. This makes them especially attractive to early bumblebees, who will often sleep inside daffodils, emerging covered in pollen which they then unwittingly carry to the next bloom.

Unlike rival bees, who must either wait for the ambient temperature to increase before they can fly, or expend valuable energy vibrating their flight muscles to warm themselves up, bees who have slept in daffodil trumpets can get going straight away, giving them more time to collect nectar at less cost to themselves; and the daffodil ensures its genes are carried on, despite having opened so early in the season. Everyone's a winner.