Close up of the centre of a yellow nasturtium flower (family Tropaeolum).

Exploring the details and intricacies of nature, afforded to us by the wonders of macro photography, often throws up more questions than it answers. For example, looking closely at the centre of a nasturtium flower makes you wonder why it has a ‘fringe’ at the entrance to it’s trumpet?

Is it just for decoration? This is unlikely; although we like to think of beautiful flowers growing in abundance are purely for our enjoyment, there’s a biological reason for each and every part, the primary function of the flower as a whole, being to attract pollinators to fertilize the plant’s seeds and continue another generation.

Each individual part of the flower must have it’s own specific purpose, for example, the dark orange markings on each petal serve as ‘arrows’ directing birds and insects to the nectar they’re in search of and consequently to the flower’s pollen. Interestingly, the two upper petals have much stronger coloured markings, indicating ‘this way up’. This is important for a humming bird, a regular nasturtium pollinator in some parts of the world, as nectar collects at the end of long spur to the rear of the flower and a humming bird’s beak only curves one way.

Some orchid flowers mimic the female of a particular insect, thus attracting males who cover themselves in pollen while attempting to mate with the imitated female. Nasturtiums are pollinated by a variety of birds and insects, so a masquerading as a mate doesn’t fit our nasturtiums’ fringe.

There are tropical plants that alter their physical attributes to trap an insect, by making it’s interior slippery, for example. Once the plant releases pollen and covers the insect, it’s surface changes texture to one which the bug can grip and free itself. The nasturtiums fringe doesn’t change texture, and neither does it have the ability to trap an insect inside the flower.

So, does the fringe protect the flower’s precious pollen-laden anthers? The nasturtium doesn’t want to be protected from birds or insects; quite the reverse, it needs creatures to visit. Perhaps then, the fringe collects pollen grains loosened by high winds and deposits them on visitors as they brush against the fringe on entering or leaving the flower.

If you have any theories on why the nasturtium flower has a fringe, I’d love to hear about them!

Exif Data
Focal Length: 4.1mm; Exposure Time: 1/100 sec; Flash: Off;
F-Number: F/3.5; ISO: 80; Metering Mode: Spot;