Friday, July 24, 2015

The Bells! The Bells!

The largest and smallest species of Campanula in County Durham are flowering in Weardale now.

This is the giant bellflower Campanula latifolia, which graces old hedgerows and woodland edges, and .....

..... this is harebell Campanula rotundifolia, which is often seen at its best in short, dry grassland where its slender stems tremble in the slightest breeze.

It’s worth taking a close look at harebell flowers because they have a really neat fail-safe method of ensuring that they’re pollinated.


When the flower is still in bud the style, with a closed stigma at its tip, is surrounded by five stamens that begin to shed pollen. As the style - which is hairy on the outside- elongates inside the bud it forces its way through the tube of stamens surrounding it, sweeping the pollen from their surface. So when the flower opens it looks like this, and any insect forcing its way down to the bottom of the harebell bell will pick up pollen from the outside of the style. At this stage the flower is functionally male, dispensing pollen.

 Once the pollen is all gone the tip of the style splits into three lobes that curl back and now the flower has effectively become female, ready to receive pollen on one of those three stigma lobes from a visiting insect. But what if no pollen-laden insects turn up? No problem; those stigma lobes just keep curling back until they pick up any residual pollen that’s still left on the outside of the style, so the flower self-pollinates. 

Harebells are quite easy to grow from seed and if you do raise some you’ll see why their Latin name is Campanula rotundifolia, even though the plant has long, grass-like leaves: the leaves in the seedling rosette are indeed rotund.


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