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Friday, March 16, 2012

Rhododendron dauricum, Ericaceae

I'm not a great fan of some of the overblown garden hybrid Rhododendrons but Rhododendron dauricum is always a welcome sight. It's an early bloomer - not surprising when you look at its natural geographical distribution, across northern Russia, China and Japan - and it has been flowering in my garden since the beginning of March.

The fact that it flowers on almost bare twigs enhances its beauty and no doubt ...

.... makes it more conspicuous to the first queen bees that emerge in spring from hibernation to collect nectar from the flowers. This Rhododendron species and many others in the genus have a particularly unusual way of dispensing pollen to visiting insects.

In many plants the anthers at the tip of the stamens simply burst open and expose all their pollen at once, but R.dauricum anthers dehisce through a small pore at the tip - which you can see clearly in the lower-most anther in this picture. The buzz of bees visiting the flowers makes the stamen filaments vibrate with a similarly high frequency, shaking pollen out of the pore a little at a time - which is an economical way of distributing the available pollen to as many bumblebee visitors as possible during the long flowering period in spring.