In article ,
Emrys Davies wrote:

It is quite likely that the roots of the shrub are too dry during the
late summer when the flower buds form.

Encourage your friend to keep its roots moist during the growing season
and its performance should improve.

Yes, but she did say that it formed buds which didn't open!

I don't grow rhododendrons (obviously), but I have quite a few plants
that form buds only to have them swell, shrivel and drop off. The
causes are usually some combination of very dry conditions, a late
frost, or a dry or cold period with a wind.

Stornoway (to refer to another poster) isn't known for dry winds,
or even very cold ones. High up on the Lanarck moors, I would expect
that a cold wind just as the buds start to swell or open is the cause.
Many flower buds are much frost hardier when small than as they start
to become flowers.



Regards,
Nick Maclaren.