Kent,
United Kingdom 
We have a beautifity rhodedendron but last year although it was full of gorgeour fat buds, after the winter, every bud had completely disappeared. Any clues? We have blamed everything from the weather to squirrels or birds. Help
6 Sep, 2010
Rhodies can be susceptible to a disease known as bud blast.
The buds will stop swelling and turn brown, and be covered in brown prickly growth.
However I believe that your problem was more likely to have been caused by the severe cold we had last winter.
Most of our Rhodies in this country are hybrids, and have differing levels of hardiness, usually between H3 - H5, H3 is hardy in a sheltered site in most of the UK, good down to -17.5 oC but may be damaged by severe winters.
If you suspect frost and your Rhody has buds set, cover with a garden fleece on the coldest nights.
If the buds turn brown and stop developing, it could well be that they have been frosted.
11 Sep, 2010