Rhodedendron

In fact Rhododendron prefer acidic soil - perhaps it's not acid enough? You might need to use an acidifier.

The BBC has advice: http://www.bbc.co.uk/gardening/plants/plantprofile_rhododendron.shtml

... from which I garner:
- Pruning is not usually required, but it it's straggly it could be worth doing.
- Dead heading might help you get more flowers
- Careful with soil improvers, tap water etc. that might lower the acidity of the soil.

Hola

Rhododendron thrive only in an acid soil that is moist but well drained. Their fibrous root system appreciates a relatively loose, friable soil that the roots can easily penetrate.

Most Rhododendrons need no pruning, but old or straggly specimens benefit from a cut back. The best times to prune are late winter, especially for late flowering plants, or just after flowering.

As a rule, smooth barked rhododendrons - mostly species - do not respond well to being cut back but the commoner hybrids do. Carry out sever pruning in two or three stages, leaving some foliage each time. Remove the thick branches first and, if these put out new growth, cut back or remove altogether the thinner branches.

Most small leaved species and hybrids can be trimmed after flowering to maintain a compact shape, without loss of flowering. Most deciduous azaleas can be invigorated or reduced in size by pruning - it is the azalea that we have in our garden :)

Hope that helps and happy gardening

I assume you are refering to the rhododendron with large broad
shiny leaves which form their buds in fall and bloom in spring.
These plants need acid soil and should be pruned after flowering
so as not to destroy the blooms for next spring. Because of a
hard freeze in April 2007 followed by drought in summer , one of
my rhodos died and the another one, about 5 ft. tall, has some
blooms but is about half dead (w/o leaves). I am planning on
pruning it to some extent. There are new shoots coming up from the ground several inches from the main trunk and I may go only with
these. Generally, these shrubs are in flower maybe 3 weeks, but it depends on the climate of course. I am in z6 and that is about what they do here.
Azaleas, which are technically rhodos, are smaller leaved and carry their buds from the previous fall & are in bloom about the same amt of time.
Evergreen azaleas from further s may be different.