Most azaleas drop their flowers. What happens some times is that petal blight gets into the flower before it drops and causes it to turn to mush and become unsightly. Petal blight is most noticeable on later blooming flowers. Early blooming plants are seldom hit. It takes a while for it to get going each year. The best protection is proper sanitation; that is removing all spent flowers. This delays the onset of the disease. Once it starts to attack, then there are sprays that are approved to keep the disease at bay. It is worst when the flowering season is accompanied by frequent wet conditions. The sprays are also least effective when there is frequent rain, one of those gotcha situations.

Here is a link that might be useful: Ovulinia petal blight

in my experience, the kurume hybrids and those azaleas with small individual flowers are worse at holding onto the spent, brown flowers than azaleas in some other groups. also, i think the leaf size and arrangement on these contributes to this trait.
'coral bells' is probably the worse one for doing this that i grow. i sometimes wait for a dry, sunny day and get out the broom to knock them off.
the southern indicas seem to be more self-cleaning because they have larger flowers and are not clustered in tight groups. they are good azaleas for your area, too.
look for 'mrs. g.g. gerbing' in white - could be easier to find than 'h.h. hume'. nice fragrance to that one too but it will grow large. possibly the most popular and beautiful of this group is 'george l. taber' with pink/purple colorings.

My Southern Indicas do, indeed, drop their spent flowers. I have both George Tabor and Mrs. Gerbing, along with lavender and red Formosas and Southern Charm. I didn't notice the fragrance of Mrs. G., and I guess I'll have to wait until next year, since my azaleas have come and gone for this year. The worst culprit in my yard for hanging onto the old blossoms is Fashion, but I can forgive it, since it blooms with abandon. I just brought back a tiny plant of Coral Bells from SC in my carry-on luggage, so I guess I'll be picking the dead flowers off of it before long, too.

I agree that most of your trouble with the brown dregs of the blooms hanging on may be due to petal blight. We spray as the buds are about to open and unless there are several days of dreary rainy/misty days, that solves the problem for the year. Sometimes, if it has been very wet, we will spray again to get the late blooming ones. A blight free bush will drop it's blossoms intact.

It seems to be the intense daytime heat that does our Florida azaleas' flower's in. I notice that the pink formosa hold the bloom much better than my red ruffle's do. The flowers all look beautiful in the morning then start to just melt by mid-afternoon. Especially if I forget to give a thorough watering in the morning. My George Tabor seem to fall somewhere in between the incredibly hardy Formosa and the less heat tolerant "red ruffle". I havent tried to grow a full white azalea yet, but I would love to break up the huge swaths of pink in the spring as I am going to make azaleas the central theme in my permanent plantings. Let us know here and in the Florida forums on how the white azaleas do for you.

The white azaleas that I bought labeled 'Delaware Valley White' turned out to be a little hose in hose that hangs on to those 'used tissues' forever. I tried again with something 'H.H. Hume' which turned out to be very similar to the first one. I'm going to buy from a more reliable source next try and wait until they're in bloom.

'George Tabor' is a lovely sport of 'Formosa' and is a great performer here and good companion for the darker pinks. 'Pink Ruffles' is my favorite and it tolerates the heat pretty well.

A good 'breaker' if you have lots of room is spirea or the viburnum known as 'snowball bush' in the south. Dogwoods make a second story cloud of white that is breath-taking, too.

Nell

h h hume is a cross with SNOW. Snow is notorious for brown spent tissue looking flowers on the shrub. I too am searching to find more information specific to H H Hume