A fall or even into early winter rebloom is not uncommon for any number of rhodies - the reasons why are unclear, although there is thought that day length and temperatures stimulate already formed flowerbuds into opening by mimicking the conditions under which they would normally bloom in spring. And out of season blooms can also be stimulated by stress. How consistent this is is pretty variable - it would not be a primary trait I'd purchase for, as there is no real guarantee it would necessarily happen again. Some hybrids and species may be more prone to this phenomenon than others, giving rise to breeding programs for repeat bloomers, like the Encore azaleas.

Not many. However many rhododendrons are tricked into fall blooming. This is considered a fault in most cases because it gives a lousy bloom in the fall and spoils the buds which start to open so they don't bloom in the spring.

Some exceptions are:

Better Half (probably Elizabeth hybrid) EM, -5F, 3Â ; True red ball trusses atop this dense hill of dark green leaves; consistent fall bloomer.

Coral Velvet (yakushimanun hybrid) EM, -5F, 2Â ; Coral pink flowers fade to light salmon; consistant fall and winter bloomer when temperatures mild; leaves green with fawn indumentum, silvery tomentum.

Elizabeth (R. forestii-repens & R. griersonianum) EM, 0F, 3Â ; Red trumpet shaped flowers on bush of dark green foliage; very tight grower, which also blooms in fall.

Melon Pink (Unknown) M, -5F, 3Â ; Delightful watermelon pink blooms in spring and often in fall; Neat medium green foliage with tan indumentum.

Songbird ( R. russatum & R. Blue Tit) EM, -5F, 3Â ; Glowing purplish-blue flowers cover this small leaved heavily branched semi-dwarf; some fall blooming also.

Yellow Hammer (R. sulfureum & R flavidum) E, -5F, 5Â ; tiny dark green leaves on upright grower; bright yellow small trumpet shaped flowers up and down the branches; blooms in fall too.

Among the azaleas there is a family of fall blooming azaleas called Encore azaleas.

Other fall blooming azaleas include:

Momo-no-haru - pure pink-lavender blooms; dwarf shrub

Sir Robert - variable light purple-pink blooms; large flowers, dwarf shrub

Arabesk - deep rose red

Watchet - pale pink; large flowered

Conversation Piece - white with purple-pink variations

Baton Rouge - pastel red-salmon-orange tones; a more refined and paler version of the popular Fashion, much more compact

Congo - striking purple

Jennifer - orange-red blooms

Thanks so much for that exhaustive reply, rhodyman, and for the paradigm shift into understanding that fall bloom is not necessarily a good thing for the plant or at least would cost blooms in spring. That makes perfect sense, and those sound like some lovely plants even without fall blooms. Gardengal, thanks for your voice of reason - I should add that I did like the plant independent of its fall blooms; they really only served to give me an additional reason, as if I needed one... and I have to admit that it is still a tempting attribute even knowing that it is not great for the plant, since it is happening so late in the season that there is truly NOTHING else going on (except some soggy chrysanthemums), and of course the conifers getting their day. Also I realize I made the assumption in my subject line that this would be something to be enjoyed/tolerated preferentially in the PNW, but upon reflection realize it must also happen, say in Pennsylvania, but just earlier in the year.