In the spring, I purchased 2 rhodo's from a farmers market, I suspect the plants came from Tennesee and I live and planted them in Michigan. I noticed when I bought them, they had ashy black buds that were dried out. The looked sickly through the spring and into summer until i picked off the buds Then the plants took off like crazy. Now in September, they are starting to grow buds again. Should I remove them before winter? What does this mean
You are likely to have problems with hardiness in Michigan. Rhodos , depending on the species, may be hardy to Zone 5. In the Pacific North west, where rhodos grow sometimes to tree proportions, blackened buds are sometimes from winterkill in a year of severe weather. Buds forming now will give next years blooms and new growth. Good luck with overwintering your plant!
The symptoms also resemble those of Rhododendron bud blast caused by the fungus Pycnostysanus azaleae. See: http://www.rhs.org.uk/advice/profiles0500/rhodo.asp
It is the normal development cycle for Rhododendrons to form buds in fall for the following spring's bloom. If these new buds look and feel OK, I would suggest to leave everything alone until such time that further problems become apparent.
Many rhododendrums are plenty hardy (some are not) and can be grown in michigan with no problems if protected from the wind and winter sun. Since the ground freezes solid, wind sucks all the moisture out of the leaves and you'll end up with wind burn. The sun can burn the leaves too but would be concerned with bud blast cause from buds freezing/thawing from the winter sun. The key to growing in michigan is protection. My parents have had Rhodos with +5 to +10 hardness growing there for over 30 years (thats many sub zero days) but they are very well protected by hardier rhodys and evergreen wind breaks.