The large rhododendrons of the NC mountains are the species rhododendron maximum. This species would likely be hardy enough for your present area, but it would take many, many years - if ever - for any to approach the size they achieve under the ideal growing conditions they enjoy in the southern mountains. Most rhododendrons transplant with relative ease, but large ones would be extremely heavy and very expensive if you could find some place to purchase them.

I have a number of mature ones on undeveloped land in NC and am thinking of moving one or two. Do you have any tips for making sure they survive and thrive?

The larger the rhododendron, the more difficult the move. If you're contemplating transplanting even a 5 or 6 foot specimen, you will have to dig out a very large rootball to increase survival odds. Even a wide, shallow root mass such as rhododendrons have would weigh in the hundreds of pounds and cannot be allowed to dry out during transport or after planting. Honestly, the most likely result of trying to move mature rhododendrons from NC to NY is a great deal of work followed by the death or at least severe set back of the plants. You'd be far better off planting smaller rhododendrons in the 3 to 5 gallon range. I wouldn't do this either until a soil test indicates suitable conditions for rhododendrons. If you see few or no rhododendrons growing in the general area, that's usually a pretty reliable indicator that conditions are not favorable even though climates seem superficially alike. Your extension service or state agriculture department can offer valuable advice in this area..

Though I broadly agree with mainegrower, it's worth pointing out that rhodies in more benign climates are actually considered rather easy to move, because of their compact, fibrous root systems. Years ago Greer Gardens, in Oregon, would dig up huge 8' tall rhododendron specimens in full bloom, place them in a Willamette Valley shopping mall for a week, during some kind of local gardening festival/event, and then put them back in the garden...none the worse for wear.

BUT those were plants under cultivation going back into the same spot, and not being moved very far; I agree you should abandon your idea to move wild, deeply rooted shrubs from NC to NY.

Too bad you didn't have this request 8 years ago or so. When Hank Schannen of Rarefind died in 2009, the nursery had to sell many large specimens to keep their accounts good and make payroll. That being said, you should check with any large east coast rhododendron nurseries. Sometimes they have large ones they wouldn't mind parting with.

Thanks for this valuable advice. How would you go about finding large rhododendron nurseries in my area?

You should also put the word out locally that you're looking and willing to dig them out. In my area further downstate, huge rhodos are everywhere and people often take them out when redoing landscaping because they tend to get too large and lanky for typical suburban landscapes without diligent pruning.

Go to Adam's in Kingston. They are the best nursery around. Also, Woodstock is really the northernmost limit for rhododendrons (zone 5) and will require a warm exposure. NC is much further south. PJM rhodies do very well in your area and can grow to those heights on the shady side of the house.