I know that several were found a number of years ago in various gardens in the Midwest and those were the first introduced. I imagine that breeders have been using those and other more recently discovered plants with that tendency to bloom on new wood in their breeding efforts. IME many new plants start with a chance discovery of a genetic variant, either of a whole plant or a branch sport, that is then used in crossbreeding to bring in a range of other genetic variation along with whatever the new discovery was. So perhaps variegated foliage was discovered, and that might be crossbred with a plant with prolific bloom to get a plant with both variegated leaves and prolific bloom from the offspring.

The original development of new wood blooming macrophyllas was undertaken as a breeding program with various cultivars that were known to exhibit a degree of remontance. These included Nikko Blue, Dooley, Penny Mac, Souvenir du Pdt. Paul Doumer and Generale Vicomtesse de Vibraye.

Dirr presents a full discussion of this process in his publication, Hydrangeas for American Gardens. He is a recognized hydrangea authority that is considered the founder or leading figure in the development of the reblooming or new wood blooming bigleaf hydrangeas.

Very interesting. Thanks for the information.

It also helps if Mother Nature does some of the work for you! Penny Mac was a very useful specimen. Kind of like finding one of those Annabelles that bloom pink instead of white. I think they found one(s) of those Annas off the Gulf States and then NCSU tweaked it to release it as Invincibelle Spirit.

'Dirr presents a full discussion of this process in his publication, Hydrangeas for American Gardens.' Dirr's book is a must have for the serious hydrangea grower. I ordered a used - but almost perfect - copy from Amazon and use it constantly. It is a small book packed with charts, photos and very helpful information. A new book is expensive - around $224.00 and up, but used copies are around $34.00.

Another favorite book of mine is Hydrangeas, A Gardeners' Guide,by Toni Lawson-Hall and Brian Rothera, Timber Press, 1996. I found this book at the E. Miller Botanical Library, Seattle, WA. at their annual book sale. Just checked Amazon and used copies are available from $2.50 up. Quite a bargain.