Those fragile N. apricots
If you've successfully grown Harrow and the couple of NJ release cold hardy apricots in Z6 or colder you are fortunate they are still alive.
I lost trees at several sites this season and haven't a clue what caused their demise. At two separate sites I lost Earlyblush, which is extremely disappointing as Bob Purvis suggested the NJ releases might be stronger than the Harrows.
One site would appear to be perfect- a short walk to the Hudson river with no hills between- just 40 miles north of the city. Well drained sandy soil- a Harlayne died there while a Harcot remains robust. The Harlayne replaced another tree that had died a few years back and had been vigorously growing there for 2 seasons.
Another site, where I lost both a Harlayne and an Early Blush, is on top of a hill and a mild 6B. A third site was neither on top of a hill or in a valley and also relatively mild where I lost another Early Blush.
None of these trees saw zero degree temps or periods of warming followed by hard frost in spring or sudden cold temps in winter. All of them are warmer than my own site where my early blush survived. None of the many trees in my nursery not far from the second site suffered any damage.
The soils ranged from sandy to clay and two of the 3 sites are very well drained and the one that isn't wasn't particularly wet going into winter.
I will continue to ponder any connecting threads but right now I'm completely baffled.