PT-2A4 is a primocane-fruiting (fall bearing) black raspberry, the latest product of a breeding program that uses genetics derived from a chance primocane-fruiting wild seedling found in the Hudson Valley, New York in 1986.

 PT-2A4 is a successor selection to the Explorer black raspberry, which, unfortunately, was found to require an outside pollinator. The background genetics of PT-2A4 are similar to Explorer, except that the original cross was in the reverse direction, and there is an extra generation in a couple of places in the pedigree of PT-2A4.

PT-2A4 was selected for good production of large primocane fruit and large floricane fruit, and was proven to be self-fruitful. Compared to Explorer, PT-2A4 has larger fruit, higher druplet count, and smaller seeds.  Occasionally, the shape of PT-2A4 berries can tend slightly toward conical to accommodate the high number of druplets. Like Explorer, the primocane-fruiting trait is very reliable. Berries start ripening in late August or early September. Sadly, the reduced thorniness seen on Explorer is not present in PT-2A4. 

PT-2A4 is not yet named; it is being identified by its selection number. (Naming suggestions would be welcome.)  PT-2A4 is being distributed for very limited initial trials under a strict non-distribution agreement. PT-2A4 plants are not yet available for purchase. 

This pruning guide for primocane-fruiting black raspberries might be useful for testers. The training differs in a few key respects from the pruning guides for standard floricane-only black raspberries.

Thanks go to my local Cooperative Extension agent for the photo below called “Raspberry Trifecta” taken in September 2008. The black raspberries are a mix of PT-2A4 and Explorer, red raspberries are a mix of Autumn Britten and  Polana, and the yellow raspberries are Fall Gold.