Yes they are, some just keep flowering and never fruit, I have one from Abiu I ate in Kona, is 15 Years old, 5 meters high has been flowering for over 10 years never set any fruit, is isolated, I plant another young tree over couple years ago 40 yards from the old one, the young at the second flowering and only over two meters high set two fruits, I thought this would help the older one with cross pollination but didn't happen, now the young is in full flower again, I also have small one year old, E4 seedlings flowering for first time at less than a meter high, from my unproductive old Abiu tree I never noticed those flowers really open up, always stayed close until they fall, not know if that is common...
