I grew a few Asimina triloba from seed and they did great after spending 4 months in the fridge in some damp peat moss. I sprouted a few wild ones and some improved varieties from Cliff England. The wild ones I will be grafting over this coming spring with named cultivars. I never tried growing Asimina obovata, Asimina incana, Asimina reticulata, Asimina longifolia, Asimina pygmaea, or Asimina tetramera. Do you know what kind you are growing?