I chose alias "Citradia" on forum because from my research, citradia is supposed to be the hardiest trifoliate hybrid, hardy to zone 7. I'm on border of 6b/7a, and originally hoped to find a citrus hybrid better than poncyrus to grow unprotected outside. Ironically, my citradia that I planted on south side of house died back from 4 feet tall to two inches above soil line this past winter. It was protected with 30 gallon garbage can of water and varying forms of expedient coverings from frost cloths to 4 mil plastic sock stretched over wire dome-shaped cage. I had three Dunstan citrumelo treated in similar fashion, and two out of three died completely, with one only defoliating but loosing no wood. The citrumelo seedlings were 3 ft tall and all came from same fruit. I had two nights this past winter reaching zero degrees F.