To answer previous question, I don't think any citrus where I live is very cold hardy after loosing almost all my trifoliate and Ichang hybrids this year. This Grapefruit and my satsumas and meiwa and Croxton survive winter here only because they are covered in 4 mil plastic and have space heaters controlled by thermo cubes inside their enclosures. The coldest temperature I know this Rio Red survived without space heater ( I forgot to plug it in) was a 19 degree night under it's plastic dome. It mostly defoliated that year, several years ago, and didn't bloom that spring. Another reason I'm surprised it's blooming so well now. The lowest temp I recorded this winter was 8 degrees F on 1/2/18, and it didn't get above freezing the first 7 days of January.