This is not a myth there are citrus that are -15F hardy but it’s a short list. Yuzu is reportedly hardy to 10F but it depends on your tree. Some survive -15F
Poncirus trifoliata can survive -15F . Some are hardier than that.
Poncirus Plus
“A selection of Poncirus Trifoliata that lacks or greatly reduces the characteristic resin/bitter compounds of a typical Poncirus Trifoliata.
Origin
Europe
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Submitted by
Brady Mitchell •@cascadiaadmin
Colwood, British Columbia, Canada
Submitted on: December 30, 2025
Last Edited by
Brady Mitchell •@cascadiaadmin
Last edited on: February 21, 2026”
“ Conestoga 010 are F2 hybrids between the Ruby blood orange and trifoliate orange selected by citrus breeder Mel Martin. Both fruit strongly resemble the trifoliate orange; 010 has less resin and 026 has more orange flavor.
These plants are recommended for growing outdoors in plant hardiness zones 6-10.”
Conestoga 026 Citrange are F2 hybrids between the Ruby blood orange and trifoliate orange selected by citrus breeder Mel Martin.