this one was grown from a seed of a Citrus ichangensis x Poncirus trifoliata hybrid

this one was grown from a seed of a Citrus ichangensis x kumquat hybrid, it's grown to be quite big now, in front of it in the smaller two cups are Citrus ichangensis itself, and a kumquat that I grew from seed

Both these hybrids should be able to grow outside here, but I'm keeping them inside under special grow conditions until they get a little bigger.

The ichangensis x trifoliata should be able to survive zone 7, while the ichangensis x kumquat should be able to survive the colder parts of zone 8 further north.

on the left is a seedling grown from a Changsha mandarin x trifoliata hybrid, and on the right is a seedling that was grown from a Citrus taiwanica x trifoliata hybrid.

Both of these should be able to survive zone 7.

Both Changsha mandarin and Citrus taiwanica are quite hardy by themselves, so you can imagine how much more hardy a trifoliata hybrid of them would be.

I talked to Nat Bradford (yes, the descendant of the creator of the legendary watermelon variety that bears his name) and he told me he grew Citrus taiwanica in Seneca, SC, on the border between zone 8a/7b and the plant seemed to be very hardy, it didn't lose its leaves over the winter and it had many fruits. He said he went back several years later to his old property and the tree was still there. This was after the devastating 2017-2018 winter freeze. (He actually said it did better than an ichangensis that was planted next to it)