I have a coworker that doesn't know a whole lot about citrus that I share an occasional fruit with. a few years back he told me he had a navel orange and seeded grapefruit planted. this year he brought me one of his "navel oranges" that finally fruited. he knows it obviously isn't a navel but doesn't know what it is. the second I saw the leaves and numerous thorns I knew it was rootstock, I just don't know which one. figured you guys would have a better idea.

I forgot to add hes also worried about it losing its leaves on one side, though that seems like a moot point to me. he says he may use the fruit to cook the peel and make something with it, not sure what that would be. hes not from America so he may know some fancy things to do with fruit, though I cant imagine a trifoliate rootstock working for it...


im interested in whichever variety it is, would it be compatible to at least try to graft any of my trees onto seedlings for my own entertainment. I suppose id like something that could fruit one day, but I just want to know that success is an option, which would be the best of my varieties???

The leaf is clearly trifoliate, but the fruits are too big for any citrange - so that leaves us with citrumelo. Often used as a rootstock, but the exact variety is almost impossible to decide. Probably the Swingle citrumelo is most likely. What does it taste like? Probably not very nice!
Yes, you can use the seeds to grow rootstocks for grafting.
If the leafless branches look to be dead (try scratching the bark - green underneath is alive), then they should be cut back to where there are live branches. Be aware that in cold conditions, trifoliate hybrids can have a tendency to lose leaves, but it doesn't mean they are dead.

yea after looking through the forums I tend to agree that it is swingle also. the best I could do is touch it to my tongue, not very nice at all lol.

the branches didn't seem dead to me, but they had spots that were splitting and healed up already, almost like something chewed the bark off of it. im not even sure what would do that kind of damage or if its related to the leave drop.

I vote for swingle

Yep, swingle.