What happened to the tree and made it loose all leaves, frost? Ants around citrus usually means they are cultivating aphids.

If you do not control the ants, you WILL have aphids. It is not the ants themselves that do damage; it is the critters they bring to work for them.

Dnedd1... I bought my house 4 years ago and only recently discovered that the tree was an orange tree. I thought the tree was dead for sure, but got some excellent advice on this forum and it looks like it's coming back to life! I just worry about the black discoloration on some of the branches. It has lichens growing on the trunk, but I imagine that's because the poor thing hasn't grown in 4 years!

John merr, thanks! I will get rid of the ants.

Yes, it does look like it pulled through my mature Satsuma's that lost their leaves in the hard frost are also leafing out now and look to be a few days ahead of yours in leaf growth, but I am 40 miles south of you so that makes some sense.

I wonder if there is a void space underground that the ants are using.

Honestly, it doesn't take much to make them happy.

Aphids are not always sure to follow, but it is good to keep an eye out.

So glad to see those new leaves coming on your orange! My potted kumquats are starting to put on new growth, too :)