Oh no, it does sounds like rot, I think you are overwatering it. Plumerias tend to go dormant in the winter, at this time they will lose some or all of their leaves, water sparingly or none at all. You should get a water meter and test the soil often, if it shows red then give it some water if it remains in the green then don't water--but this is only for during the growing season not when they are dormant. What I think you should do now is get a pin or needle and poke the trunk of the plumeria, if white latex comes out then its still alive, if nothing comes out then I'm sorry to tell you that it has rotted, and the next step you should do is cut off the rotted part until you see white clean wood and try to root it as a cutting from there. I'm by no mean an expert, I'm a newbie myself, I just started growing them about 4 months ago, this is just my honest opinion......
So sorry about your plant and the best of luck to you..

Nikki T

Nikki-

I just pricked it, from base to top, in about 1in incriminates. It oozed white at every place i stuck it.

Thats great news!! It might be coming out of dormancy, the top should be shiny and green, how about the soil, do you use a well draining soil? I use cactus mix for mines, and don't repot until you see roots coming out of the pot. Too big of a pot for so little roots and too much cold wet dirt around the roots can stimulate root rot.
I have a few cuttings that are rooted but the trunks are wrinkly, what they need is light. I would place them next to a sunny window where they get plenty of sun light. The trunks harden in a couple of days. Good luck!!!

Nikki T

the top is indeed shiny and green. I put in in the south facing window, behind a sheer curtain. I hope it comes back! I will need to repot it. When I repotted it last week, i put it in a large pot with regular soil. i will put it in a smaller pot woth cactus mix, i think i still have some lying around. In fact, I am going to look right now! I will update you in a few days. thanks!

Oops, I have the same problem !!! It was doing fine until I re-pot it in a larger container. I don't know where I went wrong, I used cactus soil mix. Tonight I took a closer look at the branches, the smaller one was rotted, I had to cut it all out. I'll have to follow your suggestions, nikkit, hopefully I can salvage it, the green part is small, maybe I should root it in a plastic cup. I'll keep you posted.
Annamaria

I don't know.... My first winter I had my plumeria I underwatered.... the plumeria stem/trunk became soft and squishy because I was not watering it enough and it was not retaining enough water.

Easy test for your plumeria: give it a good soaking watering. give it 12 hours... if the trunk/stem plumps up and gets firm it simply needed more water. if it does not plump back up and get firm you probably have rot somewhere.