I have a plumeria that has blooms and buds but the leaves wont mature any ideas what could be wrong? Also the bark near the base where it enters the ground is partially deteriorated. I live in Costa Mesa California and other plumarius of a different variety are doing well in the same soil. the soil has been supplemented with cactus soil but naturally has clay based on the area... 3 miles from the ocean. about 4 hours of direct sunlight.

In my experience this spells trouble. You likely have either a badly developed root system, or it's the damage to the trunk. I would dig it up to see what is going on.

thanks... what will I be looking for...how can I prevent it in the future ie improve roots

An incomplete or possibly rotting root system is pretty clear. In order to have a healthy root system you need to make sure to have a very well draining soil; since you are dealing with a clay base you may need to dig deeper, and/or plant in a pot.
Once you have that baby out of the ground, take some pictures and show them here.

And bottom line - sometimes plants just don't do well. I had a mature, previously well performing plumeria tree just - up and die on me recently. Rotted clear to the ground. No earthly reason why this should have happened and all the ones alongside it are doing well.

thanks will do. I'm bumbed because it is one of the slower growing versions I have and has taken a while to grow.

I have a rainbow plumeria that I 'rescued' out of the ground a while back and the cambium layer is so damaged from sunburn low to the ground that the leaves do not mature . Hate to give up on it but the future for it looks mighty bleek.

here is what the root system looks like

this is after washing off the soil

Those roots look very compacted but I am willing to wager that your problem is absolutely that damaged cambium layer right above the soil line. The plant wasn't able to transport nutrients to the top.
You did the right thing by cutting it, and now you need to continue cutting (cleaning your clippers or knife between cuts) until you have clean white wood. Then let the cutting callous and start rooting.
Good luck!

With a decently healthy root system, will the plumeria not eventually grow a healthy stalk from the bottom up ? IOW's, from the root up in behind the now damaged cambium lower or is the plant, roots and all just toast ? I have tried to root cuttings off this once huge tree but they just appear so weak (very little white sap) and regardless of the rooting method, they just rot and die. Anybody have any advice ? tia .......

The cuttings are most likely weak because the plant has not been growing well. Once the cambium is damaged all the way around there is not enough nutrition going up the tree.
I doubt whether the plant will regrow from the roots....

It might be worth trying to graft a cutting on to a healthy plant.

Dutchlady1 said:The cuttings are most likely weak because the plant has not been growing well. Once the cambium is damaged all the way around there is not enough nutrition going up the tree.
I doubt whether the plant will regrow from the roots....

It might be worth trying to graft a cutting on to a healthy plant.

Thanks for the information. I did attempt two grafts to the very strong Celadine I have and both looked very good on completion but both ended up failing. I believe you are spot on about the plant just being to weak from the cambium layer damage. I'll continue to care for it to see if anything good comes up from below. Slim chance I'd say but it is hard to pull the plug.

I'm a few miles further from the ocean, but my poor plumerias have struggled too this year. The weather has really had a effect. More than our normal rain, a very long ,cool spring, with morning fog through much of summer has mine just getting into bloom mode, as the leaves are starting to drop due to shorter days They just didn't get the tropical sun they need to bloom well. They are healthy...but confused.