Here's some info from Floridata.com: https://floridata.com/plant/31 States that flouride in the water can cause leaves to brown. Are you watering from overhead or at the base of plants?

Ciedyline is not an annual. I successfully overwintered mine for several years. After it “trunked,” I tried following the advice of dear Campanula, to score the trunk to stimulate growth lower down. It died soon after.

That sounds beautiful! I was out in Vancouver last fall and was amazed at the green ones that were everywhere. I knew they grew there but to ssee some of those tres in person I was so happy. So I just did some checking back in old photos. I have had it late winter for the past 3 years. It does out grow it and not having to treat it. I always thought it was from the cooler temps in Jan, now I know! As far as I have noticed nothing around it gets infected.

if dead.. things rot .. and eventually it can be easily pulled out.. whats your hurry No "hurry", per se, other than the aesthetics of it this or next year. I liked the look of the mandevilla with it, but I don't have any this year so I probably won't do that again until next year. I was also concerned that the roots of the mandevilla could be wrapped around the roots of the cordyline, and its rotting could lead to killing the other. If that's not an issue, though, then I'll just cut the old stalk down and let it do its thing :-)