Plants rotting

Hi everyone , i have in my garden 6 cordylines of 3 different varieties ,3 in ground and 3 in tubs ,also 2 Phoenix date palms in tubs . All are established ,been there 10 years plus , recently the growing tips have gone mushy and rotted and fallen out ,followed by leaves wilting and dropping . Can not understand this ?? Any thoughts please

 

@ashley1234
As shiney says the cold weather in December and then later in the winter has wreaked havoc with many slightly borderline plants.
Some plants that came through the bad winters around 2010, the Beast from the East in 2018 actually succumbed to the pre Christmas cold snap last winter.
Possibly because there was a mild damp autumn and plants kept growing later and so hadn't shut down completely when the cold weather came.
See here RIP cordylines
and Cordyline Calamity
It is possible that the cordylines in the ground might come back, remove the rotten and dying bits and then wait as it could be well into the summer before there is any growth from the base. If any become loose in the ground then the roots have gone, so dispose of.

 

i have sawn off at a angle and duck taped over the three cordys that are in the ground , do think they may shoot again below the cuts ?

 

Cordylines will more likely shoot from below ground.
Just knick the bark with a knife, if it's brown underneath the whole stem is dead.

 

I will also wait with fingers crossed ,thanks

 

Ok ,will try that ,thanks

 

I have just got back from RHS Rosemoor and noticed that some of the hebe had been hammered, Some had a green half and a brown half, in many cases the brown halves were showing small green leaves at the tips.

 

I have lost quite a few plants and one tree due to the December freeze. Heucheras and a Lavender were least expected. I can't see any signs of growth in five of my Salvias.

 

I suspect I have a lost Salvia confertifolia and S involucrata, several plants of each, normally I have cuttings of each, but this year the drought meant that there wasn't much growth until later and then they didn't root.
Won't know for sure until end of May.

 

One of my two Colquhounias is now deceased; curiously the more sheltered one is deceased' I suspect this was more the drought than the cold.