palm trees (type I think?)

I've never tried such a thing so as to wether it would be OK or not I wouldn't like to say.
Are you saying that the neighbors garden is that much higher than yours?
If so, is there no way you can retain the soil at the boundary?
Pesumably you will have to at some point, even if you build up the soil in your garden.

 

I wouldn't worry about burying 50cm of the trunk, this is far more preferable to lifting and replanting as Cordylines do not like to be moved and may not survive. Plastic piping filled with stone should be fine.

 

Cheers, Havent got much choice but to have a go, ground really does need to be raised and I cant afford to try moving them.

 

Its not a good idea to bury tree stems/trunks of any kind.
Thats why they always say "plant at the same depth that they were growing in the pot."
Cant see how its been at this level all this time and now it suddenly needs to change dramatically.

 

Thanks pete, guessing you got more Idea than the rest of us, but havent got much choice but to do something fence is buckling quite badly. if I put a wide pipe around them and left a 100mm gap around trunk then put a grill at ground level would that be Ok?

 

Not sure what you mean about the grill bit.
I still am having a problem understanding why you cant retain the soil at the fence line, surely you will have to retain it at some point?

 

I am with Pete on this one as I am finding it impossible to judge the situation in the absence of a picture
Now, admittedly, I get more dense as I age

 

On thinking about it, I have an idea what you mean about the grille, pesumably laid over the hole and around the stem, to stop bits and pieces collecting in the pipe.
Its an idea but not something I would like to do, how the trees would react I wouldn't like to guess. They may grow a new root system higher up the stem, on the other hand they may rot.
My money is on the last one, but who knows?

 

Wouldn't the pipe just fill with water?

 

No open to ground below so would soak away, would use filter pipe (holes in it) and maybe fill with stone?

Dont really know if it is a good Idea or not.