Hole in windmill palm trunk

[squiggly001]

I transplanted this windmill palm about 4 months ago and it has a big hole in the trunk. The owner said it has been like that for many years and he doesn’t know what caused it, the tree still seems perfectly healthy but I’m concerned it will cause issues from water getting in and sitting. I’m thinking of spraying the inside of the hole with a coat of tree sealant then filling the cavity with spray foam and covering the hole with some extra trunk fiber I have , what do you guys think? 

[Joe NC]

All of my windmill palms have the "root initiation zone" extending about a foot or more up the trunk from the soil line.  It seems to creep further up the trunk each year, and results in a flare at the base.

I live in NC, I have rather heavy clay soil and it is pretty wet here.  So the roots that form up the trunk usually successfully make their way into the soil and grow. 

I had one tall windmill that was kind of wobbly after a hurricane, so I took advantage of this rooting ability and piled up a bunch of mulch around the base to encourage new roots to form up the trunk.

It worked, new roots grew from the higher root initiation zone and this plant is well anchored.

I wonder if you could use this "hack" and encourage roots to grow around the base and hole.  Perhaps even above the hole?  This would give the palm a stronger base and maybe even cover the hole?   

[Allen]

Probably cover the inside of the hole and around it and see if new roots form from the root zone as said above.  But the palm may be in jeopardy long term.  It's a experiment

[Allen]

3 hours ago, Allen said:

Probably cover the inside of the hole and around it and see if new roots form from the root zone as said above.  But the palm may be in jeopardy long term.  It's a experiment

I mean fill inside of hole and mound around with dirt.  My post wasn’t clear

[squiggly001]

12 minutes ago, Allen said:

I mean fill inside of hole and mound around with dirt.  My post wasn’t clear

I’m afraid if dirt gets in the hole it will rot the inside of the trunk, the tree is still strong and stable but I agree long term when it gets bigger and heavier it may be a problem. Also wouldn’t mounding the dirt up the trunk make the lower roots too deep underground to thrive? I always plant them at the same depth they were growing in the field 

[Allen]

2 minutes ago, squiggly001 said:

I’m afraid if dirt gets in the hole it will rot the inside of the trunk, the tree is still strong and stable but I agree long term when it gets bigger and heavier it may be a problem. Also wouldn’t mounding the dirt up the trunk make the lower roots too deep underground to thrive? I always plant them at the same depth they were growing in the field 

Please google 'root initiation zone' as a earlier poster said.  Your root initiation zone appears to be above the hole.  This is a odd problem and honestly that's a large hole.  Anyway that is what I would do is put dirt all around and hope it responds and grows new roots in that area.