OK, let me explain the problem , I have a beautiful Linden tree in my property, 60 foot high, may be more than that and the unit is forked 4 or 5 feet from the ground creating between the two branches an hole about 1 food deep.
The skin is perfect even inside the hole, however, my worries is that, I am in Canada and here the winter is very cold, the water freezes and I am afraid that one of these years the rain penetrating between the two branches and then freezing will spilt the tree and I hate to call the house insurance for repair.
My question is: does anyone know if there is any compound on the market to pore inside the hole so that will prevent the rain to lick through and expand as ice

I remember, when I was a kid, my father mixed up some concrete or mortar and poured it into the hole. Then he painted it to seal it.The tree did good as far as I remember. If he cut off a branch he would use paint again to stop the tree from bleeding out sap.
I don't know if this is the best way to take care of this, but that is what he did 50 years ago. It was a Maple tree.
Might want to ask a tree surgeon or a nursery before pouring concrete. They might have something better today. Bob

Thanks Dogbone, I shall consider your suggestion too

Cement is the wrong way to go as it will speed up rot. You need to contact a company that works on trees with damage and do this soon or it will split open. We have been working on trees over 40 years now in FL.

Thanks John blue, I will contact the proper company ASAP.
what I was hoping to find some "gluy"stuff that penetrates within all parts of the cavity and solidify with time and that preventy the water to sip under.