Question
Hello,
I have a 200-250 yr old beautiful and tall oak tree on my land with two main limbs rising up from the trunk and a third smaller one.  A split is forming in the middle of the 'saddle' at the very top of the trunk between one of the main branches which is on one side and the other main branch and the smaller one on the other side.  As it is right at the top, it is exposed to rain.  At the moment there is a hole about 6inches deep.  I've read the article where you advise to not fill it, so what should I do?
Thank you so much for your advice.
Manfred

Answer
Leave it alone. I would imagine that an oak this old would have some hollow space in the center of the wood. This is normal for this old of a tree. IF a decay fungus does get into the wound (crack) it will not effect the health of the tree. Do nothing anything that is done would cause more damage then letting it go. As long as the foliage is green and healthy looking the tree is OK.