Sitting water will eventually hurt it. Thing to try to guess is if the tree is going to close off the area or otherwise widen and change the shape before it becomes and issue.

Is the bottom of this area mushy yet?

My white ash get this same issue. When cut and sliced you can see the stain from the water down six or eight feet in some cases down their trunks.

What to do? Who knows. Horticultural medical care is in its infancy. Dogwoods can be picky fellas anyways.

Yours is great looking btw. Nice view.

Thanks!

Once I drain it, I will check for any rot, etc.

I live in west central Oklahoma and cut down a Dogwood because it had long thorns that punctured my mower tire. Be careful when mowing so you will not suffer the same fate. I also have Bois D'Arc, Autumn Olive and Black Locust with thorns, but they are not as long as the Dogwood's. Photo of Bois D'Arc tree is attached.

Graydog, do you have pictures of the leaves on that dogwood with thorns?

I have cornus florida, cornus controvera and cornus whatever the red twigs are and they do not have thorns.

I really doubt there is anything you can do about this that would be beneficial to the tree. Drilling holes, inserting a "straw", sawing channels, filling the void with foam, etc are much more likely to harm the tree than leaving it as-is.

Graydog.....mistaken identity on the thorny dogwood.

graydog, what you show is Osage orange, not dogwood.

Edit: OK, seems you know that is OO. But no dogwood has thorns.Some Bradford pears have simple, dogwood-like leaves and nasty thorns, so that might be it.

This post was edited by beng on Sun, Jul 14, 13 at 11:26