Due to massive growth in the density of housing in my part of the metro area, the deer have been squeezed out and their density has skyrocketed. I have a red dogwood which was at least 25 years old. But despite my best efforts to protect it from deer rubbing (you can see the type of trunk wrap I use on all my trees in the last photo), it has been repeatedly injured over the years and I was distressed to find its trunk completely broken in half last fall. But this spring, I was surprised to find lots of flowers on branches which are now lying on the ground. I'm astonished, as there is just a tiny remaining connection between the bulk of the tree and the base. Surely it's last hurrah! Sometimes nature's resiliance amazes me.
As well as the white flowered ones do by layering... I'd try tossing some mulch or soil on top of branch where in contact with the soil... You should be able to get a new tree.
I'd be thinking about some kind of improved deer barrier.
I find that fencing off the entire yard is far more effective than trying to protect individual specimens.
I didn't know that you could layer dogwoods. I think I'll try it. Thanks for the suggestion, Stone. As for fencing, unfortunately can't be higher than 4ft in my city. Not worth it. I agree protecting individual young trees is nearly impossible, so I've quit planting any more trees. I'm glad I planted bunches of them 20+ years ago when the deer weren't so bad.
I've given fencing serious thought over many years, but it would be difficult (and expensive) to do it properly. I have 2 acre lot which is wooded and sloped and which has a small stream running through the middle (hence the high number of deer!). I was told I could petition the city council with a fencing proposal but it would require tons of paperwork as well as a formal survey of my property. Out of pure desperation, a few years ago I installed 400 yards of 7ft tall heavy-duty polypropylene deer fencing around a large portion of my yard a few years ago (I figured the polypropylene fence wouldn't be visible to anyone driving by). But my staking efforts were comically amateurish and the deer have successfully breeched the barrier in many places - the remnants won't keep out a rabbit. So I give up...
I know Tractor supply has strong steal fencing 5' high that you can drive in posts around the tree and create a barrier around it. That shouldn't create a fencing issue in your town.