Hydrangea are not trees botanically but sub shrub

they have soft-ish wood which ages badly and

-good news-

have the ability to regrow from dormant buds and shoots from the base

so it should be ok to cut above all sprouting eyes.

to trim a sub shrub as a tiny standard tree goes against their nature, they tend to regrow and re-juvenate frome the base.

so I personally would regrow it as shrub and then just keep pruning it in intervealls, good luck,

Lin

edited to ad: one way to properly prune Hydrangea paniculata ist to cut back most of the old growth in spring

Not a subshrub but a shrub by growth pattern. To regrow as a ”tree” form I would prune it back to near where it has started budding and the let it grow as it will for this year to recover, though I would remove any sprouts farther down, on the ”trunk” part as soon as they appear. Then next year if it needs shaping, start pruning for shape.

IME the old wood does not age badly. I have branches on some of my panicled hydrangeas that have been there for more than 10 years.

I would prune it back to live buds. I would also replace it with a new one until this one rejuvenuates, presuming this is a specimen tree -- but that's just me. It should eventually grow just fine but may take a while to get back to a nice shape as a standard.

BTW: I don't think that's rabbit damage, rabbits can't reach that high. More likely it is deer damage -- they rub their antlers against bark to remove their felt.

I protect the trunks of young trees come about August or so. I've also wrapped lower limbs of certain trees in tree protector stuff -- yes it's ugly but it works against this type of damage and is just to tide the tree over until the felt rubbing season is passed (I remove it in spring).

Thanks so much for the help everyone, very helpful. I'm going to give it a good pruning today.

mxk3z5b_MI, we got an insane amount of snow this year and allowed the rabbits to access it that way. We don't have any deer in my neighborhood.