Hello Zac, where are you and what kind of tree is it?

Typically there is not much if anything to do. A potentially big pin oak next to my house I might remove. A redbud which just is unlikely to cause injury or damage I'd let go.

Thanks for the feedback. This is a ruby red horse chestnut and I'm in Pittsburgh.

if that is SW facing.. sunscald .... and maybe in winter ...

nothing you can do about it ... it will either heal itself.. or it wont.. btw .. there is significant healing already happening.. meaning the injury was futrther back in time... rather than when you first noticed it ... this stuff doesnt happen all this fast .. rather it happens in tree time ....

my mcNairs ... got that a year or two after planting.. 10 years ago ... its about 4 inch caliper.. and completely rotted inside ... and still standing there ...frankly.. its defying physics for the last few years ... lol ...

whats the yellow stuff below the very low leaves ... weedwhip damage.. or lichens???

i would also check to make sure it at a proper planting depth ... the root flare should be at the surface ... this can cause this type of problem.. if you have a few inches of trunk underground ... pull back the soil and find out ... let us know

https://duckduckgo.com/?q=root+flare&t=ffcm&iax=images&ia=images

ken

Sometimes a severe bend from a wind gust can cause such a split. Should eventually grow over the split.

Is the split obvious from the opposite side, as well?

I agree with Kenn, this is sun scald that occurred in Winter.

I had this happen two years ago on my favorite Crape Myrtle. I ended up cutting down the trunk and replacing it only to have the original damaged tree recuperate from the roots and forming a new tree.

Areas that get lots of Winter sun and Winters that feature cold alternating with heat encourage this kind of damage and two February of 2017 was record warm in the Northeast.

Thanks for all the feedback. Ken- it is facing SW so all the ideas on sunscald are probably accurate. The yellow marks are lichens (not sure if that's good/bad) and I feel like they're at a proper plant depth. I recently mulched and its a little thick...

lichens are of no concern ... and are very cool to look at ..... ken

https://duckduckgo.com/?q=lichens&t=ffcm&iax=images&ia=images

btw.. in the cold of winter ... the sun will be at its warmest in the afternoon ... and the bark on the sw side of the tree.. can go in and out of freeze/dormancy .... and that is what causes the tissue under the bark to die ... and then.. in tree time.. a year or two later.. the would opens .. and presto.. you are wondering what happened ... and very rarely think back to things that might have happened the year of planting... or the out of the ordinary winter ....

ken