some of the "Live Oaks" in N TX developed frost cracks after last winters cold. These cracks are at the base of the tree so if there was not any mechanical damage at some point I would say they are frost cracks.

Tengage, that doesn't look good. But......there is nothing you can do about it. Primarily, the tree was planted too deep and now there appears to be some kind of bark disease or decay of some kind. I see another split forming.

But bottom line, it's too late to fix. May as well just see how it does..

+oM

Here is the relevant picture:
{{gwi:327162}}

If I was going to try to keep that tree, I would at least remove all but a very thin layer of mulch (or all of it) up against the trunk. The extra mulch is holding moisture up against the damaged trunk and encouraging rot. If the tree is planted too deeply (we can't tell from those pictures), that could be part of the cause of what's happened (or at least exacerbated the issue). Given the location and nature of the damage (and especially if the damage continues all the way underground), I'd probably prune the tree at ground level, apply glyphosate to the freshly cut stump, and start over the right way.

if it were planted too deep ... i doubt it would have grown from a twig to that in 6 seasons

i bet OP did it when they added the brick

pull back the mulch and soil ... and snap us a new pick

as to the damage .. not all that uncommon ...

were you in heavy drought this summer??

ken

You can see where crack has grown back. I'm with Ken, I think the bed was added after the tree was planted. This is pretty common in those types of landscapes in north Texas.

I don't see any sign at all of where a crack has grown back (even with the large version of the picture). Do I need new contacts or a new monitor?

Still, and as I said above, we can't tell how deeply the tree is planted with the pictures provided. New pictures, with the mulch (and possible some soil - can't tell that either) pulled back until signs of root flare are evident, will be needed for determination.

Brandon, thanks for adding the picture. When I bought the house, there was a mound of mulch on top of the sod, on top of the burlap bag around the root ball. I did the stone border about a year after we moved in. I think I'm at about a couple of inches above where the burlap bag was and I think the dirt is a bit lower now than where the original mound was. I'll compare with some old pictures and I'll dig down a bit tomorrow and take some new pictures. We did have a bad rain deficit over the summer and the tree probably didn't get enough water. I can't remember when the split started but I got a bunch of new growth last year, more than normal.
Besides lowering the dirt level, is there anything I can do to help keep the split from getting worse or rotting? I normally use pruning sealer when I prune the tree and thought maybe it might help this crack. I'll update tomorrow. Thanks everyone.

"...there was a mound of mulch on top of the sod, on top of the burlap bag around the root ball."

Well, that's enough info for us to know for sure that whoever planted the tree didn't know what they were doing. You need to dig down to that burlap and see what's still left. If it's still present, remove as much of it as you can without significant root disturbance. Unfortunately, it's too late to get the vast majority of it, but removing what's on top may be slightly helpful with moisture control (reduce possible wicking effects). Look for signs of the rootflare. If you're not sure what you are looking at when you do the work, post pictures here. If/when the rootflare is evident, recover the area with a light layer of mulch (very light to none up against the trunk) to reduce evaporation (as well as for aesthetic benefit).

"I can't remember when the split started..."

The damage may have been done long before you noticed anything. It is quite possible that only close inspection by someone that knew exactly what they were looking for would have noticed anything wrong until quite some time after the underlying damage occurred.

"I normally use pruning sealer when I prune the tree and thought maybe it might help this crack."

Do your trees a big favor and throw that junk in the trash (unless you have a specific and unusual circumstance that warrants it's use). Pruning sealer (at least for the most part) is contraindicated for use on woody plants.

I'll save the pruning sealer, the can says I can use it to repair cracks in asphalt and also to coat the "undercarriage" of my mower, yeah I guess it doesn't really sound like the stuff that belongs on a tree.

Here's an old picture of the tree. I looks more like a weed.

I'll find out how far down the roots are tomorrow.

{{gwi:327164}}

The outer bark split, it's dead anyway but the line you see is last seasons growth which has grown back.