Probably the main roots are all caught up in a wad due to careless container culture at a production facility - the irrigation work may have included cutting through part of the minority of roots that escaped the knot and grew out, to partially anchor the tree. And now part of that partial anchorage is gone, allowing the tree to move on the fulcrum-like ball of deformed roots.

Dig around the crown to see if this might be the case. If there is a turnip of circling, mature woody roots frozen into position you may have to give up on the specimen.

This post was edited by bboy on Sat, Mar 22, 14 at 23:00

Thank you so much for your response and suggestion, bboy. I will do this tomorrow, but could you please tell me how far out from the tree and how far down I should dig so that I won't damage any roots that may be good roots? Also, if by any stroke of luck, I don't see the situation you've described, do you know of a way that I could try to firm the tree up in the ground, or is it still probably a hopeless case? I measured, and the main trunk of this tree is 10 inches in case that information might be helpful, and it's also taller than I originally posted; probably more like 10 to 12 feet. Thanks again!

Dig near the base of the trunk, maybe using a tool at first and then your hands when gouging might start to become possible.

The only way to hold it up is to stake it, using whatever materials and methods will be manly enough to do the job.

Without the tree rubbing. If there is enough weight involved you may have to have a permanent metal pole set in concrete installed, and secure the tree to it using straps.

I am in SC, too and have had Kousa Dogwood roots attacked by voles.
Do you see any tunnels or holes near the root system or base?
The voles may be a secondary problem to the sprinkler trenching.

stake it to within an inch of its life .... proper staking.. not tent staking ...

and invest in a new one.. and plant it properly .. ask if you dont know how ...

and watch the new one prosper.. as the old one declines ...

or end up with two ...

there is no reason the new one has to be of significant size ... meaning financial investment ...

though bboy is correct.. in that the only way to find out what is going on underground.. is to dig it up ... thats a real iffy thing to do.. on an already stressed plant ...

though the water guy may have impacted this tree ... the root of the issue ..... most likely ... was in the planting all those years back .... [there is a pun in there somewhere]

ken

ps: now lets get to the nub bboy ... i never heard of a turnip .. lol .. but if you were to be the one digging.. and you found your vast conglomeration of roots.. as you suspect.. would you mess with it.. or would you be done with it .... i think on some level ... i would continue digging.. and be done with it .. thereafter having the hole already for something else ... some things just might not be worth the effort ... [emotional attachment aside] ...... of course.. on 5 acres.. if this were 400 feet from the house.. i might play with it and see if i can rescue it ... but if it were by the front door.. it might be time to divest ...