Cutting of large root will either have a noticeably deleterious effect or not, all you can do now is watch the tree and see what it does. Regarding the equipment being driven over its other roots plywood sheets, wood chips or other protection should have been laid down before this happened.

You could try mulching with wood chips at this stage as the soil will soften beneath these over time.

Water the tree until the soil freezes. With less in the way of roots the tree will have more trouble getting water.

1 large root

Ambiguous description. On a 28 year old tree that could be 1" dia. or 4" root, big difference. A tree that size could weather a 1" root loss without skipping a beat but a 3-4" that branches out could make it show some shock or distress.

I hear you on the plywood. Not my property though, and the use of equipment went contrary to what I had been told.

Got it on the mulch and watering. Would a sprinkler be the best option? Say an hour each watering?

Root was probably more like 4" wide. :(

'Root was probably more like 4" wide. :('

Ouch. But I agree with toronado, best time year for this to happen when the tree is going dormant and what ed said about not letting it starve for water. Roots will elongate this time of year until ground gets too cold for growth. A healthy tree can recover.

Winter rains and any freezing & thawing of the ground (heaving) will help to return it to original state. If you can water the side not on your property if owner agrees.

Got it. Is adding mulch to the areas that don't have grass still a good idea, or will that interfere with the freeze/thaw you're talking about?

Another question: I know to keep mulch under 3 inches and to keep off the bark (no mulch volcano)... but what do you do about roots that have been exposed to air for a while and have developed bark? I've read that you should avoid covering those and just allow them to be exposed with no mulch over them. Correct?

it will be stressed.. not hungry.. fert is not a response ...

in TREE TIME ... you will find out ... and that could be 5 to 10 years from now ...

i really dont know the scope of a small excavator ... i would think a bobcat would be minor ....

if you consider a tree can be 2 or 3 times below ground.. as you see above ... and being optimistic.. one might think.. one large root shouldnt be all that big a deal ...

but its all left to fate...

ken

Sigh....okay still curious about adding mulch over roots that have been exposed to air and developed bark.

There are a couple of small lower branches that I had been meaning to prune back to the collar on the trunk. Will doing that now and just add insult to injury?

I'd skip the mulch. That was recommended for the compacted area and you confirmed that was not on your property.

Pruning a few lower branches shouldn't be a problem but wait until leaf drop or at least past peak color to occur.

Got it on branch cuts. The area in which they dug is an area that was previously mulched and that is on my property, but there's not much left. I plan to mulch it at some point. Since the dirt is so dry and exposed now, I was thinking that this would be a great time. Just concerned with roots that have been exposed and grown bark...

For watering, is something like an inch of water once or twice a week before the ground freezes the right amount? Probably taper off to once a week after the first week or two especially if it rains

Mulch is generally considered to be used for moisture conservation. This late in the season with shorter days and cooler temps, I'd just water it thoroughly and monitor the soil to keep it moist until colder weather arrives. Next spring new roots will start forming but all this takes ground that is not dry but moist.

You don't want to cover surface roots too deeply. A little coarse mulch like an inch or so won't hurt them. Was the area that was dug also compacted?

The mulch in that area had mostly eroded and the soil was fairly dry and a bit hard, but not otherwise compacted. They didn't drive over the area where they dug. Thinking of putting a thin layer of mulch there just to help hold the moisture, soften up the soil, and prevent rain from washing exposed soil away. I know a couple of you said not to bother, but it also just looks terrible right now. Unless anyone has strong objections that's the plan.

Also thanks to everyone for the info and suggestions so far.