A first reaction is that your tree probably isn't girdled, but has four main roots flaring off of the main trunk at equal distances apart - giving it a square appearance at the base. The only answer to discover girdling is to carefully excavate the soil at the base of the tree and look. Some arborists actually use an "air spade" to check for girdling that literally blows the soil away from the base of the tree without doing much damage to the outer root covering.
hortster

i would love to see a picture of this ...

i cant really fathom how a CIRCLING root .... would cause a trunk to become square .... unless there is some square collar buried down below.. but i cant even think of a reason for a square collar ...

this tree has been there since ONLY 2007 and is already 25 feet tall .... tell us more about the project .... and installation ...

ken

Why not carefully/gently dig down a little with a small spade or trowel and see what you find? You should be able to see a root flare without digging (or at least without digging very far at all). Especially without even seeing it, we can't give you any definite answers about what is causing the problem (except that it doesn't have anything to do with your mulching practices, and, as Ken alludes to, if the trunk is square, it won't be because of a single circling root). Now is as good a time as any for this. If you're physically able to to some light digging, there's probably no need to hire someone for an initial look. Depending on what you find, a certified arborist might be able to advise you further down the road. Post some pictures of what you find for more Gardenweb input.

I'm not inclined to think girdling either. Nor am I inclined to give diagnoses without more information. But as hortster said, there are other reasons for this as well, and I'd use an air spade before I'd start digging.

Dan

Even if the tree dies its not a sign the landscaper did anything wrong. Like ppl some trees just don't live as long as others. Transplanting large trees is difficult on them. Impossible to get all their roots.

Does the tree leaf out as thickly as others around it in a similar amount of sun?

I'm patiently waiting to see my first square trunk.

If there are square watermelons, why can't there be square tree trunks?

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Sorry for the delay. I'm posting pictures, but they won't be of much help, I fear. I took a friend out with me to photograph this, and his conclusion was that it FEELS completely flat on two opposing sides, but you can't clearly see the squareness (so maybe it's whatever shape is flat on two sides and a little rounded on the other two?!) I can't post feel. The third picture almost shows the flatness of the trunk. As for the height, I've taken two photos from the second-story deck that might help a little. 25 feet is indeed a guess, but you can see how much taller it is than an 8-foot obelisk (the obelisk is black and in the foreground, tough to see) and compare it to a weeping Alaskan blue cedar. The property slopes steeply downhill behind these trees to an alley below, which is much less apparent in the summer. Hope this helps.

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i dont see any root flare .... that does need to be remedied ....

where the soil meets the trunk .. you ought to be able to see the demarcation from trunk to roots ...

pull back the mulch.. and then the soil.. and figure out how far too deep they planted it ....

ken

Yes: definitely too deep. If you dig down and find many new roots coming out in response to existing soil depth, stop the uncovering as tree has already survived being buried too deep and made an adjustment.

Container-generated root deformities are pandemic among nursery grown plants here, I'd be surprised if all your trees had perfect roots. Plants coming out of a field is no assurance that they are not rootbound at all, as such stock may often have been planted out into the field from liners, bands or pots.

Finding the tree putting out new roots in response to being planted too deep, doesn't mean the tree has overcome potential problems. It only means the tree is making adjustments. Although it could be a good sign, it definitely doesn't mean the tree is home-free. Roots planted too deeply and the root collar/crown and trunk of the tree may rot causing problems as serious as the death of the tree.

Do as Ken and I have suggested and explore a little. At least rake the mulch back and remove soil until you see either signs of the root collar/crown or decent size roots. Post pictures of what you find. All the pictures above show is that the tree is either planted too deeply or has a deep layer of mulch around it (which I think you said it didn't).

We see this around here a lot with the Gleditsia: planted too deeply, the trunks get the cavities or whatever that flattening is. Then the Ganoderma or other pathogens kick in. The plant lives 4-5-6 years, then croaks in a hot summer.

If the top 4-6 in. of soil was not removed from the ball when planted until the top roots were found, too deep.

And 'experienced LArch' means squat to me. I made good money in CA cleaning up after them.

Dan

Yes, theoretically a tree could be deteriorating at the same time that it is re-rooting at the new level. But I'd think if it had lived long enough under the new circumstances to make a significant amount of new roots at a higher level that could be taken as a sign that it might have gotten through a critical phase.

And if you kill these newer, higher roots trying to return it to a previous condition then it will have suffered two phases of difficulty instead of one.

Some trees are native to floodplains and are not as prone to damage and death from sudden changes in grade as others.

Great input! I appreciate all of it. I'm in the middle of hand surgery, as luck would have it, so I truly can't dig far, but I brushed all the leaf litter away (and there was a fair amount this time of year) and went down a little further with my hands. I think I found root flare. See what you think from the pictures. That leads me to believe the tree might be planted an inch or so below grade -- although this is a slope and the pictures are on the downhill side so the uphill side may be more buried.

I failed to answer someone's question about its apparent health during the summer. It has grown like a weed and has leafed out beautifully each summer. The canopy was skimpy the year it was planted, but about a month or so after leafing out last summer it suddenly had a mature canopy.

Here are the pix:

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The pictures are good pictures, but I can't really tell exactly what I'm seeing. What is that light ring around the bottom? Is that just a clean area or something else? In the first picture, it look like that area may be bulging, but it may just be the root collar.

It does bulge a little. Is that inconsistent with its being the root collar?

From what I see it looks like hortster's original thought of four main roots flaring out is correct. With the tree being healthy otherwise, I'd not worry about it. At most maybe expose the root flare on the other side.

tj

As long as the bulge is not a girdling root I'd say TJ is correct about being sure the upper part of the root collar is exposed and then not worrying any further. I see nothing that corroborates or contradicts the four root theory, but it doesn't really matter as long as the tree is healthy, the root collar is not buried, and there is no sign of girdling roots.