There are many planted around here. Spreading vase seems to be the norm. Some are pretty broad.

There are a bizzion possibilities ...#1 you may just be getting use to the look #2 you amended the soil and it's gone way outside of it to areas less "friendly" #3 weather patterns have changed especially in Australia where they ( you) are having record drought those weather patterns can effect a tree with heat cold etc....And it may have other problems with it's root system or aerial pollutants ..yatayatayata.
If you could post ( if you have them) before and after pics it would help. If you are looking for pics one of our members Dax posted some nice S photos a while back ( this past summer I believe) that thread is here somewhere ...maybe if he reads this he can link you to it or post some new ones...David

>you amended the soil and it's gone way outside of it to areas less "friendly"Actually in organized tests of amending of planting holes using controls (blocks of plants without any amending) the less friendly portions were those amended. Growth improved after the roots of subjects in amended holes got into soil outside of holes. Subjects in unamended holes grew better than those in amended holes from the start. This pattern has been repeated multiple times on soils from sand to clay and using various kinds and combinations of amendments.

RE: "Actually in organized tests of amending of planting holes using controls (blocks of plants without any amending) the less friendly portions were those amended."

Can someone cite the authority for that propostion please? I have heard lots of people say 'controlled studies say not to amend soil when you plant a tree', and I'm sure there are studies to support that, but I'd jut like to read one.

At some point "amending" could become replacing the existing soil entirely and if the soil is replaced in an area larger than what the plant will ultimately colonize with roots, then certainly that could be a better environment in some circumstances.

I do agree that just adding some gravel or peat to the soil you just excavated and backfilling would probably do more harm than good, especially if you only excavate twice the size of the existing root mass.

But what if I excavate an area 20 times that size, and instead of amending the soil I replace it with whatever soil is ideal for that particular plant? Did they try that in the study?

I hope not because I planted a japanese maple in my front yard today and heavily amending the existing soil, actually my hypothetical was more accurate, I dug a gigantic hole and amending with composted pine bark and peat. I also planted several inches above the existing grade on a mound so hopefully that will mitigate drainage problems.