guys, we really should not chat about other stuff on these Ask a Question threads:
it says this in the green notice above:
Keep in mind: your post may trigger an email to the original poster, so please keep on topic!

End of argument, huh?

RickCorey said:But maybe if the amendments are tapered off gradually, roots will make the transition from the improved soil to the unimproved clay.

It probably depends on the tree, the clay, the site and the gardener. But I would trust people with "tree experience" more than me.

I no longer give a lot of weight to "Internet consensus" about gardening matters.

Here's the thing...

It isn't just "Internet consensus" .

I have it straight from the local extension service.

When we add amendments to the planting hole (or replace the soil), the soil in the hole stays wet in the winter, and dries out in the summer.

When we're dealing with a tree like ginkgo... pretty much need respect the need for drainage, which isn't happening when digging a planting hole in a clay yard.

When I plant fruit trees... I take my own advice (plant in vegetable garden), whether gardening in clay or sand...

I've planted a lot of trees for paying customers... and whatever gets planted in a packed clay suburban lawn generally doesn't grow much, in spite of the size planting hole I've dug...

Although... fast growers like tulip popular, Paulownia, and box elder have grown well enough to warrant 2 of the 3 being cut down in one yard... Of course... there was a lot of mulching (wood chips) every year with the turf being dug back and back and back...

I totally agree that any hole dug below-grade in clay NEEDS drainage supplied one way or another.

I guess you could call a drainage ditch a long, shallow, amended planting hole, if it was back-filled with something permeable to water and roots.

Avoid this:

Pan,

I'm going to go off a little of the tree subject here, as I am not prolific about that. I have killed too many to brag about. I'm going back to your butterflies.

I tried growing citrus trees here, all grafted on hardy root stock. I was too ignorant to know you had to protect that above the graft. Anyway, the grafted citrus froze in the first harsh winters here. However, the root graft grew and attracts giant swallowtails every year. So growing any citrus will bring these butterflies. If you have gulf frits, you should also have zebra long wings as the passion vine is the host for both.

I have tried keeping the host plant for the monarchs, but they always die, so the monarchs don't come here.

It is such a pleasure to sit out in the gardens and almost have the butterflies rest on your shoulders.....