We have clay under 6" of topsoil. I found it's best to dig after a good long soaking rain. If the clay's dry it's pick and shovel time and slow going. I tried to remove the topsoil and soak with a slow dripping hose over two days but that was not very sucessful. Rain's the best. With today's rain and showers predicted for the rest of the week you may be able to dig fairly easily later this week. Good luck. Also remember that you've dug an impermeable bowl that will trap water and possibly drown your trees. It was recommended that you use the soil dug up and not add ammendments just for that reason.

After the rain, it is easier to dig. The planted ones are doing well. I did not amend the soil and they are on a slope.

I too have unbelievably hard clay. I gave up digging those clay pots years ago and started planting on top of the ground. I cover the area where I want to make a garden with several sheets of newspaper and free woodchips from the town about 8" high. Then I make holes for whatever I am planting, put a soil mix in the hole and plant. It has worked well and eventually the woodchip mulch turns into a great soil, drains pretty well and roots grow easily into the mulch. For trees and shrubs alone, not in a bed, I build a mound and plant in the center. Good luck. bobbi