I had it tested and found just the right amendments to make the soil drain, and let the roots expand.
My clay soil had to be amended as follows:
1/3 part existing soil
1/3 part perma- till
1/3 part mushroom compost
Dig the hole twice the width of the plant root ball, and a few inches deeper.
Blend the mixture well, add 3-4" to the bottom of the hole and tamp to remove air pockets. Place plant into the hole, and add prepared soil around the plant. Tamp as you go. When planted and mulched, place hose at the base of the plant and water well.
If you do not receive about an inch of rain weekly the first year, it is a good idea to water.
A good saying to remember here in the south is "plant high, they won't die...plant low and they won't grow." That is because the clay soil acts as a bowl and the plants will drown if they don't get the proper drainage.
And don't forget to mulch. A 2-3" layer will keep the temperature in the soil more consistent and will also keep the moisture in the soil longer.