It amazes me that a nursery will sell such a big tree at this time of year to be transplanted. Not your fault - I hope the nursery gave you a warantee. In my opinion, these trees should have been planted one month ago or, better yet, in September and beyond. The summer is too hot and tree physiology is working in the top of the tree now, not in root growth.
About planting - clay soils should be fine for blue spruce - just so long as the ground is fresh and not saturated for long periods.
Try to orient the tree facing the sun the same way it has been grown.
Loosen the soil around your hole, add 1/4 of a hole full of water and allow it to settle in. Add tree and gently pack roots 360 degrees around tree to provide future support in all directions, and eliminate air spaces. Water moderately.
For trees 8' tall, you will want to cable them on three sides (120 degree angles) for support for this season to the spring of 2003 (June).
Good luck. Wear gloves - they're sharp!
