Blue or gray soil is a serious flag for soil scientists. Clay soils are not always a problem in and of themselves; red clay soils are some of the most productive agricultural soils that exist. But gray means that the soil is without organic matter, without oxygen, and that the drainage is poor to non-existent.

I have a beautiful Styrax in my own backyard, planted in hard red Alabama clay. It’s thriving and we love it. If I had your soil, I would not plant the styrax. Amending the hole won’t help but if you could do something with the entire planting bed but that would be a big job.

Did you know that styrax is an amazing bee tree? You can hear the hum of bees from across the yard. And hummingbirds take baths in their rain soaked leaves.

look around the area.. do you see trees.. if so.. then trees will grow in clay.. presuming you dont kill it by improperly planting it..

watch a bunch of these.. until you feel confident enough to proceed ...

https://duckduckgo.com/?q=planting+in+heavy+clay&t=ftsa&iax=videos&ia=videos

i would plant it half above ground.. and use good draining soil on top to the clay to berm around the tree.. this insures that you have the proper drainage for the tree to survive long enough to work its own roots into the clay...

its the process of you messing up ma natures system by transplanting.. that will lead to failure...

and here is the usual general overview of the process..

https://sites.google.com/site/tnarboretum/Home/planting-a-tree-or-shrub

DO NOT dig a hole ..... and amend only the hole... it wont work ...

and good work on doing a perc test and gaining the most important info you needed to get the job done..

ken

Thanks for your responses. Yes there are trees all around. In this spot was a locust tree planted probably 20 ish years ago. It didn't look particularly happy and we took it out and ground the stump last year. Nearby is a sweetbay magnolia, and we seem to have lacebark elms along the street. If I want to plant anyting at all I will have to deal with the clay. And I can't give the tree back, I've had it for months (long story, hard to get landscaping done around here). So I'll give it my best shot. Plant it way high, berm it up a bit and spread the roots out horizontally as much as I can.

Oh, and it rained last night. Now the hole is pretty full.

Certainly bald cypress can grow in such soil -- it can literally grow in water. Dawn redwood perhaps can, but it will get huge & would have to take that into account. Also search for water-loving trees for a longer list.

Ken. One cannot make cookie cutter statements about trees. Some have unique reguirements, likes or dislikes. Styrax happens to require well drained soils and will no doubt suffer in heavy gray clay soil. I would not expect Zoe to see any other Styrax if she looks around the area.

Zoe has a good head on her shoulders and will do everything she can to help her new tree transition to a difficult environment. Gray clay is an indication of a lack of oxygen so she will have a challenge but not impossible.