I'd say if you've added 12" of good soil above grade, and the clay "starts at a depth of about 12" (below grade), you should be OK, especially if your soil test confirmed that the drainage is good in summer. My soil conditions are similar to yours (topsoil added over original grade, clayish soil at 6-12" depth below grade), and my Judd and Korean Spice ('Spice Baby') are doing fine. That being said, verticillium may be a concern if it is prevalent at your location.

Hi Joe, I'm in East central Indiana, and we have had quite a bit of rain over the last 10 days. This is a pic of one side of my backyard after the 'big' rain last week:

You can't see them from this pic, but I have two viburnums directly in that inundation flow. One is V. dentatum var. deamii, and the other is V. nudum 'Brandywine'. I can't get close to them yet, but I will try to circle back to this thread to let you know how they fared.

Indianagardengirl...yep, that's what my property looked like. I was in the heart of it last week, in east Central Indiana...one of the towns that was on the national news. We got 12+ inches of rain that day.

I do know that dentatum and nudum are more accepting of wetter soil. This location I'm talking about is a "winter wet" and "summer dry" location. West side of house with a slight slope towards the house...so it holds the snow melt and winter rains in that bed...but being on the west side it's blazing hot and dry in mid to late summer. A difficult spot to garden that's for sure.

Looks like we are probably neighbors ;). You may have to trial some just to find out. FYI in case you don't know it: there is a nice nursery up in Peru called Garden Gate. Every spring they get shrubs in quart size pots and sell them for about $15.99 (pre pandemic it was $10.99). Anyway, I have tried lots of things from them as I figure not much to lose at that price. It's brick and mortar only, and I usually make a pilgrimage every spring to see what they have. It makes for a nice day out if you're into that kind of thing.

Hi Joe. I would try testing the drainage in times other than the hot summer, too. To test drainage I (well, my husband) dig a hole 12-18" deep and maybe 6-12" across . Then I fill it with water and let it drain completey (could take a long time or maybe not). When it is empty, refill it and meaure how deep the water is. Then I measure again after ~15 minutes. See how far the water level dropped (with the ruler) and then multiply that by 4 to see how far it would drop in an hour (or just wait an hour and then measure). If the water has drained less than 1", you have poor drainage. More than 4" and you have very well drained soil. The sweet spot for lots of plants is in between those.

We have arell clay here in Alexandria. Poor drainage and hard as a rock in the hot, dry summers. Every year, I add compost to improve drainage. I sometimes work it about 6" into the soil with my pitchfork and some years, I just top dress with it (age and two knee replacements have cut into the amount of time I last in the garden-mostly the age thing as the knees are pretty wonderful now).

Good luck. Let us know what you decide to plant! ;-)