Question: what are clay soil plants?
Answer: Iris. Iris species, including Japanese, Louisiana, bearded and more, tend to perform very well on heavy soil. ... 
Miscanthus. Ornamental grasses do very well in clay. ... 
Heuchera. ... 
Baptisia. ... 
Platycodon. ... 
Hosta. ... 
Aster. ... 
Rudbeckia.