Most grasses are happy in most soils. We have Stipa tenuissima, but for a really tall one try Stipa gigantea. Have a look at the specialist website of Knoll gardens in Dorset.

Glad you asked this Laura! I'm also looking for grasses on Clay. I was thinking Stipa Gigantea too. I saw it first at Chelsea some years ago, and have always wanted to grow it as you get lovely flowers and seed heads at eye level or higher and it's a lovely colour..golden and shines in the sun. I think I shall have one of those! Yesterday I got three Unicinia Rubras at B&Q for £10. They had a good selection of carex, uncinia etc. all 3 for a tenner...worth a look! Unicinia Rubra is a smallish red/bronze evergreen grass. I love it!