A few questions:

How tall?

What habit (upright or fountain)?

Variegated or colored foliage?

donn, thanks for your follow-up - - tall? 2 to 3 feet, - - upright or fountain? both will work, - - perfer colored, maybe a beginning green and turning into fall colors - i love japanese blood grass but i am not sure it would work - maybe if i planted it in an appropriate terra-cotta pot - as you can see i do use sunken terra-cotta pots in other places in the potager - for peppers, herbs, garlic, etc.

thanks for your help, mr toad

I think Blood Grass is your best choice. I noticed the other sunken pots and it was the first thing I thought of. The real stuff isn't invasive, but it can revert to green, which is. The pot keeps it in bounds, and it's a gorgeous grass. I have several of them around the property, all in sunken pots, and I love them. For a nice twist, sow some Blue Fescue into a pot of Blood Grass. The contrast in color and foliage is excellent, and they get along well together. The Festuca gives the container a longer season of interest.