Chelle unless you can find a shorter type, I think it would be to large in a rock garden. Mine is
Baptisia australis and gets 3 to 4 feet tall in full sun and is planted near a fence to give it some support. I usually trim it back some after it blooms to keep it from shading out other plants.
Added: I looked mine up and it gets 3 to 4 feet across, mine could be that size. I have never measured it as it has room where it is planted.
