For tall grass's that are 4-5' in height, I suggest using the Miscanthus varieties. Although they are not evergreen, the flower heads in late winter are one of their spectacular features. I do cut them back early March each year to about 2' height but they quickly recover their presence in the yard. Miscanthus sinensis Gracillis and also the Miscanthus sinensis Strictus are good choices here.

Another option is the Switch grass, Manicum virgatum 'Heavy metal' It is 4-5' tall and also a spectacular garden specimen.

In the 3' range I suggest blue oat grass, Heliotrichon sempervirens which is evergreen in this areas. It is the clump grass center of the photo above.

The Siberian Iris is very attractive in the 3-4' range but you are correct, it is deciduous.

Although it is evergreen and very tough, I typically avoid the Pampas grass, Cortaderia. This is because it is miserable to work around the sawtooth leaves and it can become invasive in mild climates. It also looks very tropical.

I hope this helps.

Scott Lankford, ASLA

Thank you for your quick response! I will look into the options you provided.