It's hard to tell how much space there is, but the first spots that strike me would be between the window and the corner of the house, something tall and erect. Then, to the right of and behind the tree, maybe against the fence, something tall, with a fountain stature. A window planter full of Blue Fescue would look great, as well.

Lovely flowers!

Calamagrostis "Karl Foerster" and/or Northern sea oats Chasmathium (not sure of spelling on that one.) These are two of my favorites.

Muhlenbergia japonica variegata, Deschampsia Schottland, Chasmanthium latifolium, Anemanthele lessiona.

Looks like you've had a few suggestions to weigh already. I'll toss out a suggestion for a Molinia of some variety. Molinia is also known as Moor Grass and I find that it adds a beautful and subtle quality to my part shade garden. You'll want to choose a variety that will not be totally swallowed by the rest of the plants. Molinia caerulea subsp. arundinacea 'Skyracer' will get quite tall with a basal clump maybe 2-3 feet tall and fine airy flowers that shoot up some 8 feet. Molinia caerulea 'Moorhexe' is smaller and very narrowly erect. These grasses are more subtle than most and are generally hardy to Zone 4.

Something to consider -- do you water that bed at all during the summer? Molinia flower more reliably if there is at least some moisture. They flower mid-summer.

Another grass group to consider would be Deschampsia cespitosa for its early flowering, hardiness to Zone 4 and attractive qualities.

Finally, consider just putting a less hardy grass in the middle of that garden in a container each summer. that way, you can try on different ones and play around moving them to maximum advantage. With all the other stuff coming up the container would be hidden but not the grass. Pennesetum setaceum 'rubrum' is amazing in a larger container where it has room to get bigger over the summer. Beautiful burgundy blooms that last all summer once they begin. Would make a fine statement in your garden.

Thanks for all the ideas!

Since I'm totally new to ornamental grasses, could someone explain to me why I don't need to worry that all those pretty little grass seeds will seed themselves all over my garden?

I went to two local nurseries and they couldn't assure me that this wouldn't happen. I liked Panicum "Shenandoah" and others with dark red blooms.

That bed, by the way, is much larger than it looks in the photo and gets watered.

Panicum virgatum 'Shenandoah' or 'Hanse Herms' would be a fine choice in my opinion as long as there is enough sun. They like full sun but will take somewhat less. Red tones are best with more sun. These cultivars are generally not known to be prone to self-sowing as the species is on moist open ground. Lovely grasses.

You donÂt need to worry about seedlings in zone 4, especially with the grasses recommended to you. Your settling in on Panicum v. 'Shenandoah' is good regarding hardiness, height, texture, color, flower. (Forget the MuhlenbergiaÂnot hardy in zone 4. The other suggestions are good, too, though.)

BruMeta, not to bust chops, but I have had successful trials of clients in zone 4 settings with both M. japonica and M. j. variegata, with heavy mulching, gertile ground, and sunshine during the growing season that present the original plant coming back.