When I did a privacy barrier between my neighbors and me at my other house, I used a row of Arborvitae "Emerald Green" as an evergreen screen. I chose this one because it purportedly is more resistant to browing in the winter. I was really pleased with the purchase - they were lovely and really did stay green in the winter. I did keep up with the trimming yearly, though, so they didn't get out of hand, and mine were around 8' or so, maybe a little shorter. Of course I jazzed up the area in front of it for my viewing pleasure with misc. perennials. Don't remember what off the top of my head, but I do remember that I planted a "Bloodgood" Japanese Maple in that area, and the deep red leaves played beautifully off the rich green of the Arborvitae.

So, if you do an evergreen screen, make sure to include a least a smattering of colorful foliage perennials or colorful shrubbery, or all your eye will see will be a solid wall of green. Red twig dogwoods would look great against an evergreen backdrop in the winter, for instance, or a red Japanese maple.

Sedums 'Autumn Joy', 'Autumn Fire', 'Purple Emperor' (with purple foliage) always look good with grasses and Perovskia (Russian Sage) and have that rounded look you want. A nice little shrub is Diervilla 'Summer Stars' with a soft, slightly chartreusey yellow summer bloom. Another domed perennial, though quite large (4x5) is Baptisia 'Purple Smoke' with great late spring bloom and a very handsome look the rest of the season.

Achilleas aren't really domed, but they are flat headed. Two of my favorites are 'Terra Cotta' and the slightly later 'Fireland' (Feuerland).

I did exactly the same thing as mxk3 - I had a gap in the border along the north side of my property - which is pretty close to the neighbor's kitchen porch. I wanted privacy and screen from their porch so I put 7 Emerald Green Arborvitae about 4 feet from the actual property line. The Arborvitae will serve as a green backdrop for assorted shrubs and perennials I will plant in front of the Arborvitae.

I planted the Arborvitae about 4 feet apart on center. This cultivar grows about 4 feet wide and 12-15 feet tall, so they don't get too large and won't block the sun my neighbor's enjoy on their porch. I don't like things growing in a straight line like soldiers so I planted them in a subtle zig-zag pattern. Also I used two different heights because I like the undulating effect. The one in the middle was a replacement for one that died so it is shorter. These will fill in so they will touch and with a little pruning should become approx. the same height.

Nice thick evergreens like Arborvitae have the added benefit of providing cover for birds, and I noticed while watering them last summer that lots of moths like to hide out in these during the daytime.

Here's a pic:

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As for grasses, they are many beautiful tall grasses you can mix in your border. However, grasses need to be cut down in the Spring so they only provide screen for about half of the year. They also get BIG after a few years and more difficult to move and cut down.

Some of the taller species:

Miscanthus spp. 'Variegata', 'Gracillimus', 'Morning Light', 'Zebra'
Calamagrostis 'Karl Foerster'
Panicum virgatum - Switch grass, taller cultivars like 'Cloud Nine' or 'Heavy Metal' or 'Dallas Blues' - this is a beautiful native tall prairie grass
Sorghastrum nutans - Indian grass, another gorgeous native tall prairie grass

Here is a pic of some grasses I have in the front along the street:
{{gwi:194442}}

Sorry, dotchkey, re reading your post I don't think you were asking about grasses - just that you were keeping a few you already have, so ignore the grass stuff if it's not relevant!

Also for evergreens I have a pretty dwarf Norway spruce, that was previously used as a live Xmas tree in my front border and it is very slow growing, tidy looking, and maintenance-free. You could also use a dwarf Alberta Spruce.

I have a very similar border that runs alongside my driveway, which is more than 150 feet long. My plan is simple, but I am surely enjoying it. The design has two rows of shrubs in a five to six foot long border that edges the driveway.

ROW ONE:
First, I planted dogwood trees, about every 15 to 25 feet along the neighbor's side of the border strip. (spring bloom, fall color, nice winter structure, will top out at 25 feet). Between those trees, I planted dwarf burfordii hollies (deep evergreen color, winter berries, slow growing, barrel shaped, will top out at six feet or so), which I will eventually be clipping into a four to five feet high hedge.

ROW TWO:
Then on my side of these trees and shrubs, and centered between the street and the back of the driveway, I planted a row of a dozen Endless Summer hydrangeas, underplanted with spring flowering bulbs. (These give me continual bloom all summer long and break up the line of azaleas that are on either side of them. Also, the bulb foliage puts some green in that naked area during the winter.) From the street to the hydrangeas, and from the other end of the hydrangeas to the back of my driveway, I planted a row of Coral Bells azaleas (also in front of the hollies and dogwoods). They give me an oh, so southern, burst of bright color in the spring, some nice fall color, and structure the rest of the year.
Now, I realize that perhaps none of these plants will flourish in your area, but perhaps you can find some plants that do grow in your area that will fit some of the design principles: multi-season color, evergreen structure, and look nice both from your side and from your neighbor's side.

You could try a dwarf hinoki cypress (Chamaecyparis). They come in many different cultivars, I like them a lot. Try this link, it may help you decide what you like and dislike.
Sarah

Here is a link that might be useful: This site has a bunch of dwarfs to look at.

I think the recurring theme here is repetitiveness i.e. consistency. If you use one plant or shrub for your background (like the evergreens) it goes a long way to making the area look tidy. In front of them, use shorter perennials than the background plants. What has worked for me is to repeat themes of plants that you gravitate to or tend to do well. Limit the amount of plants you use and repeat them periodically down the bed. It simplifies the look and avoids a mish-mass of individual plants which always makes things confused and messy.

Thank you for the advice everyone. With everyones suggestions I think I've come up with a pretty good plan. I think the "mish-mash" of stuff I have is the problem! I've collected so many types of plants over the years but have never spent the time on design. Hopefully I wont have to spend too much money. I'll take a bit of everyones advice and I'll group some existing perennials in 3's and repeat down the border and add a few dwarf conifers and/or maybe some inkberry hollies and make a screen with some tall evergreens (possibly Arborvitaes)and my grasses. I'll get a good start with what I already have. And I'll have to break down and maybe get rid of some the 'extra' perennials - or maybe even start another garden!!

On the other side of my house I created a smaller property border with Arborvitaes, variegated dogwoods, rhododendron purple gems and hydrangeas. It's filling in pretty nice. I guess I can follow the same design idea on the other side of the house but just bigger.

Dkotchey,

Sounds like you have a lot of tall plantings and that very short Coreopsin Moonbeam in front. Don't forget to put something kind of "medium" height.

As you can tell by my user name, I'm very fond of hostas. A Sun Power hosta down in your sunny end and a Plantaginea hosta in the shady area would be very nice, imo! Both get fairly tall and the Plantaginea has nicely scented flowers! Sun Power is a very pretty gold and has a very good growth rate.

Char