The evergreens will continue to get taller. And wider. And taller. And wider. So the spacing for where the additional shrubs can get tricky.

It is composed of alternating 10' tall blue spruce and arborvitae with yellow foliage.... I don't expect the evergreens to grow much taller,

size estimates. on conifers.. is at 10 years ... and at 20 years.. they will be TWICE AS BIG .. in every dimension ...

you are severely over-planted as to the conifers ...

and you say 30 feet wide.. how deep is the bed???

ken

I'm making shrub borders myself right now and I'm sure I planted way too close also but I guess that's a lesson that many of us need to learn the hard way :) Besides, things can always be removed later right? (lol, that's what I tell myself).
I like the various colors you chose and obviously it looks like a Spirea and a Barberry in the photos but it's hard to say what will work well in that spot without knowing the sun exposure. Also, do you have deer? Everything I plant has to be deer resistant (if there is such a thing-lol).
Im new at this too but I LOVE mixed shrub borders so your question is interesting to me. Good luck :)

I tried to keep my story short, but the evergreens don't actually look like this now. In fact, they're not even planted yet. With help from this forum (and you specfically, Ken), I chose some slow growing varities, so they won't be as crowded as it may appear. At some point it will probably be too much for this area of my garden, but with a growth rate of 2-3 inches per year, I won't be living in this house when it happens.

I'm creating the bed, so the depth will be as deep as I need it. I'd guess 20' would be ideal, but I could go deeper if need be. Now I have to figure out what shrubs to add to complement the evergreens so I can plant all of this in the fall. The area gets full sun. We don't have much of a deer problem, just a whole bunch of rabbits and chipmunks.

Privacy is often an issue with home owners. Many want to use plants, and want the screen sooner that the plants can grow.
I am not sure your computer photo is realistic for the space. Get a piece of graft paper and layout the plants to scale on the paper. Use the mature size. Monrovia list Picea pungens Fat Albert( a really nice blue spruce) at 10-15' tall 10-12' wide, so at best you have room for 3 -- if you allow adequate space. The real questions is when do you need the screen? Sometime a fence works quicker and requires less plants.
Try the graph paper and continue to research the mature size of plants.

Mike

Here is a link that might be useful: Garden Design Ideas

Unfortunately, my town does not allow fences higher than 4' without a variance, which I would never get. I live on a quiet street, so I don't need a full privacy screen, but right now it's an unobstructed view in to my back yard. 'Fat Albert' is actually the variety I wanted to incoroporate, but I'm worried about how large it would get beyond those 10 years. That area won't support more than one 30' x 20' foot tree.

It sounds like you are doing something similar to a bed I started in the fall of 2007 that is perhaps 70 feet long. I have 3 Fat Alberts as well as 2 golden arborvitae (Sunkist) and 2 dark green arborvitae (Techny) in a mixed border, and FA grows more like 6" a year for me in height and a bit more than that in width. I am figuring that I will need to remove the FAs eventually, particularly since they seem to be bothered by budworm. My other shrubs are larger than 4 feet, but my border divides two areas and so is viewed from all sides, not just one, so the evergreens are staggered throughout the border, not in a line at the back. I have some rhododendrons, a bunch of clematis on trellises or growing into the shrubs, several different hydrangeas, a couple of pagoda dogwoods, a few winterberry hollies, a rose, a clumping bamboo and a Coppertina ninebark. My goal was variation of color and texture of foliage (including winter interest) with flowers being the icing on the cake. In between the shrubs and trees and around the edges of the bed are various perennials, ranging in size from groundcovers to large scale perennials like Baptisia, Amsonia, and lilies.
December 2010 to give you a feel for layout of the evergreens
{{gwi:262165}}From December 2010

late spring 2010
{{gwi:197355}}From June 2010

Early this month:
{{gwi:262168}}From June 5, 2012

Some shrubs that are smaller in stature:
Ogon Spiraea (4-5'), lovely gold to chartreuse weeping foliage and white flowers in spring
Summer Wine (5-6') or Little Devil (4') Phsocarpus/Ninebark, both with reddish foliage
Cornus stolonifera/Red-Osier Dogwood: Arctic Fire (3-4'), Midwinter Fire (4-5'), rown largely for scarlet winter twigs
Deutzia Nikko and Chardonnay Pearls, both with spring white flowers and about 3', but CP has gold new foliage
There are a variety of shorter weigela with colored foliage, but Fine Wine is supposed to get to about 4' and has deep red foliage.
I imagine that there are plenty of Hydrangeas (particularly oakleaf/quercifolia and big leaf/macrophylla) that you can grow that don't exceed 4 or 5 feet, but I'll let you research those since my colder temperatures limit what Hydrangeas I can grow. I also like the H. paniculata varieties, and there are some that stay in the 3-5' range such as Little Lime and Little Lamb.
Rhododendrons: some of the Yaku rhodies stay under 4 feet, such as Yaku Prince, Yaku Princess, and Ken Janek. IME Rhododendron Checkmate looks like PJM, except that it tops out at about 3'. I'm sure that there are lots of other shorter ones that you can grow that I can't . The American Rhododendron Society has a database you can search with your preferences for height, hardiness, color and/or bloom time, linked below.
Blueberries come in half-high varieties that are usually in the 4' range and have spring flowers, summer berries for you or the birds, and stunning fall color
Another shrub with impressive autumn foliage as well as nice spring flowers and a tidy summer appearance is Fothergilla, and both Mt. Airy and Blue Shadow are in the 4-5' range.

Here is a link that might be useful: Rhododendron Society searchable database

Oh, I forgot one of my favorite shrubs - Daphne x transatlantica Summer Ice, which has delicate variegation around the leaf edges as well as ever-present flowers from before the last frost in spring up through hard frost in the fall. Not a stunning plant, just ongoing subtle beauty throughout the entire growing season. It's semievergreen and has been easy to grow so far for me over about 5 years.

Thanks, your bed looks great. A lot more than I'm planning on doing and definitely more than I can handle at this point.

The pH of my soil is 6.5, so I was planning on staying away from any plants that require an acidic soil. I think hydrangeas are the way for me to go. Any thoughts on the reblooming hydrangeas like Endless Summer?

I guess part of what I was thinking for your garden was that if you stagger the plants a bit, they will give good covereage, but won't become as overgrown for the space available as quickly.

I really like Endless Summer, but I've read some negative reviews from some parts of the country. My ES is just starting blooming now (most winters it gets killed to the ground) and will still have flowers forming when the first frost hits it. Nice bold leaves, but if your spot is in full sun, it will wilt back most days. Mine gets sun until about noon, and that seems to suit it. Check out what other reblooming macrophyla hydrangeas are hardy enough for your area. There are many more varieties now, with different colors, mophead as well as lacecap for the flower form, and the size range that can be chosen from is much more varied.

My Hydranea paniculata cultivars are in full sun and seem to do fine there.