This is a long thread I just stumbled upon so I didn't do my due diligence and read through all the comments to see if my recommendation was already suggested so please forgive me if it was. I would plant 'American Pillar' Arborvitae along the entire fence line and give it a couple of years. It's cheap (I found them for $7.50 a pop for an order of 100 plants last year), narrow (3-foot at base when mature), tall (30-foot max), fast (3-foot per year, once established), densely evergreen (no see through branches), cold hardy (to zone 3), disease free and long lived (no known problems with a lifespan of it's ancestors measured in centuries). What more can one ask for? Here is a link that might be useful: American Pillar Arborvitae

Sorry; I was wrong about thinking that the Corintian Rose and Mauve cultivars as being new developments. Did some checking and now realize that a few years after more nurseries began offering the Ornamental trees, I must have seen a photo of the Corintian Rose which appeared to bloom more red colored. But the latest photos I have seen of the Corintian Rose seem to reveal that tree's blooms being more true to what reported descriptions of it have been turning up. Dr. Dennis Werner had successfully developed these Corinthian peach cultivars, and reports of them started showing up in web perspectives back over the winter of 1998-99. Those perspectives projected that nurseries would be making these trees available by the winter of 1999-2000. I have not seen the standard nurseries in my area offering these trees, but after I inquired about them to my favorite nursery on the northwest edge of town. They fairly easily found some being offered to the wholesale markets from a local regional grower. My extra research about the development of the different cultivars has reminded me of what I had obviously forgotten when I posted what I replied above. The truth is that Back in the winter of 1998-99; the cultivars which had already been developed were Corinthian, White, Corinthian Pink, Corintihian Rose, and Corinthian Mauve. With the Rose and the Mauve cultivars just now showing up more often on various web sites, must mean that now those cultivars are catching the eye of people more than the White and Pink cultvars are right now. One thing I do know is that the photos on the web of these trees do not capture the dynamic beauty that one is surprised to see in any of these trees that are thriving out in their planting beds. Must be something about the camera shots being so far away that the size and shapes of the flowers appear more non-descript in the photo's and also the amazing way that the sun make the colors of those flowers to appear so stunning must be an aspect that the camera's missed capturing in those photos of these trees that I have been more recently seeing on the Web. I know that the Pink cultivar blooms certainly are such, simply because a friend of mine planted four of these trees along the narrow strip along her front driveway and that boarders her neighbor's yard. The first Spring that her trees burst out in bloom, her husband who never seems to say much about the items at her house that we have planted, well even he, was taken aback at the sight of how stunning those blooms were. At first sight he rushed to get his camera and quicky attached that photo to an email and sent it to me to let me know how amazed he was at first sight of those tree tree's bloom. That was 3 years ago, and the only other item he has reacted the same about was after he first saw blooms, on the hardy, Blue Satin Hibiscus that I had trained up in a tree form and helped my friend plant at her house. Those clear blue...

Emerald Green Arborvitae seem like the most common mainstream product for your type situation. Be mindful there are options, like Yellow Ribbon Arborvitae, in case you like yellow golden blaze on your green. Smaller trees will establish faster. You probably don't want to buy at a store parking lot where they sit in little black plastic pots baking in the sun, during the heat of summer. Single leader is often recommended because non-single leader Emerald Greens can splay out under snow loads, and may not fully recover their original shape. If you plan arborvitae, read up online on an awful little creature called a bag worm, because they can creep up on you and a horde can do a great deal of destruction to a stand of arborvitae really fast. Some damaged a Colorado Blue Spruce bush form of mine last year, so it's not just arborvitae. Bayer Advanced can be your friend. It's easier to kill these things before they get big, I'm told. Emerald Greens aren't the most drought tolerant things while getting established; if your summers get hot & dry, expect to do some watering. Some people like the look of a one species/one cultivar row of trees. Some people like variety and the reduced likelihood of a one pest wipe out that comes with a mix. Some other modest size conifers include Boulevard False Cypress (not the topiary 'poodle cut' versions) and some dwarf cultivars of Colorado Blue Spruce, like 'Baby Blue Eyes' (which I think is different from Baby Blue). See if they are thought to do well in your area. Some holly trees might provide variety; holly comes in male and female forms, and only the females make the berries, and need a pollinating male in the area to do it. While there's no guarantee a tree will stop growing at a particular height (in fact, it likely won't), this might be useful info. Richard.

I would strongly recommend attaching lattice to the top of the fence and getting a vine to grow there. Look for something evergreen like Carolina Jessamine. I think the area is too narrow for any kind of small tree unless you went with something like Italian cypress, but those get way too tall for what you need and will eventually get about three feet or more across. I look at it this way. It is a rent house. You probably won't stay there long enough to get any benefit from planting a large shrub / small tree since no matter what kind you plant, it will take a few years for it to grow and fill out properly to create the screen.