If you're looking to create privacy or screen an undesirable view, a built structure — fencing or lattice — is the fastest solution. But surrounding your outdoor space with hard surfaces isn't always ideal, and many towns have height restrictions (6' to 8' max per most building codes) that prohibit the kind of blocking you actually need. Happily, there are plant-based screening solutions for just about every situation, whether you want an intimate outdoor dining area or need separation from your (overly) friendly neighbors. From trees to shrubs to hedges, natural fences offer plenty of protection, not to mention texture, color, insulation, and, most of all, beauty.
Privacy for a seating area without blocking off views: Tall ornamental grasses in raised beds or planters
When you're seated, you only need about 5' of greenery around you to feel ensconced and unexposed. Grasses are ideal for surrounding a dining or lounging area since they top out around that height and won't block distanced views or create too much shade. For a patio or terrace, grasses in decorative planters can help define the space. Choose calamagrostis "Karl Foerster" (pictured above), known as reed grass, which has a feathery look and reddish-brown color in the spring, if you're aiming for an upright effect. Panicum virgatum (northern switchgrass) or miscanthus are tall but more fountain-like in habit. All are fast-growing and will reach heights of 3'to 4' by mid summer but they do need ample sun to thrive. While grasses will give you coverage most of the year, keep in mind there is a period of exposure in late winter/early spring whey they must be cut back to promote new growth.
Privacy for an outdoor space from neighboring properties: Mixed evergreen and deciduous tree + shrub border
For many of us, spring and fall are the most important times of year to ensure we have ample outdoor privacy—in the winter we are mostly holed up indoors and during summer abundant leaves often do the trick. That means you should take advantage of seasonal splendor in your screening plans and not limit yourself to an exclusively evergreen palette. Mixing heights, colors, and textures with some repetition for cohesion will create a dense tapestry of green with dimension and movement that feels more natural and pleasant than, say, a straight hedge of just one type of tree (a row of arborvitaes, for example). Here are some of my favorite combinations:
Betula nigra, or river birch, for fast growth and upward-reaching habit—it's willowy branches and small leaves are great for movement and texture, and it's yellow fall color plays beautifully against darker greens;
Cryptomeria japonica for fast growth, height, year-round green, and unique texture;
Skip laurel for medium height and bushiness—it's evergreen and has lovely dark foliage that makes a good foil for brighter greens and flowers;
Magnolia virginiana is evergreen with lovely fragrant flowers in summer and a nice narrow, vase-shaped habit;
Amelanchier canadensis (serviceberry) for medium height, early spring bloom of prolific white flowers, and excellent fall color—I love the way it's grey bark attracts the light and how it naturally grows into a vase shape [not sure if this conjures the right image].
Screening Utilities: choose mid-sized evergreen shrubs that take well to pruning
It's nice to have year-round protection from unsightly HVACs, propane tanks, and other utilities. The most space-savvy and instantly effective approach is a hedge of mid-sized evergreens. Aim for fast-growing varieties or extra-large sizes of slower growers to quickly establish the a "fence" around whatever it is you'd rather not see. Choose shrubs that take well to pruning so that appropriate space can be maintained between them and the equipment they hide (technicians need easy access to equipment and you want to prevent branches from growing into or blocking vents or openings). The best choices are bushes with an upright manner, such as Blue Point or Spartan junipers, skip laurels, and ilex Sky Pencil.