Practically any tree or bush can be grown as a hedge when planted with close spacing and pruned as a single unit, although shrubs with dense growth are better suited for achieving a dense privacy hedge. You can plant new bushes to grow as a hedge; or if you already have a row of closely spaced bushes, you can prune them to grow as a single hedge rather than several separate bushes. As a general rule, spring is the best time to plant most bushes, but some bush varieties are best planted and pruned in fall.
Lay garden hoses on the ground to form the outline for the hedge row. Spray landscaping paint along the hoses to mark the outline on the ground. The width should measure at least twice the width of the bushes' root balls. Select a location that fulfills the sunlight requirements for the desired bushes or choose bushes based on the available sunlight where you want to grow a hedge.
Push a digging spade into the soil along the painted lines to begin excavating the space. Loosen the soil within the planting area to a depth of at least 18 inches, using a rototiller or hand-digging tools, such as a shovel, mattock or hoe. You must loosen the soil as deep as the root ball height, but shrubs adapt to transplanting more easily if you loosen the soil as deep as possible because shrub roots spread more easily in loose soil.
Mix up to 50 percent organic matter with the native soil if you have poor soil with few nutrients and slow drainage. Add a variety of materials, such as finished compost, aged manure, leaf mold, coarse sand and dried grass clippings, which help build soil tilth, improve drainage and add nutrients to the soil.
Dig a trench for the hedgerow within the excavated planting area. Dig the trench to the same width as the original painted lines and to the same depth as the shrub root balls.
Set the bushes in the trench while still in the containers to achieve the correct spacing for the hedge. Space each plant about 12 inches closer than the smallest mature plant size so the plants grow together to look like a single plant. Privet (Ligustrum ovalifolium), for example, grows 10 to 15 feet wide, so space each plant 9 feet apart. You can space them even closer together if you want the hedge to fill in more quickly, but they might require more frequent and more severe pruning.
Remove the bushes from their containers and gently loosen the roots along the outside of the root ball with your hands. Plant the bushes in the trench so that the top of the root ball rests even with the surrounding soil grade. Add or remove soil from under the root ball, if needed, to adjust the height and make the plants level. Back-fill the trench with the amended native soil around the plants, but do not pile soil on top of the root ball. Plant one bush at a time, filling in the trench with soil as you work your way to the opposite end of the trench.
Spread a 3- to 4-inch layer of bark chip mulch over the bare soil in the planting area, using a bow rake. Keep a few inches around each plant stem free of mulch. Organic mulch retains soil moisture and suppresses weeds that can compete with shrubs for nutrients and moisture.
Water the planting area until the soil is evenly moist, but not soaking wet.
Prune bare root, deciduous shrubs back to within 6 inches of the ground after planting. Use bypass pruners to cut the branches back on new plants. Do not prune bare root, evergreen shrubs.
Prune the hedge bushes annually in late winter and midsummer to maintain a uniform shape, using hand-operated or electric hedge shears. Cut about 2 inches from the ends of the branches at each pruning. Prune the shrubs to form a gumdrop shape with a narrow top and wider base. Push stakes into the ground at each end of the hedgerow to mark the desired width for the top; push additional stakes about 6 inches out to mark the width for the bottom. Use these stakes as a guide to trim the hedges evenly. Trim the top of the hedge to a point or dome, rather than flat, so snow doesn't rest on top of the hedge and damage the bushes.