Shrubs As Barriers

Security Barrier

• To discourage trespassers or to provide additional security, consider shrubs that have dense, impenetrable branching and that have spines or thorns. Mentor barberry (Berberis x mentorensis) reaches about 6 feet tall and as wide in U.S. Department of Agriculture plant hardiness zones 5 through 8. Chartreuse new foliage turns blue-green in summer and yellow to wine-colored in fall. Thick stems and branches bear single and clustered spines, making a thick barrier that extends to the ground. This hybrid originated in Mentor, Ohio. For mild-winter areas, natal plum (Carissa macrocarpa) has dense, leathery evergreen foliage and stout branches armed with forked spines. It grows in USDA zones 9 through 11 and has fragrant, star-shaped flowers followed by red, oval edible fruits.

Visual Barrier

• Visual barriers can be more open-branching as long as they provide layers of branches and foliage that screen the view. If you need year-round screening, use evergreen barrier shrubs such as Hick's yew (Taxus media "Hicksii") for its fine-textured dark green foliage. Growing 12 to 20 feet tall in USDA zones 4 through 7, female bushes bear red berries that attract birds in fall and winter. Classic myrtle (Myrtus communis) grows in USDA zones 9 through 11 and provides fragrant evergreen foliage, starry white flowers and waxy oval blue berries that attract wildlife. Allow plants to grow naturally or clip them into hedges. Growth is usually 6 to 8 feet tall.

Wind Barrier

• Shrubs can form one component of a wind barrier belt of trees and shrubs, useful if prevailing winds limit what you can grow. Evergreen or canopied trees give height to shield upper-level air flow, and shrubs fill in from ground level to where tree branches begin. Texas A&M University cites a 23 percent reduction for homes sheltered by windbreak vegetation. Dense, evergreen shrubs work well to restrict wind flow. "Blue Point" juniper (Juniperus chinensis "Blue Point"), grows 12 feet tall and 8 feet wide in USDA zones 4 through 9, and "Emerald" arborvitae (Thuja occidentalis "Emerald") reaches 15 feet tall and 3 to 4 feet wide in USDA zones 4 through 8.

Boundary Definition

• Within your yard, plant barrier shrubs to delineate usage areas. Wall off a utility area or work space with dense shrubs that give visual screening. Create a low barrier to set off, but still allow views of, the herb garden. Species of lavender (Lavandula spp.), generally hardy to USDA zones 8 through 11, make a fragrant and tidy choice. Podocarpus (Podocarpus macrophyllus), hardy in USDA zones 7 through 11, could be constrained with pruning as a barrier hedge to create privacy for a narrow yard. Its evergreen foliage and tolerance of trimming lends itself to formal and informal applications.