If you have walls or fences on your property, you may want to consider adding some variety to their surfaces. Wall-covering plants break up the vast expense of surface and may enhance the aesthetic value of such a wall or fence.
Wall-covering plants may be either trailing forms planted above the structure or climbers placed at the base and allowed to grow up and over it. Either way, plants soften the hard surface with their foliage and flowers. In winter, the changing shadow patterns from the exposed stems and branches create additional interest.
You need different plants for each type of wall or fence in the garden. Tall retaining walls need long-reaching shrubs and vines that droop downward several feet to cover the bare expanse. Low walls, 3 feet high or less, can be handled in the same fashion, but with less vigorous plants. Freestanding wood, brick or stone fences benefit from vining plants that climb up and over one side and cascade over the other side a foot or so.
Keep in mind that most vining plants tend to be vigorous growers and will need regular attention to keep them within the bounds you select. They should be compatible with other plant forms used nearby. If there is any concern about the vine escaping into surrounding shrub beds, it is suggested you remove or relocated the shrubs well away from the vine.
Weeping Forsythia — Forsythia suspensa — is a possible choice for softening high walls and exposed banks. The stems grow eight to 10 feet as they extend from the plant and trail along the ground. The plant itself is generally about 5 to 6 feet tall. Early yellow spring flowers are similar to those on shrub forms of forsythia. Summer color is deep green. The arching stems help stabilize a bank where they touch the soil and root.
Another choice might be Virginia Creeper — Parthenocissus quinquefoilia. This vine has supple stems that attach directly to the wall or other surface. If suspended over the wall, stems wave in the breeze. Flowers are of no ornamental value, but the subsequent deep bluish fruit contrasts very well with the deep crimson fall foliage. The intricate branch pattern adds winter interest. This is a rampant grower and needs regular attention to keep it where you want it.
Climbing roses with their long arching branches are another choice for softening tall walls. Rambler roses, with their flexible stems and masses of small flowers, also work well. When planted along the top of a wall, they generally grow along the edge, with some of the branches flowing over the top. Rambler roses and hybrid clematis make a good combination.
A number of flowering vines will grow well along the top edge of freestanding fences. The dense vine growth adds a “cap” to the wall and continually changes color and texture during the seasons. Any variety of clematis would be a good choice. Because it has no support mechanism, this vine will need strings or wires for vertical support on the surface of the fence until it becomes established.
What if there is no planting space at the top of a wall you wish to soften? In this case, there is nothing wrong with setting a moderate shrub border at one end or the other of the wall to break the expanse. Don’t attempt to completely cover the wall with shrubs — or vines for that matter — because it creates a monotonous green covering of the surface.
Softening lower walls with plants is a bit easier to accomplish, and you have a wider range of plants to select from. If you wish to use a vining plant, English Ivy — Hedera helix — is an evergreen that does well in many areas. In very cold, exposed sites that face south, some of the stems on the wall surface may be winter killed, which might be looked upon as a form of natural pruning. The plant never becomes too invasive, and the ivy’s growth is strong enough to replace most winter injury. However, the ivy attaches itself directly to a surface with rootlets, which may damage valuable surfaces.
Several of the evergreen vining Euonymus, which tends to be hardier than English Ivy, is good for very exposed locations. Bigleaf Wintercreeper Euonymus — Euonymus fortunei vegetus — and the Purple Winder Creeper Euonymus — E. fortunei coloratus — will climb on a surface with rootlets like ivy or trail downward over the same surface, so they can be planted either at the top or bottom of lower walls.
Among the shrubs suited for planting about 2- to 4-foot retaining walls are Contoneasters. Rockspray Cotoneaster — Cotoneaster horizontalis — has arching branches covered with glossy summer foliage that trail along the surface. Its strongest point is the crop of bright red fruit about the size of garden peas produced along the stems.
Bill Lamont is a professor and extension vegetable specialist in the department of plant science at Penn State. He can be reached at firstname.lastname@example.org.