Façade greening or vertical gardening are the current terms for a very old practice among gardeners. Vines planted at the base of a building adhere to its walls or climb a structure nearby, such as a trellis. A country cottage adorned with Virginia creeper (Parthenocissus quinquefolia) or a stately brownstone clad in Boston ivy (Parthenocissus tricuspidata) are classic examples of this type of green wall.
Once considered simply a nice ornamental touch, vines are now being recognized for their economic and environmental benefits. Studies have demonstrated that vines planted on south-facing walls can result in at least a 10-degree temperature reduction on the wall’s surface. The shade provided prevents solar heat’s absorption into the wall, resulting in reduced need for air-conditioning and decreased energy costs. The process of transpiration, whereby plants take in water and emit moisture through their leaves, further reduces heat when the moisture from the leaves evaporates into the atmosphere.
Green walls also have benefits in winter. The air gap between a vine and the exterior of a building reduce the effect of wind chill, reducing heating costs. Vines also act as a sound barrier and reduce the polluting effect of dust in the environment.
Boston ivy and Virginia creeper flourish in many climates and require no additional structural support. They can be considered nuisance vines when they climb upon woody plants or smother nearby herbaceous perennials. Some say that vines damage masonry, but sound structural walls are not damaged by their usage. Painted surfaces and stucco walls are not good candidates for vines that are self-clinging, as their roots and discs leave marks.
For homeowners who wish to try their hand at green walls, the best candidates are vines. Most of these selections require a minimum of six hours of sun per day. Clematis like their leaves in the sun but prefer a cool root zone, so perennials or shrubs planted at the base are helpful. Boston ivy and Virginia creeper will tolerate a shadier location, but their fall color will not be as brilliant in shade. Climbing hydrangea (Hydrangea anomola subsp. petiolaris) prefers part shade, but it can be slow to establish.
The following is a summary of vines and climbers suited to our Zone 5b climate:
• Boston ivy and Virginia creeper climb via disc-like projections that attach to smooth surfaces. They both are aggressive vines and will require some pruning, but they will quickly achieve the energy-saving effects of façade greening.
• Climbing hydrangea and Japanese hydrangea vine (Schizophragma hydrangeoides ‘Moonlight’) have aerial roots allowing them to climb without structural support. Japanese hydrangea will tolerate part-shade.
• Native wisterias, including Kentucky (Wisteria macrostachya) and American (W. frutescens), are better candidates than their Asian relatives. But all wisterias are vigorous and require strong structural support. They climb via twining stems that wrap themselves around a support. If you desire a green wall featuring wisteria, support it on a strong cable-like structure erected a short distance from the building itself.
• Clematis is a lovely vine that climbs by wrapping its leaf petioles onto a structure. It requires some intervention to begin its climb by wrapping or tying the vine onto a trellis or post. Vigorous clematis vines suitable for façade greening include Clematis montana, sweet autumn clematis (C. terniflora) and tougher, large-flowered cultivars such as ‘Jackmanii,’ ‘Mrs. Cholmondeley,' 'Henryii' and ‘Perle d’Azur.’
• Climbing roses require support. They produce long canes that can be tied to a structure. There are roses suitable for façade greening, but they require regular pruning. Reliable climbers in our area that are relatively pest- and disease-free include ‘Sally Holmes,‘ ’William Baffin,’ ‘Zephirine Drouhin’ (thornless) and ‘New Dawn,’ a commonly recommended rose with brutal thorns that make it tough to maintain.
• Wall shrubs and fruit trees. Apples, pears and grapes are good candidates to be trained as espaliers. Espaliered fruit trees are trained and pruned to a frame and are grown in a flat plane against a wall, usually with southern exposure. Because they take up less space than most fruit trees, espaliers are a good option for those wanting to grow fruit in a small space.
• Hardy kiwi (Actinidia arguta ‘Issai’) is a self-fertile female vine that blooms in mid-summer and produces miniature kiwi fruits after the first year of planting.
Do not plant vines invasive in our area, including porcelain-berry, akebia, bittersweet, Japanese honeysuckle, English ivy and Japanese or Chinese wisteria. For a complete list of invasive species, visit www.dcnr.state.pa.us
The green wall concept has taken root and is here to stay. In a future column, master gardeners will discuss living walls, which are modular vertical structures that contain the entire root system of the plants growing upon them. The best local example is at One PNC Plaza, Downtown. The various textures and colored foliage of plants create the PNC logo. Living walls are also being installed in interior spaces as art installations.
Other examples of vegetated surfaces include green roofs and planted retaining walls. These innovative techniques have environmental benefits, including erosion control and stormwater management.
Patricia Dandrea Kaizer is a Penn State master gardener. Columns by master gardeners sometimes appear in place of the Garden Q&A by Sandy Feather, a Penn State educator.