Plants for Green
Walls
 Green walls are places where plants are growing on the sides of buildings
or other vertical structures. This may include exterior building walls,
fences or retaining walls, or even the interiors of buildings. The benefits
to planting a green wall are many, including:
- Visually enhances unappealing wall spaces.
- Cools the sides
of a building from direct summer sunlight, reducing indoor cooling
needs.
- Provides
an extra layer of insulation for building sides.
- Reduces traffic and other
urban noises from building interiors.
- Reduces the urban heat island affect
in cities.
- Improves carbon sequestration and air quality in urban
areas.
- Provides additional wildlife habitat in urban areas.
- Provides
additional points for L.E.E.D. certified buildings (Leadership in Energy
and Environmental Design Green
Building Rating System™).
- Provides additional green space in a vertical
format.
Vines, such as English ivy, creeping fig, or Virginia creeper, have
been used to enhance building facades on brick structures for many centuries.
These types of vines form adventitious roots or disks along the climbing
stem that adhere to brick and wood. These roots can penetrate small spaces
between brick mortar and cause damage to brick and wood. Successfully
removing these vines from building sides can be a costly and labor intensive
process.
Trellis or wire
There are many other methods of creating green walls other than the traditional
use of vines, including some new technological advances. The simplest
and least expensive method to create a green wall would be to construct
a freestanding or attached trellis. A freestanding trellis is a frame
of wood or metal that is anchored to the ground. Maintain a distance
from the wall of at least 6 to 8 inches to allow for air circulation
to reduce mold and moisture buildup on building sides.
Some freestanding
structures around buildings (such as fences) require building permits
or may need to meet other local ordinance codes. Vines that use
non-attaching tendrils to climb, such as coral honeysuckle (Lonicera
sempervirens), clematis (Clematis spp.), or yellow jasmine
(Gelsemium sempervirens) will use the trellis for support. Plant
species may be chosen according to the height of the wall being covered,
with some species reaching over 70 feet in height. For more species
of vines suitable for the Southeast, see the Designing
with Vines factsheet.
Wood lattice that is often available in hardware stores often has a
short use life and requires regular maintenance.
An alternative inexpensive method to a trellis is using cables or coated
wire. Similar to using string or wire for string beans, cables are anchored
into the ground and are attached to roof eaves or wall anchors. Vines
are planted in the ground and allowed to climb the wire, or may be established
in planters in the base. Vines that are planted in the ground offer the
least maintenance for watering and care as compared to other green wall
systems. The wires are spaced according to the density of foliage that
is desired. Wall anchor and wire kits are available from a variety of
manufacturers.
Green Walls
Green walls utilize a metal framework that is detached from the building
sides (similar to a freestanding trellis) and supports panel-type planting
units that hold a lightweight soil. Metal frames that are attached
to building sides will require a waterproof membrane between the growing
media and the wall surface. The panels are modular units that fit into
the metal framework, and are available in various patterns and grid
sizes. The soil media is a sponge-like sheet that holds water yet drains
freely. Plants are planted into the soil on the side of the vertical
structure. Very low growing plants (under a foot in height) are used,
including groundcovers, ferns, perennial flowers, small shrubs, and
even edible herbs. Plant species may be chosen for shade or sun locations,
and tropical species can be used for indoor green wall applications.
Indoor green walls assist in the cleansing of indoor air quality by
removing volatile organic compounds that come from paints, adhesives,
caulking, and carpeting. Supplemental irrigation is required for green
walls, and utilizes a drip system on the top wall portion which filters
down through the individual wall panels. Permeable gravel strips are
often used at the base of green walls to collect excess water and which
is used to recycle via a pump.
Vertical Gardens
Vertical gardens differ from green walls as they do not use a soil
media for the plants, but instead use a felt fabric. Similar to a
green wall, vertical gardens use a metal frame that attaches to the
building sides or may be freestanding. A thin rigid plastic sheet is
attached to the metal frame to provide stability and to provide waterproofing
to the building wall. A corrosion-resistant felt layer is attached
to the plastic sheeting to provide water and as a base to anchor the
plant roots that attach directly to the felt layer. Ferns, mosses,
sedums, and many epiphytes such as orchids and bromeliads will attach
to the felt layer. As with a green wall, the felt is irrigated from
the top with supplemental water which gravitates to the base.
Plants that would be suitable for green walls in the Southeastern U.S.
include:
Perennial wildflowers
Blanket pinwheel daisy (Gaillardia pulchella)
Painted daisy (Tanacetum coccineum)
Blazing star (Liatris spicata)
Blue-eyed grass (Sisyrinchium atlanticum)
Coreopsis (Coreopsis grandiflora)
Red salvia (Salvia coccinea)
Purple coneflower (Echinacea purpurea)
Red yucca (Hesperaloe parviflora)
Autumn sage (Salvia greggii)
Clover (Clover spp.)
Ferns
Christmas fern (Polystichum acrostichoides)
Southern beech fern (Phegopteris hexagonoptera)
Autumn fern (Dryopteris erythrosora)
Southern maidenhair (Adiantum capillus-veneris)
Ebony spleenwort (Asplenium platyneuron)
Wood fern (Thelypteris kunthii)
Vines
Coral honeysuckle (Lonicera sempervirens)
Confederate jasmine (Trachelospermum jasminoides)
Crossvine (Bignonia capreolata)
Smilax (Smilax spp.)
Trumpet creeper (Campsis radicans)
Yellow jasmine (Gelsemium sempervirens)
Virginia creeper (Parthenocissus virginicus)
Morning glory (Ipomoea spp.)
Grasses
Muhly grass (Muhlenbergia capillaries)
Sideoats grama (Bouteloua curtipendula)
Buffalo grass (Bouteloua dactyloides)
Little bluestem (Schizachyrium scoparium)
For more information on green walls, visit the following
public Web sites:
Living
Roof
Building
Design and Construction
National
Research Council Canada
Written by Robert
F. Brzuszek, Assistant Extension Professor, The Department
of Landscape Architecture, Mississippi State University.
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