The benefits of green walls include:

• deflecting water away from the walls during heavy rain
• providing the building with an extra layer of insulation, so cutting down on energy loss and decreasing in heating requirements, even in modern, well-insulated homes
• helping to keep homes cool in summer. Unlike brick and concrete walls, green surfaces don’t store up the sun’s energy in the daytime and release it as night-time in the same way
• offering great aesthetic benefits
• providing habitats for insects
• contributing to improvement of urban air quality 
• contributing to reduced noise pollution

At their most simple, green walls can just be a planting of wall shrubs and climbers (direct greening). It’s a claddings made from plants such as pyracantha or ceanothus can provide many of the benefits offered by more complex systems.

At the other extreme are engineered, planting systems (indirect greening and living wall systems). These often consist of modules fixed against a wall that contain soil or media for the plants to grow in. These often require irrigation systems and may need professional installation and maintenance.

To be more precise, the types of green wall have been categorised as:

• Direct greening is a system where a self-attaching climber utilises the substrate of the façade for support and, sometimes, nutrition.
• Indirect greening includes some form of engineered solution, from trellises to wires for the climbers to use; thus providing a gap of insulating air between the building and the plant.
• Living wall systems (LWS), finally, are constructed with planter boxes or felt; these do not require the plants to be climbing, they often need to be irrigated and plants for intensive green roofs are frequently suitable for these systems.

This comes from Perini, K., Ottelé, M., Haas, E. M. & Raiteri, R. (2011). Greening the building envelope, façade greening and living wall systems. Open Journal of Ecology, 01, 1-8.

Decide how you wish to plant your green wall. There are various systems available, according to the size of your wall and budget.

Low cost and simple to install

• Direct greening: the simplest way of greening walls by planting climbers, wall shrubs or fruit trained as espaliers or fans

Medium cost and DIY skills required

• Indirect greening: This is within the skills of most competent DIYers and requires the surface to be first clad with wires or trellis. Climbing plants are then grown against it
• Living wall systems:  For smaller budgets, there are simple grow-bag-type products for walls or you can plant up one or more small panels that can be added to, depending on space and budget. These are available from garden centres. Introduce the plants at as small size as possible, ideally as plugs. Establishment is likely to be more successful at this stage of development

Higher cost, professional installations

• Indirect greening: Large scale installations of wire, trellis or supports, such as covering the side of a house. It is the scale that makes this more expensive and for professional installation.
• Living wall systems: can use plants grown in cells containing compost or other growing media, which are connected to drip irrigation. Harvested rainwater can be used with some systems. These are installed by specialist companies. Green walls can be installed indoors with additional artificial lighting

Choosing plants

• If the wall you are about to add plants to receives less than half a day of sun in mid-summer, choose plants for shade 
• To simplify planting and watering needs, try to choose plants that have similar light and moisture requirements to the conditions on offer

When to plant green walls

Spring is the best time to plant because plants are coming into active growth and will establish quickly.

Further reading

Planting Green Roofs and Living Walls by N Dunnett & N Kingsbury (Timber Press, 2004 ISBN-9780881929119). This book is made available through the RHS Lindley Library.

There is a broad range of plants available to clothe walls, and includes the following:

• Climbers and wall shrubs are the simplest way of adding interest to walls. There will be a climber to suit your wall, whether in sun or shade
• In green wall systems, a range of herbaceous perennials, grasses, herbs, fruit and vegetables can be planted 
• Plants for summer interest (sold as annuals, patio plants or bedding perform well and are widely available as plugs in spring. Alternatively, grow plants from seed. Experimentation with different plants is also worthwhile

Vegetables and herbs

Tolerant of shade
Alpine strawberries, chard, chives, land cress, lambs lettuce, lettuce, parsley, rocket and strawberry ‘Mara des Bois’.

Sunny positions
Strawberries: seed-raised everbearers (sometimes known as perpetual strawberries), such as ‘Aromel’ and ‘Mara des Bois’, oregano/marjoram, thyme and shade tolerant fruit and vegetables with adequate irrigation.

Summer interest for walls

Flowering bedding plants tolerant of shade 
Begonias and busy lizzies.

Bedding plants grown for their foliage
Ipomoea ‘Sweet Caroline’
Tradescantia pallida ‘Purpurea’

Plants for summer interest – sunny
Begonia ‘Million Kisses Series’, Bidens ferulifolia, busy lizzie, ivy-leaved pelargoniums, petunias and verbena.

Hardy perennials

The following plants will thrive in sun too, as long as there is a good supply of water.

Shade-tolerant perennials
Ajuga reptens, often hardy Begonia evansiana, Bergenia, Carex oshimensis ‘Evergold’, Cornus canadensis, Epimedium, ferns, Fuchsia magellanica AGM, Heuchera ‘Key Lime Pie’, Heucherella, hostas, Lamium, Liriope, Lysimachia nummularia ‘Aurea’ AGM (creeping Jenny), Pachysandra terminalis and Tiarella.

Perennials  for a sunny position
Erigeron karvinskianus AGM, Euphorbia, Festuca glauca, Helianthemum and sedums.

The following places exhibit engineered planting systems. However, most gardens open to the public display wall shrubs and climbers that can also be used.

UK

• Anthropolgie, Regent Street, London 
• The Athenaeum Hotel, London has one of the tallest green walls in Europe
• LG Arena, Birmingham
• Westfield Shopping Centre, Shepherd’s Bush London boasts one of the UK’s longest living walls

Europe

• Les Halles, Avignon
• Musée du Quai Branly, Paris
• Six Senses Spa, Paris
• Trussadi Café, Milan
• Herzog & de Meuron’s Caixa Forum, Madrid

Asia

• Tai Pai National  Theatre, Taiwan