The idea of vertical gardening, aka Living Walls, has been around for some years but is now emerging as clear niche that has some interesting potential. It might be a way to counter local poor air quality, it can reduce summer air temperatures and noise pollution, it can aid biodiversity and can improve health and wellbeing. On the outsides of buildings, these walls are also effective for cooling in summer and insulation in winter.

The UK’s Hadlow College, alongside University of Greenwich, has been part of an EU Erasmus+ ’Vertical Plant Life’ project to develop a curriculum for this form of gardening, details of which can be viewed here: Vertical Plant Life As part of this, Hadlow has recently installed outdoor and indoor living walls.

The first systems were constructed in the mid-1980s in Paris by Patrick Blanc. Today, there are hundreds across the globe. A breakthrough came in around 2005 when the link was made to clean air, with a realisation that living walls could remove a lot of air pollutants, particularly useful for countering so-called sick building syndrome.

On the one hand, a downside of this form of planting seems to be cost and complexity. Niall McEvoy, Business Development Manager at Scotscape Landscaping, which partnered Hadlow for its walls, cites a cost of around £400-£500 per square metre. Hadlow’s own relatively modest outdoor wall would come in at around £6500.

There is the structure itself but also the pumping mechanism to ensure a balanced supply of plant feed and water. Part of the complexity for larger walls comes from the need to provide more water to the higher parts of the wall, where there is more wind and sunlight, than lower parts. Indeed, despite the increasing use of recycled materials within the structures, there does look to be a non-green aspect to the walls.

Maintenance, particularly for large walls that cannot be reached with scaffolding or a cherry-picker, can be cumbersome. It is easy to prune and replace plants at ground level, rather harder at the top of a three storey building (where abseiling might be most appropriate). There is even now a company that specialises in financing for living walls and roofs – Green Infrastructure Leasing. And when a living wall goes wrong, it can go horribly wrong, as one or two examples have showed. The density of planting means they can be susceptible to diseases and the planting, watering and ongoing commitment to maintain them can be challenging.

On the other hand, it is perfectly feasible to have cheap and cheerful versions at home, which can be constructed, fed and maintained from ground level or on a ladder. A company such as Scotscape will provide purely the equipment, if required, but it is also feasible to build your own from readily available items from a garden or DIY centre.

The largest are typically done by corporates, in part because it helps to tick boxes related to the Building Research Establishment Environmental Assessment Method (BREEAM), the world’s longest established method of assessing, rating, and certifying the sustainability of buildings.

For instance, M&S has around 20 living walls including on its store in Sevenoaks. Others in the UK include Digby Road Apartments in London, Veolia’s facility in Leeds, and Birmingham New Street station, while there are also projects aimed at a wider uptake, such as the Paris-based Des Jardins sur les murs

The walls can help to form the wildlife corridors that are now known to be so important for species to use, they can have an edible focus, they can incorporate bug hotels and bird and bat boxes, and they might even be able to generate electricity – a study is underway in Cambridge to investigate this (all plants produce electrons when the organic matter that they excrete into the soil is broken down by bacteria).

Among plants recommended are borage, marigolds, members of the sage family, chives, lavender, and salvias. The planting will vary across the wall, will be dependent on the location, and also on the focus – such as plants that are particularly good at removing air pollutants or supporting pollinators.

‘Don’t put a thug next to a whimp,’ advises Shelley Mosco, from University of Greenwich. In others words, don’t put a slow growing plant that needs plenty of sunlight next to a fast growing one that will cause lots of shade. She emphasises that the plant list has changed a lot in recent years due to the lessons from early projects.

One good thing about the increasing maturity of the sector is that there is plenty of reading material now available. The new curriculum, covering installation, plants and maintenance, is available and is likely to be the stepping stone to the emergence of courses or modules within wider study programmes. Living walls are not for everyone and everywhere but they are likely to be a part of future urban planning, bringing plenty of benefits even within the highest density areas.