Green walls can bring plant colour, seasonal interest and wildlife benefit to places where conventional gardening is impossible.  This wall garden on rue de la Verrerie covers a windowless shop front, over an entrance where lorries back in to a loading bay.

green wall bhv2        green wall bhv3

The first green wall of this type that I encountered was the front face of Avignon’s box-like, modern market hall.  It must have been an ugly building before Patrick Blanc, the French botanist who claims to have invented green walls, (murs végétaux or murs végétalisés in French) was given the task of transforming it.  The Mur Végétal des Halles, installed in 2005, faces onto an open square so the ‘wow’ factor isn’t wasted.  The wall is a spectacular abstract landscape, painted in plants and plenty of people stop to admire it.

Patrick Blanc’s first green wall was installed at the Paris Cité des Sciences et de l’Industrie in 1986.  It seems to have taken a while for the idea to catch on as, after a number of indoor installations, Blanc’s first major outdoor green wall wasn’t unveiled until 2005 on the facade of the Musée des Arts Premiers at Quai Branly.  As the photos on Patrick Blanc’s own website.   show, it’s another spectacular success,

Many other green walls have followed over the last decade, in Paris and elsewhere, and many other designers now offer similar end products with differences of technique.  The BHV wall, shown above, is a Patrick Blanc original, installed in 2007.    It’s interesting for a gardener to see what’s growing up there – ornamental sages seem to be doing particularly well – but the thriving, bushy plants have obscured any pattern in the planting design.   I guess it’s good for bees.

montorgeuil wall south         montorgeuil wall north

These two small green walls facing east and west, either side of the entrance to a primary school in rue Tiquetonne, are down at a level where you can look at the detail.  (Click on any of the small pictures on this page for a larger image).  Early in the year there were some bald patches where the plastic support structure showed through but now the plants which are doing well have spread to cover the gaps.  Erigeron karvinskianus, a rather wiry daisy from Central America which is now naturalised in parts of Europe, is thriving on both east and west walls.  It’s a natural wall plant and self seeds readily into cracks in stonework.  A bronze Heuchera is looking good on the east facing wall.  That’s another plant that seems to grow best when self-sown in unlikely places.

At their best, green walls are extraordinary works of horticultural art, with a range of environmental benefits.  The citizens of Paris clearly like them.   A proposal to install more green walls around the city was one of the projects which received most votes in the city’s 2014-15 budget participatif – when local residents get to set the priorities for a variety of environmental improvements and social activities.

creeper 3

In some locations I find it hard to see what a high-tec green wall would add to the benefits self-clinging climbing plants provide.  Climbers such as Virginia creeper (above) or climbing hydrangea offer much the same insulation benefits as a constructed green wall, provide nesting places for birds and nectar for bees.  If there’s earth for them to root in they can tap in to reserves of rain water and soil minerals, rather than being dependant on complicated watering systems with liquid nutrients.

That’s the crucial point.  If there’s a place to plant a well chosen climber with its roots in good earth, it’s a cheap and easy (if slow) route to a green wall.  If not, in those places where there’s no earth left, a mur végétalisé may be the way to go, if you can afford it.  With installation costs of anything from €500 to €2,000 per square meter and maintenance costs to match, green walls aren’t a cheap option.  But if they make people stop and look and vote for more funding for plants in the city, that must be a good thing.