These days, we find gardens in unconventional places, from highway median dividers to old parking lots. The City of Barcelona has elevated growing plants to an art form in unlikely places, transforming newly exposed party walls into lush vertical gardens. These cascading gardens turn urban blight into urban beauty and, at the same time, support and encourage biodiversity.

Photo: Capella Garcia Arquitectura

In 1986, the Barcelona City Council launched The Party Wall Recovery Program and has, over the past 27 years, transformed 700 of the city’s party walls after demolishing adjacent buildings. Most of these walls had been beautified with artwork or the addition of windows, but in 2010, the City Council’s Institute of Urban Landscape employed “vegitecture” to bring one such unsightly wall to life.

Photo: Capella Garcia Arquitectura

The city engaged  Capella Garcia Arquitectura to design the Jardí Tarradellas (The Tarradellas Garden or the “Green Side-Wall”). This massive modular vertical garden transformed a party wall into a living wall, a free-standing green facade covering one side of a residential tower in the city’s Les Corts district, where Roman villas once stood before 20th-century urbanization.

Behind the Scenes
Though not open for public viewing, City Council representatives arranged a private guided tour for me, my Barcelona hosts, and our friends from ASESCUVE, the Spanish Association of Green Roofs. I had read about and seen photos of the impressive green facade, but the virtual view offered limited insight into the actual experience, which touched all the senses.

Standing before the soaring vertical garden, I enjoyed a complete sensory experience not just from the view but from the strong, sweet fragrance of climbing Trachelospermum jasminoides, the white star-shaped flowers cascading alongside neighboring shrubby purple Solanum jasminoides.

The towering green facade displays low-maintenance plants that change color and scent with the seasons, a true living wall whose personality evolves, transforms, and regenerates itself throughout the year.

Experimental “Vegitecture”
Extending about four feet up from the pavement, a natural stone wall serves as the garden’s foundation, stretching independently and parallel to the building’s foundation.

The landscape maintenance team pointed out various sedums and tiny succulents popping through the rock crevasses. They explained that they’d been experimenting with the green base, testing different plants to see which grew best.

Although the horticulture team had experienced some expected failures–the first sedums they planted did not root–we all agreed that what was protruding now through the stone wall seemed to be prospering.

Looking up from the ground, we could see the structure narrowing gradually as it rose to the top, about 69 feet (about 21 meters) above street level.

The freestanding structure wraps around and attaches to the side of the building. 

Stacked Balcony Garden Design
Our behind-the-scenes tour began as we climbed the green facade’s supporting skeleton, a hidden grid of prefabricated, non-corrosive galvanized steel stairs and frames that had been assembled on site.

The facade’s “balconies” were visible during construction. Photo: Capella Garcia Arquitectura. 

A contiguous network of lightweight galvanized rectangular planters forms a series of connected balconies that rise eight stories from the building’s rugged stone wall base.

Inside, we stood on expanded metal grid platforms–like scaffolding–through which we could see the floors below and above us.

Our guides demonstrated the inner workings of the garden’s drip irrigation system, operated remotely from a smartphone.

Through a network of connected tubes, the system automatically feeds the planters with programmed doses of water and fertilizer on alternate odd and even days, employing a controlled drainage system to conserve water by allowing excess water from the floor above to drip down to the one below.

Easy Planting, Easy Maintenance
Interior access to the garden distinguishes this design from other green walls whose planting and maintenance must be facilitated from the exterior, requiring elevated platforms (like window washers use), making access difficult and potentially dangerous, and increasing labor costs. At Terradellas, maintenance teams can easily reach the modular planted platforms via the interior stairway and raise materials and plants using an integrated internal pulley system.

A New Urban Ecosystem
The towering vertical garden, maintained by the city’s Department of Parks and Gardens, beautifies this once-bleak city corner between Carrer Berlín and Carrer Marquès de Sentmenat and has created a new ecosystem.

Like other living facades, this one generates oxygen and absorbs CO2, described as an enormous “lung” that filters dust, fumes, and pollution while also establishing an acoustic screen that suppresses noise. The green wall provides a 75% reduction in cooling, making it possible to reduce energy demand by 25% depending on the thickness of the plants, saving the building’s residents energy by cooling the building in summer and retaining warmth in winter.

The Tarradellas garden also provides a natural habitat for a variety of urban wildlife, including bats and eight types of birds, encouraging colonization within its structure. From the interior, we were able to view the bird and bat houses designed by renowned Catalonian green wall expert Alex Puig. (Stay tuned for the upcoming feature on my visit to Alex Puig’s Girona nursery and studio, where I participated in an impromptu sustainable design colloquium.)

Even in the generally unseen interior, we nearly overlooked little surprises and unexpected private statements, like the little inconspicuously placed bird sculptures perched here and there amid the structure’s metal grid.

As Barcelona’s Director of Green Spaces and Biodiversity, Esther Murillo, explained, Jardí Tarradellas has successfully experimented with what will and will not work effectively for future projects. Although this project has proved not cost-effective enough to reproduce, the city has learned much from it. It now has ideas and plans for the transformation of many more party walls into natural habitats that will improve the health and welfare of all of Barcelona’s living creatures.

Unless otherwise noted, all photos by Robin Plaskoff Horton for Urban Gardens. Subject to copyright.

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Note: This is the first in a series of posts about my recent visit to Barcelona and Girona, where a group of Spanish landscape designers who follow this blog invited me to meet in person and experience firsthand some of the greenest and greatest designs from Catalonia’s creative community of renown garden and floral designers, urban ecologists, and green architects. (Feel free to repost this story, but please link back to Urban Gardens as the source.) Stay tuned for much more!!