“The majority of people live in cities, and they actually really like plants – just look at the collections of pots on balconies and windowsills,” says The Greenwall Company founder, Mark Paul. Once focused on residential projects on the northern beaches, this landscape designer started experimenting with tree and rock plantings 25 years ago.

With some 5,000 square metres of installations under his belt, the City of Sydney invited Paul to be part of their greenwall trials program. Completed last week, a five-year project at the Goulburn Street car park has seen the set-up of vertical gardens along the imposing ‘70s concrete façade. “It’s one of the least attractive buildings in the whole city,” says Paul, who proposed 10 options, from climbing plantings on one side of the building to rooftop car spaces dedicated entirely to trees.

Green space is an asset in urban areas – it cools heat-trapping concrete, makes buildings more energy efficient, cleans the air and offers a home for pollinators such as birds, bees and other insects. Paul has a vision to transform Sydney into a vibrant oasis. “We have to think big, think of the city as a larger ecosystem,” he says of creating a community of plants across multiple spots. In time, 50 hectares of urban green space means buildings’ porous concrete can start greening themselves as seeds transfer from one wall to the next. “That’s the bigger picture. We’re trying to green the city with lots of little tiny postcards.”

Paul explains Australia has relatively little protected state forests. “It’s a really tiny proportion of the environment, housing 28,000 species of plants,” Paul says. “Over the next 30 years, 75 per cent of plant biodiversity will be lost in plant habitats, unless they’re cultivated and used on buildings.” Meanwhile, there’s a range of plants suited to growing on cliff and rock faces. “Twenty per cent of the world’s plant species is already pre-adapted to greening cities,” says Paul, who uses drought-resistant local varieties that require minimal irrigation, such as rock orchids.

For urban dwellers, green space on your building could mean serious power savings – up to $6000 off the bill per year for every square metre of greenery on a home. Plus, all that living greenery makes us feel good. “People just have this thing about plants,” says Paul. “I think it makes us happy.”