Visitors to the hilltop neighborhood of Travessa do Patroc'nio in Lisbon come screeching to a halt (even if on foot) when they first glimpse a three-story house whose walls pulsate with lush vegetation. The vertical gardens of the Patroc'nio House bring a new meaning to 'picturesque,' the adjective often used to describe this city of low-rise, white- or pastel-stuccoed buildings with red-tiled roofs. In this single-family residence, two living exterior walls, angled slightly outward and supporting 4,500 plants, cause the narrow structure to look more like a tree than a townhouse. 'That's what I wanted'a tree!' exclaims the architect Lu's Rebelo de Andrade of RA\\Architecture and Design Studio in Lisbon, who completed the house with his son Tiago in 2012.

Lavender, rosemary, and saffron are only some of the fragrant flora sprouting from the effulgent walls installed by ADN Garden Design. The client, BWA'Building With Art, a developer specializing in custom residential projects, had acquired a worse-for-wear building on the tiny, 1,075-square-foot corner site. In discussing its replacement with BWA, the senior Andrade argued that the new spec house should look completely different'without being too unsettling'to attract a buyer. 'Architects have a responsibility to add to the views of others,' he explains. 'We need to be guardians of that.'