Most houses could be spruced up with a bit of greenery but some architects have begun to embed living trees within the structure of their buildings. Jonathan Glancey branches out

Vo Trong Nghia was born in 1976, a year after the Vietnam war ended. During that 19-year conflict, napalm bombs dropped by United States aircraft petrified great tracts of forest around Phú Thùy, his hometown. Some of the remaining trees fell victim to Vo Trong’s poverty: he earned money by selling them for timber.

“You have to survive,” he says, but he felt guilty: “that’s why I need to plant again.” His yearning for absolution is reflected in his remarkable yet simple architecture, which has reintroduced nature to Ho Chi Minh City. Here, just 0.25% of the urban fabric comprises green space (compared with 27% in New York). Vo Trong’s Tree House (below), a modest, low-cost and readily reproducible residential project, is shoehorned between run-of-the-mill modern buildings in Tan Binh, one of the most densely populated districts of the city.

Laying down roots Vo Trong’s Tree House MAIN IMAGE b.e.architecture’s house built around a gum tree in Vaucluse, Sydney

The house is made up of five concrete boxes – small pavilions – clustered around a courtyard and screened off by sliding glass doors. When these are open, rooms and courtyard become one. Discreet bridges connect the bathroom and bedrooms on the upper floor. The concrete boxes double up as planters, each nurturing a local weeping-fig tree. As the trees’ foliage spreads, it forms a green canopy over the courtyard, creating a shaded, temperate space usable all year and abounding in greenery and birdsong.

“The Tree House”, says Vo Trong, “is a device to connect people to nature. It is a miniature park, and if we can build lots of houses like this, then we can make the whole city a big park.” With the commissioning of an entire Tree House-style housing estate by the Phuc Khang Corporation, a property-development company, as well as a Tree House-style student hostel for FPT University, Vo Trong is attempting to transform Ho Chi Minh City. He may well have hit upon a way of greening crowded cities worldwide.

Growing trees inside buildings might seem whimsical, but in a way branches and bricks fit comfortably together, for trees have formed the essence of at least two of the greatest approaches to architecture: Classical and Gothic. The tree trunks that supported the earliest buildings were refined into the marble columns of Greek and Roman temples, while Gothic cathedrals celebrated their close relationship with woodland both in their glade-like naves and their elaborate stone vaults, which resemble the intertwined branches of trees.

In Modernism notions of abstract geometry replaced nature as the prime source of inspiration, yet architects working in a strictly modern idiom have managed to include trees within crisp, linear designs. Stefano Boeri has completed two “Vertical Forest” residential towers (below) in Milan’s Porta Nuova Isola district. Apartments here are rather like tree houses, but with all mod cons and views across one of Europe’s great industrial townscapes.

House plants Stefano Boeri's “Vertical Forest”

The concrete balconies of Milan’s Bosco Verticale have been reinforced to bear the weight of considerable vegetation, and wind-tunnel tests have been carried out to ensure high-rise trees planted on these will remain upright in unforgiving storms. But there is no great secret to, or difficulty in, building in the company of trees. Planting in pots restricts the growth of the trees, although they will need pruning. The planters are lined with waterproof membranes and polypropylene grids designed to keep errant roots away from walls and damp at bay.

Boeri has chosen a wide variety of slow-growing deciduous trees. These include cherry, Persian ironwood and holm oak, with maple and beech, which require less sunlight, on the north sides of the towers. The advantage of these – aesthetics aside – is that during winter they allow sunlight and a degree of natural warmth to enter the apartments, while in summer their dense foliage will keep homes cooler than they would otherwise be. Boeri believes that air-conditioning ought to be necessary only on the hottest days. The trees will also help soak up odours and pollutants, filter particulates from car exhausts, muffle unwanted sounds and, for those sitting on their balconies, go some way to reducing exposure to harmful ultra-violet rays.

There will always be those who will find buildings decked out in trees a kind of betrayal of pure architectural forms. But natural curves can be used to counterpoint sharp modernism. In the Sydney suburb of Vaucluse, b.e.architecture, led by Broderick Ely, have incorporated a mature lemon-scented gum tree into a renovated modern house overlooking Sydney Harbour. The tree is the dominant feature of the house, animating its strict geometry, creating a delightful indoor-outdoor dining room and spreading its canopy over rooms on the upper floor. Neither client nor architect saw the tree as an obstacle. Instead, they conceived a creative and harmonious relationship between trees and architecture.

There is, then, both precedent and a particular logic in combining trees and buildings. And, unlike so many current proposals for sustainable architecture, intelligent buildings such as these are both peaceful and genuinely green.