Urban gardeners are used to having tight scraps of land to work with. A steep railway cutting: stained planks of wood supporting truncated terraces, plastic bottles and shiny CDs flapping around over netting and mesh. I love the mess of allotments, though ideally when they have shoots of spring green about them.

Allotments say something about communal toil, soil under the fingernails and that flavour so reminiscent of childhood for me, raw purple sprouting, which my two-year-old is just developing a taste for. Could they also play a part in a more strategic development of towns and cities?

At the Building Centre in London a new exhibition, London Yields (www.buildingcentre.co.uk to 30 May), examines at how architects can take a professional role in urban agriculture with local authorities which are starting to consider the issue. It shows how Bohn & Viljoen Architects mapped opportunities in Middlesbrough as part of its sustainable future vision and how it advocates continuous productive urban landscapes as part of a green grid of infrastructure that could one day take its place alongside essential roads and sewers. AOC has set out strategies for greening Croydon’s office rooftops. The tangible results with most of these schemes are modest so far: Croydon has one car park rooftop for vegetables now.

The pressure on land is critical. While London Mayor Boris Johnson has leant his voice to the Capital Growth Campaign for 2,012 more food-growing spaces by 2012 the Olympic developments have resulted in the clearance of long established allotments in the Lea Valley. But the arguments stack up. Urban gardening is on message with political thinking in so many ways: healthy eating, low level exercise, community cohesion cutting carbon food miles, food security (think of Cuba’s gardening answer to America sanctions). And relatively cheap seed funding can achieve a lot thanks to people willingly putting in their own time for what they perceive as their own enterprise.

Greening the increasingly dense city, cramming carrots in cuttings, rhubarb on roofs and spinach in spaces left over after planning could perhaps make it more enjoyable for us all.