At the entrance to the Urban Gardening exhibition, there is a large photograph of a middle-aged woman in Liverpool who is defiantly feeding pigeons at the front of her back-to-back terraced property. The neighbouring houses have been boarded up with metal sheets and her home is a vivid example of not giving in to the developers: it is a riot of colour thanks to the pot plants on her front step and beneath the front window.
The exhibition at Urbis, Manchester's museum of the city centre, celebrates the importance of city-centre gardens no matter how big or small the space.
Andy Brydon, the creative programmes exhibition officer, said the larger issues are the politics behind gardening and the over-reliance on oil. The exhibition begins with balconies – demonstrating that even the most compact city apartments can house gardens on balconies.
There are deliberately no Latin names given for plants as "it is more about encouraging people to start gardening, rather than giving them specialist tips" Brydon explains. The exhibition contains trendy flower boxes, made in France, housing stylish cacti and other small plants. Brydon points out that plants are essential for health and can help reduce sick building syndrome with the likes of spider plants and Boston ferns.
One plant has an eyecatching UV drip feeding it water demonstrating how plants don't have to look boring. "We were going to have urban gnomes," he adds. "But I was concerned about them getting nicked; the reason being I would have nicked them as they are that good. We also have basil growing hydroponically in the cellar along with the gnomes."
The exhibition looks at urban gardens around the world; an issue embraced in the far east. In Korea, around 80% of the population lives in apartments and they have worked to create urban gardens. Closer to home, there are spectacular urban gardens in Germany and at Canary Wharf in London in the Barclays building, where wildlife such as the black redstart have been roosting. It is a concept embraced in Manhattan, New York, and in Iceland where they have sod roofs.
A bus shelter has been brought in to Urbis and its roof has been planted with grass to show what can be achieved in an urban environment. A planter has been used as a bike stand. Behind curtains is a wormery, showing the importance of worms to maintaining ecosystems: the worms are particularly admired by small children.
Part of the exhibition is devoted to bees; charting their importance and the sheer variety in sub-species with exotic names such as the wonderfully named hairy-footed flowerbee and the cuckoo leafcutter bee. One of the controversial aspects of the exhibition is guerrilla gardening using seed bombs. Tours of Manchester will be arranged where people will be dropping seed bombs around the city. "Is this illegal?" I ask. "Probably," replies Brydon. The idea of guerrilla gardening was developed in the Lower East Side of New York in 1972 and has grown in popularity and become a direct action, quasi-political movement.
The gardens spread throughout Manhattan and up to the Bronx, until they numbered close to 1,000 in the city as a whole. But they were victims of their own success. As areas were improved so they became safer and, eventually, gentrified. Once the land underneath a garden had become attractive to build on, the garden was threatened. A series of planning battles followed in the late 1990s, and a number of gardens were bulldozed and destroyed.
Nevertheless, New York's guerrilla gardening movement has demonstrated what can be achieved. Many hundreds of gardens survive, and many have sprung up in other cities, including San Francisco and Vancouver. Essentially, guerrilla gardening makes unloved public spaces flower-filled by dropping seeds into the wasteland and allowing them to grow. Annuals such as daffodils and tulips return ever year and sunflowers can loom over dry soil.
Seed bombs are often used which are made of seeds, compost, water in a biodegradable container. Placed in empty eggs shells, they can be thrown into inaccessible places.
Less controversially, the exhibition looks at allotments and offers advice on starting an allotment. "The simple act of picking up a trowel is one of the easiest ways of increasing the value of a home and improving an area," the exhibition encourages. Having trees in a street is said to increase property values by as much as 10% - much needed in the current property market.
There is a kiosk where people can ask questions of experts in Singapore, Toronto and Melbourne, with the best question answered once a month. They can also ask questions of Richard Reynolds, who brought the concept of guerrilla gardeniing almost into the mainstream.
It is a major effort keeping the exhibition running. The beds at the entrance to the exhibition require 100 litres of water every day. "I can see why nobody has done anything like this before with living things as part of the show," Brydon jokes.
· Urban Gardening, which is free, is open at Urbis until September 7, on level 2