What are the main disadvantages of gardening next to a main road

A. One of the principal effects is to actually enrich the soil with nitrogen, which is a direct bi-product of exhaust fumes. The problem with the extra fertility is that it often encourages strong growing weeds like nettles and coarse grasses that can swamp more desirable flowers.

Then there are elements like lead and salt from winter road gritting that can decimate more tender plants and the sooty dust that settles on leaves, preventing plants breath properly and hindering the absorption of light.

A. Just think of driving through France and you'll visualise lines of plain trees. However, splendid and pollution-tolerant though they are, these are generally too tall for a standard British garden. There is plenty of other choice, and it basically comes down to whether you want your traffic insulation to be evergreen or deciduous.

Excellent evergreen's that will grow relatively quickly and soon filter noise are clump-forming bamboos such as Phyllostachys aurea and Phyll. bissettii, the laurels Prunus laurocerasus 'Rotundifolia', (cherry laurel) and P. lustinica (Portuguese laurel) and Hollies. It is worth considering cypresses as well for their thick evergreen foliage. The much-hated Leylandii is at its most useful screening off motorways and trunk roads, but only ever plant it if you are prepared to trim it back hard every year without fail.

A. One of the great joys of spring are the Magnolias in all shapes and forms that thrive in the atmosphere in some of our most built up and congested cities. Shrubs like Fatsia Japonica, Hydrangea macrophylla and Lilac have all also proved to be pollution tolerant.

Just a quick look at some of Britain's roadside verges provides plenty of clues as to flowering perennials that don't mind being near roads. Primroses and Cranesbills (geraniums) are all to be seen by motorways and on traffic islands, as are Poppies and Valerian, both red and white.