Urban gardener, Cleve West: Here's one I made earlier

I often wonder whether gardens quietly shudder every time there is talk of moving house. I wouldn't be surprised. Gardens are more likely to undergo anything from a simple nip and tuck to a full-scale revamp just before, or just after change of ownership. A casual "let's move to the country" will have earth worms burrowing for their lives, ladybirds flying away from home and plants eyeing each other nervously wondering who's for the chop.

There is no doubt that a well-kept garden can add value to your property (some estate agents say up to 20 per cent) and it's a useful sales pitch for us garden designers trying to get clients to spend up to 10 per cent of the property's value on landscaping. But while I think that a well-designed garden will, in most cases, help clinch a deal, much depends on who the garden was designed for in the first place. Our backyard, for instance, with a 60cm-deep pond spanning the width of the garden, is hardly likely to appeal to couples with young children, the very elderly or those with some disabilities - a sizeable chunk of the buyers' market. The garden was designed and built to suit my partner and I, with no real concern about how it might affect the property's saleability.

A good garden is always going to be an asset, and the idea that gardens (especially small town gardens) can be changed as easily as a kitchen or bathroom is a reality. Many house-owners looking to inch their way up the property ladder are seeing the value in spending money on the "outdoor room". Unlike kitchens and bathrooms, however, gardens pose a distinct challenge, not just because there are so many variables but also because they are alive and constantly changing. Passionate gardeners know this and, on buying a property, are often prepared to let the garden run its course for at least a year, noting what comes up each season, before committing to any wholesale changes.

Designers generally prefer those who plan to stay put for at least five years so they can see their creation evolve in to something that resembles maturity. Five years, however, is nothing on the horticultural calendar and while the quick turn around of house buying and selling helps to fuel the garden design industry, many designers look for clients who have a real interest in keeping the garden going long after contractors have shovelled away the last few bags of ballast.

If you are selling a house, a simple tidy might be all that's needed. Try to resist imposing a cheap makeover as bad design sticks out a mile and won't necessarily add anything to the property's value. On the other hand, if you've just bought a house and are keen to make changes, try to resist the urge to get a head-start by doing an initial clearance before you have a good idea what you want to do. Opportunities are often missed by taking out something that, with some careful thought or pruning, could have been a major asset to the garden. Ivy is the most likely plant to get the chop in both scenarios, but the ubiquitous evergreen can lend a real sense of maturity to a space. Admittedly it can get way above its station from time to time, but sensitive reining in is far better than slash and burn - and realising later on that what that wall or fence actually needs is some greenery to make the space feel more like a garden and less like a prison courtyard. The other mistake is to tack on a miserly strip of trellis to your boundary in the belief that it will provide some privacy - it will do nothing more than draw attention to the part of the garden that you are trying to ignore.

I encountered a situation recently where both the ivy massacre and trellis abhorrence (on top of a beautiful old wall) had taken place just before the new house-owners decided to call me round. I bit my lip for a while but eventually had to risk losing the job by pointing out that getting rid of the trellis and letting some of the ivy grow up the walls would help the garden to restore a bit of dignity. The owners are still speaking to me … for now at least. For a nationwide list of accredited designers, visit www.sgd.org.uk