Fisher Tomlin said people with larger gardens needed more advice if we were to slow the alarming trend for selling off part or all of the land for development.
He said while there was plenty of focus on small-garden design and landscaping there was a growing need to support large garden owners. Many owners were coming up for retirement and wanted to know how to look after the garden.
"Increasingly we are finding clients are daunted by the prospect of keeping up large gardens," he said. "Eventually some of them start thinking of selling off part of the garden to developers leading to the loss of a great natural asset."
"There are some great organisations like Thrive helping people carry on gardening but more advice on low maintenance ideas would help enormously," said Fisher Tomlin who has drawn up five top tips for reducing the maintenance and cost of a large garden.
They include cutting out weekly lawn cutting by establishing longer grass areas, flower plugs and bulbs to encourage wildlife, turning over neglected areas of the garden to orchard trees and sharing gardens with young people who don’t have their own garden.
The other two tips include introducing more shrubs into borders to reduce maintenance and using water-wise methods of planting such as dense cover to retain moisture in the ground and cut down the need for irrigation.