The £3.5 million proposal, which could see a 22,000 ft sq extension added to the existing 19,000 ft sq head office building, has been submitted to Midlothian Council for planning permission.

Backed by new owners Tesco, the extension would increase staff capacity from the current 100 head office employees to 300.

Extra capacity

The building will also house a staff gym and breakout areas with coffee bars

Stuart Wright, director of property at Dobbies, said: "Dobbies has a long horticultural heritage and is committed to staying at the forefront of garden centre retailing.

"As our business grows and develops we need to create extra capacity at our Midlothian head office, where we have been based for nearly 100 years.

"We will be working closely with the council on the plans in order to obtain permission for the application."

More stores

Dobbies is exploring a number of eco features for the extension.

These include the installation of a biomass boiler, which could eventually provide heat for the whole of the Melville site, a grey water system and the use of renewable timber in the construction to create a natural look and feel to the building.

The company, which was founded in 1865, now operates 24 stores across Scotland and England.

The company plans to open three more stores in 2009.