The garden, in the Olympic Park, will celebrate centuries of British passion for gardens and collecting plants, with picnic lawns, timber seating and 120,000 plants from 250 different species arranged into four temperate regions.

Thousands of plants, grasses, herbs and flowers are already growing at Palmstead Nurseries and work is under way on the paths, drainage and seating for the London 2012 Garden before planting starts in the new year.

More than a quarter of the plants were not grown commercially in the UK and an extensive investigation was required to track down rare seeds, cuttings and bulbs.

The riverside London 2012 Garden will stretch for half a mile between the Aquatics Centre and Olympic Stadium on land that has been cleaned and cleared of railway sidings, contamination and Japanese knotweed.

Visiting the nursery with Ashford MP Damian Green, Olympic Delivery Authority chairman John Armitt said: "The 2012 Garden will help create a colourful festival atmosphere right at the entrance to the Olympic Park during and after the Games.

"The riverside garden will celebrate Britain's passion for gardens and plant collection with plants from across the world helping mark this global sporting event for generations to come.

"The 2012 Garden will also celebrate the innovation and sterling work of UK horticultural companies that are working with us to create a new world-leading park."

Green added: "This shows how British companies from all sectors will benefit from the Olympic and Paralympic Games.

"Palmstead Nurseries have been innovative and enterprising in winning this contract, and I am delighted that an Ashford firm will be helping London look at its best for the Games."