John Armitt, who visited with Ashford MP Damian Green, said the 2012 Garden, stocked by Palmstead Nurseries, would help create a colourful festival atmosphere at the park entrance.
"The riverside garden will celebrate Britain’s passion for gardens and collections with specimens from across the world helping mark this 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."
Palmstead nursery is growing 60,000 plants from around the world for the 2012 Garden. The half-a-mile park will celebrate centuries of British passion for gardens.
It will include picnic lawns, timber seating and 120,000 plants from 250 different species across the world arranged into four temperate regions.
Green, who is immigration minister, said: "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"