The award scheme celebrates gardeners who have battled physical and psychological hardships to create community green spaces.
The Southend-on-Sea association's members turned overgrown plots in Sherbourne Gardens into a series of allotments.
Speaking at the event, TV gardener Alan Titchmarsh said: "Many people say gardening is an escape, but it's an escape to reality. There's nothing artificial about plants and growth."
He added: "It is a very important trade. We are at the sharp end of conservation, we get involved, we nurture. It is the most rewarding thing there is to do. It helps people to understand where their food comes from. There are many health benefits too."
Download a Gardening Against the Odds podcast which includes short interviews with Alan Titchmarsh, the overall winners from the Huntingdon's Disease Association, our director David Shreeve, Anna Cutherberton from the Daily Telegraph and Mary Raphaely, one of the London winners.