The 14 judges tour from 30 July until 10 August.
Judges assess horticultural achievement, community participation and environmental responsibility.
Projects to be assessed include wildlife conservation areas and public spaces such as parks and community gardens. Everything from the sustainability of a planting scheme to the cleanliness of a street bench, including how much the community engages local schools, will come under inspection.
Judging panel chair Roger Burnett said: "Our finalists have had to endure difficult weather conditions and ongoing council cuts. But this is why I'm even more excited than normal, because I love seeing the imaginative ways communities overcome challenges. It was reported that groups were pulling out of
Britain in Bloom because of these problems but, in fact, we've had a ten percent increase in the number of groups signing up, making it a record year for ‘Bloom'. Nothing fazes our volunteers and RHS Britain in Bloom 2012 represents a sense of community spirit and endeavor which is an inspiration to us all."
Each year, an estimated 200,000 volunteers contribute an average of around 44 hours per person to local Britain in Bloom activities. These volunteers - nearly three times the number involved in the Olympics - plant hundreds of thousands of trees, shrubs and plants to green-up and clean-up more than a million acres of public space.
Results will be announced on 6 October 2012 at St Peter Port, Guernsey. Finalists will be awarded RHS gold, silver-gilt, silver or bronze medals. There is also an award for best in category, as well as special discretionary awards given for achieving excellence in particular fields.
RHS Britain in Bloom national judging panel:
Roger Burnett - Chair
Jeff Bates - Deputy chair
Jon Wheatley - Deputy chair
Village, city judging team
Roger Burnett and Sharon Thomas
Large town, small village judging team
Jeff Bates and Brendan Mowforth
Urban community, coastal over 12,000 judging team
Mel Henley and Martyn Hird
Town, coastal up to 12,000 judging team
Nigel Bishop and Sue Wood
Large village, small city judging team
Jim Goodwin and Andrew Jackson
Small town, large city judging team
Rae Beckwith and Jon Wheatley
Champion of champions judging team
Jim Knight and John Woodward