Backers from the horticulture industry are also behind the contest with a string of UK garden centre giants lending their assistance.
The community gardening campaign - now in its third year - is sponsored by the Horticultural Trades Association with national media partner the Sunday People.
Cultivation Street is offering £20,000 of National Garden Gift Vouchers annually in prizes, Cultivation Street has attracted thousands of entries from across the country.
This year is set to be the most successful yet, with record numbers of entries and the support of garden centre giants Dobbies, Squires, Haskins, Strikes, Notcutts, Frosts and Hillview – totalling more than 100 outlets in the UK.
Each of the centres is displaying prominent Cultivation Street signage, entry forms and offering advice and planting information alongside their usual service.
This year, Philip Turvil, Grow Wild programme manager at the Royal Botanic Gardens, Kew, will be helping to judge the Pollination Street category – a new £500 award for the best community garden aimed at wildlife.
He said: "I’m delighted to be taking part in the judging for the Cultivation Street campaign – it’s a brilliant way of encouraging community gardening at all levels across the UK.
"I’m especially happy that the Grow Wild programme is backing Pollination Street – promoting wildlife at a local level is something we can all support.
"I know there’s a huge amount of creativity and enthusiasm out there and I’m looking forward to seeing the entries."
Simon Sadinsky, education manager for The Prince’s Foundation for Building Community will judge the Sustainability & Community category for the gardening project most in tune with natural harmony and sustainability via recycling, sustainable planting and timeless skills like dry stone walling.
He said: "Green spaces play an important role in bringing communities together and creating beautiful, harmonious places. We believe that engaging communities in creating sustainable open spaces can make a huge difference both to the environment and local residents, particularly in our urban areas."
Founder David Domoney said: "The word ‘community’ is a hot topic these days. People say our communities are fractured. They even say we have become isolated.
"But I believe gardening has the power to bring people together. It’s a nurturing, uplifting pastime that forces us to step back from our busy, technology-filled lives and reconnect with nature and with each other.
"We’re all about getting people back into their gardens and community spaces, working together and pooling their talents and enthusiasm for everyone’s benefit with the support of the horticulture industry.
"So I’m delighted the industry’s getting behind Cultivation Street. To have luminaries like Kew Gardens and The Princes Foundation for Building Community on board – as well as fantastic support from the UK’s best garden centres – is just amazing!
"There’s still a lot of work to do. A Mori Poll for the RHS suggested one in four British front gardens are now paved over. Given we have around 19.1million front gardens across the country, that’s a lot of paving.
"But if, as an industry, we can continue working together to encourage a life-long love of gardening, I believe there is a lot we can do to turn this around."
Cultivation Street has already handed out £40,000 in National Garden Gift Vouchers to winners and runners-up across the UK over the past two years.
While the main category aims to promote front gardens exclusively – entrants needing a minimum of three consecutive gardens to take part – there are five regional competitions and seven other general community gardening categories on offer.
They are designed to attract the widest amount of participation from community organisations, voluntary groups, schools and ordinary gardeners.
These range from Cultivation School – for the school that has involved pupils, teachers and parents in creating gardens and fostering a lifelong love of horticulture – to Transformation Street for the most dramatic turnaround.
At every level, participants are encouraged to support their local garden centres and, in turn, Cultivation St is asking garden retailers to offer advice, information and encouragement in any way they can.HTA diretcor general Carol Paris said: "We’re very fortunate to have been able to support Cultivation Street for three years running now – it’s been a marvellous and heart-warming journey for everyone involved.
"It’s fantastic this year to see the industry rallying around a high-profile media campaign that truly brings out the best in UK horticulture and encourages people to support this vital British business that provides so many jobs and so much enjoyment for people."