A unique public experiment to find out which plant makes the nation the most happy is being launched this week.
The Positive Power of Plants project, sponsored by the Horticultural Trades Association's National Garden Gift Vouchers Scheme in conjunction with TV gardening celebrity David Domoney and gardening charity Thrive, aims to raise awareness of the positive impact plants can have on people's lives.

People are being asked to name the three plants that make them happiest, by voting at www.daviddomoney.com/happy-plant-top-100. The top 100 plants will then be used to produce a top 20 list in time for the Chelsea Flower Show 2015.

David Domoney will then create a Chelsea exhibit of the shortlist - complete with state-of-the art facial recognition cameras - to monitor visitor reactions to individual plants. The experiment will reveal which of the plants creates the greatest sense of personal well-being and happiness.

The cameras will monitor eye contact, physical gestures and smiles or frowns. A giant plasma screen will display up-to-the hour analytics revealing changing patterns of interest among visitors and a running totaliser. Plants will also be ranked according to age group and gender.

Mr Domoney said his own personal favourite plants were the snowdrop, palm tree and Christmas tree.

Sir Richard Thompson, ex-president of the Royal College of Physicians, former doctor to the Queen, and patron of Thrive commented: "Just looking at a garden is scientifically proven to improve recovery time. Patients do much better after surgery if they look at 'green things' and they get out of hospital quicker.

"If everyone was encouraged to do a bit more gardening, you can well imagine how that would affect obesity rates and reduce the stress of the NHS."