The shortlist represented the best plants to appear at the Chelsea Flower Show in each of its ten decades. This year is the centenary of the event.
The winning bloom, which is thought to be a hybrid that occurred naturally in the Waterers’ garden, is a hardy variety capable of surviving frosts. It grows tall, with flowers that are larger than those of most other geraniums.
Mr and Mrs Waterer, who have both since died, first spotted their original plant in 1989. They noticed that the seedling had much larger leaves than its neighbours. When it bloomed, its flowers were also twice as large.
The following year, the couple found that it flowered for six months, from June to November, surviving hard frosts. They eventually took it to Adrian Bloom, a garden designer, who identified it as a new variety.
Geranium 'Rozanne’, pictured right, made its debut at the Chelsea Flower Show in 2000.
The Royal Horticultural Society’s Lindley Library holds records of all the plants to have appeared at the Chelsea Flower Show during its history.
Fiona Davison, head of libraries at the society, said: “The plants that were shortlisted reflect the changing patterns of how garden fashions have waxed and waned through the history of Chelsea.
“Right back in the first decade, rock-garden plants were dominant, and we come all the way through to geraniums in the new millennium.
“We have moved towards having smaller gardens that require less tending and flower for longer.”
More than 7,000 people voted online to select Geranium 'Rozanne’ as the Plant of the Centenary.
Shortlist from 100 years of the Chelsea Flower Show
Saxifraga “Tumbling Waters”
First Exhibited: 1920
This silvery leaved rock garden plant is topped with a froth of white flowers.
Pieris formosa variety forrestii
First Exhibited: 1924
A plant that originates from southeast Asia. The leaves are a brilliant red when new and the cream coloured flowers carry a faint scent.
Lupinus Russell Hybrids
First Exhibited: 1939
These rainbow coloured Lupins caused a sensation at Chelsea when they were first displayed and remain popular today.
First Exhibited: 1947
An evergreen species with bell shaped white flowers. It was discovered on the Japanese Island of Yakushima.
Rosa Iceberg (“Korbin”)
First Exhibited: 1961
This white Floribunda rose was bred in Germany but has become a firm favourite with gardeners from around the world.
Cornus “Eddie’s White Wonder”
First Exhibited: 1972
This small dogwood was firs raised in Canada. It produces a mass of white flowers in the spring and the leaves create brilliant autumn colours.
Erysimum “Bowles’s Mauve”
First Exhibited: 1982
This perennial wallflower is a short-lived plant that can grow nearly two and half feet in height and will last for two to three years. It has mauve flowers and long slender leaves.
Heuchera villosa “Palace Purple”
First Exhibited: 1983
this American plant has become popular for its coloured foliage, started a new trend for coloured leaves. It has bronze leaves with clusters of pink flowers being produced in the summer.
First Exhibited: 2000
This is a tall and fast growing geranium with violet blue flowers, streaked with red. It is well known as a hardy variety.
Streptocarpus “Harlequin Blue”
First Exhibited: 2010
This compact plant was the first Streptocarpus to carry two colours on it flowers. The upper petals are blue while the lower ones are yellow.
(Source The Telegraph UK)