Inheriting the 1,500-acre Sandling estate in Kent from his father, he acquired a tremendous depth of knowledge of trees and shrubs, especially the rhododendrons that thrived in the 27-acre woodland garden developed by his grandfather, Laurence Hardy, from the turn of the century.
He was a true fanatic about both species rhododendrons and hybrids, some of which he bred himself. His flowers won many awards despite the fact that Sandling, exposed as it is above the cliffs near Folkestone, is one of the coldest and windiest spots in south-east England and as such not easy to garden. From the age of 30 he was invited to sit on many of the Royal Horticultural Society's committees and became a leading figure in the rhododendron world, acting as a judge at shows. He was the founder chairman of the Kent Garden Trust and in 1993 was awarded the RHS's coveted Victoria Medal of Honour, which can be held at any one time by only 63 people - the number of years that Queen Victoria reigned.
But his interests were by no means confined to the one plant: he loved gardening in all its variety. A lifelong love of daffodils was sparked when, as a boy of seven, he was given his first bulb by Lionel Richardson, the renowned Irish breeder. Hardy would eventually become a breeder himself and a respected authority on the flower, always ready to lavish praise and sound advice on this and all aspects of gardening.
His principal occupation was running the estate and its farm: his pedigree cattle and sheep, like his flowers, often won prizes. Aware from an early age that he was destined to take over the estate, he prepared himself in typically thorough fashion. After joining the Coldstream Guards towards the end of the Second World War, he worked briefly on a dairy farm, then gained qualifications in agriculture and animal husbandry at the Royal Agricultural College in Cirencester.
Soon afterwards he lost a lung through tuberculosis. This setback meant, among other things, that he was never able to go on plant- hunting trips to distant parts of the world, although he always felt that he was with the collectors in spirit and could scarcely wait for their return to inspect and discuss what they had found.
His never lost his enthusiasm and courage - qualities he needed in abundance in 1987 when the October hurricane felled more than 800 trees in the woodland garden, destroying the canopy that shielded the under-story of acid-loving shrubs. It seemed at first that all the family's work in building the garden over 90 years had been wiped out overnight, but he and his wife Carolyn, whom he married in 1953, were determined to clear the mess and restore the plantings.
The fallen timber had to be manhandled out of the garden and the resulting bonfire continued day and night for two and a half years. Today the garden is well on the way to restoration, partly through the great generosity of friends in donating new trees and shrubs, in the true spirit of gardening camaraderie that Hardy so valued and exemplified.
Carolyn Hardy, too, is well known in the world of horticulture and is a vice-president and former chairman of the National Gardens Scheme: Sandling was one of the original gardens opened to visitors for charity when the scheme was launched in 1927. The couple made a splendid team in all aspects of their lives. They had two daughters, and Hardy was gratified that both have followed in their parents' footsteps, one managing the estate farm with her husband, the other working in Sandling's walled garden.
He had an engaging, teasing sense of humour. Among his fellow enthusiasts he would introduce himself as "the gardener from Siberia" - a reference to the notorious weather conditions at Sandling. But he would never have considered leaving it. The estate was the focus of his life's activities and achievements, and he loved it with an enduring intensity.
Gerald Alan Hardy, plantsman: born Sandling, Kent 4 April 1926; married 1953 Carolyn Evanson (two daughters); died 4 February 1999.