US Edition Count Lennart Bernadotte, who has died aged 95, was the owner of Mainau, the celebrated botanic garden on an island in Lake Constance, Germany, which every year draws some 1.7 million visitors.
Bernadotte was a grandson of King Gustaf V of Sweden, and in 1932 he had caused something of a scandal by marrying a commoner, Karin Nissvandt, against his parents' wishes and without royal consent. Under Sweden's Act of Succession, Bernadotte thereby forfeited his princely titles, as well as his chance of inheriting the throne. The pair had to travel to London to wed.
His unhappiness at his parents' disapproval was in part assuaged by his being given Mainau, which had belonged to his grandmother, Queen Viktoria, daughter of Grand Duke Friedrich I of Baden.
Situated at the western end of Lake Constance, with which Germany, Austria and Switzerland all share a border, the 111-acre island had fallen into Swedish hands during the Thirty Years' War. Later it was owned by the Teutonic Order, which built a baroque palace there.
In the mid-19th century, by which time it had passed to Baden, the Grand Duke began to take advantage of its balmy micro-climate to plant an Italianate rose garden and to start an arboretum. During the 70-year tenure of his great-grandson, Bernadotte, the work was considerably extended, so that now some 350,000 flowers bloom there every summer.
Its collection includes 6,000 types of orchid, 800 species of hyacinth and 300 varieties of rhododendron, as well as 30,000 rose trees. The island, which affords magnificent views south to the Swiss Alps, also boasts a palm house and the largest butterfly house in central Europe, as well as a quarter of a million sunflowers.
Bernadotte was at the forefront of environmentally-principled gardening, having been one of the earliest proponents of the Green movement in the 1950s. Mainau, which has close links with Kew, was the first garden in Europe to pass an eco-audit, in 1998, and every year for half a century it has played host to a gathering of Nobel laureates and students for a discussion of scientific and ecological issues.
Mainau's owner was a much admired and popular figure in Germany, where, on account of his philoprogenitive prowess (he had nine children, the youngest born 50 years after his eldest), he was nicknamed by the press "Spermadotte". He started the country's "Most Beautiful Village" contest in the 1950s, and was also president of the German Horticultural Society for 30 years from 1951. That year, too, he was ennobled once more, as Count of Wisborg, in recognition of his beautification of the "Island of Flowers".
He was born Prince Gustaf Lennart Nicolaus Paul, Duke of Småland, in the Royal Palace at Stockholm on May 8 1909. His father, Prince Wilhelm, was the second son of Gustaf V, while his mother was the Grand Duchess Maria, daughter of the Grand Duke Paul, the sixth son of Tsar Alexander II. Lennart afterwards remembered that the servants took pleasure in annoying his father by correctly addressing his wife as "Your Imperial Highness", Wilhelm meriting merely ordinary royal rank.
Lennart was an only child, for his parents divorced in 1914 and the Grand Duchess returned to Russia – only for her father to be shot by the Bolsheviks. His own upbringing was entrusted to his grandmother, Queen Viktoria, and it was conventionally strict.
When the Second World War came, Bernadotte decided to leave Germany on account of political developments, and returned to Sweden. He had always been keen on cameras, and now took up the editorship of a photographic magazine, Foto; he also co-founded a film company, Artwork, which later won an Oscar for its documentary on the voyage of the Kon-Tiki, Thor Heyerdahl's raft. In 1990 an exhibition of his photographs of Mainau held in St Petersburg would draw 1.4 million visitors.
After the war, Bernadotte organised camps for the YMCA on the island before turning his attentions once more to plantsmanship. In 1974 the Count, who was an honorary member of the Royal Horticultural Society, entrusted ownership and future care of the island to a family foundation.
The Bernadottes are famed for their longevity. The Count himself attributed his long life to the large brood he had with his second wife, Sonja Haunz, whom he married in 1972 after his marriage to Karin Bernadotte was dissolved earlier that year. His new Countess, who had formerly been his personal assistant and was 35 years his junior, is now responsible for the management of the garden.
Lennart Bernadotte died on Mainau on December 21. He is survived by a son and two daughters of his first marriage (another daughter predeceased him), and by the two sons and three daughters of the second.