The gardens were started 62 years ago when Sir Harold planted the Centenary Border. The border was recently redesigned and replanted and is now the longest double mixed border in the country. The gardens feature a collection of over 42,000 plants set in 180 acres of rolling Hampshire countryside. They are also home to 14 National Plant Collections including the National Collection of Oaks with over 350 different types of oaks available for public view.
Hampshire County Council leader Cllr Roy Perry said: "We are very proud to have received this prestigious award. There is always something to see at the Gardens all year round. This accolade showcases the passion and care that goes into every single plant at the Sir Harold Hillier Gardens and is a credit to all the staff, volunteers, supporters - and Hampshire County Council as sole trustee."