Task: Question Generation
Input (English): Passage: Sissinghurst Castle Garden, at Sissinghurst in the Weald of Kent in England, was created by Vita Sackville-West, poet and writer, and her husband Harold Nicolson, author and diplomat. It is among the most famous gardens in England and is designated Grade I on Historic England's register of historic parks and gardens. It was bought by Sackville-West in 1930, and over the next thirty years, working with, and later succeeded by, a series of notable head gardeners, she and Nicolson transformed a farmstead of "squalor and slovenly disorder" into one of the world's most influential gardens. Following Sackville-West's death in 1962, the estate was donated to the National Trust for Places of Historic Interest or Natural Beauty. It is one of the Trust's most popular properties, with nearly 200,000 visitors in 2017.
The gardens contain an internationally respected plant collection, particularly the assemblage of old garden roses. The writer Anne Scott-James considered the roses at Sissinghurst to be "one of the finest collections in the world". A number of plants propagated in the gardens bear names related to people connected with Sissinghurst or the name of the garden itself. The garden design is based on axial walks that open onto enclosed gardens, termed "garden rooms", one of the earliest examples of this gardening style. Among the individual "garden rooms", the White Garden has been particularly influential, with the horticulturalist Tony Lord describing it as "the most ambitious ... of its time, the most entrancing of its type."The site of Sissinghurst is ancient and has been occupied since at least the Middle Ages. The present-day buildings began as a house built in the 1530s by Sir John Baker. In 1554 Sir John's daughter Cecily married Thomas Sackville, 1st Earl of Dorset, an ancestor of Vita Sackville-West. By the 18th century the Baker's fortunes had waned, and the house, renamed Sissinghurst Castle, was leased to the government to act as a prisoner-of-war camp during the Seven Years' War. The prisoners caused great damage and by the 19th century much of Sir Richard's house had been demolished. In the mid-19th century, the remaining buildings were in use as a workhouse, and by the 20th century Sissinghurst had declined to the status of a farmstead. In 1928 the castle was advertised for sale but remained unsold for two years.
Output (English): What is the name of the castle that was for sale for two years?