The archive consists of two volumes relating to work carried out at Gravetye Manor, 227 letters written to William Robinson and his nurse, Mary Gilpin, and a small number of papers collected by William Robinson. The letters reflect Robinson's wide network of friends and acquaintances, and topics represent many aspects of 19th- and early 20th-century society. His correspondents include fellow horticulturalists (E.A. Bowles, Gertrude Jekyll, Frank Crisp, Mrs C.W. Earle, Frances Wolseley, Arthur Bulley, Samuel Reynolds Hole, Robert Marnock, Ellen Willmott, Augustine Henry), botanists (J.D. Hooker, Reginald Farrer, Frederick Hanbury, Arthur Hill, J.T. Boswell, George Maw, Henry Vilmorin), scientists (Charles Darwin, Richard Owen, Oliver Lodge), social reformers (Edwin Chadwick, John Hanham), figures from the art world (Edward Burne-Jones, Frank Miles, John Ruskin, Carolus-Duran, Alfred Parsons), writers and poets (Oliver Wendell Holmes, Francis Newman, Henry Avray Tipping, E.V. Lucas, Alfred Austin, Charles Reade) and other well-known individuals such as Joseph Chamberlain, Viscount Esher, Lord Ronald Gower, Lady Constance Lytton, Heinrich Schliemann, Émile Faguet, William Tegetmeier and Vernon Lushington. While much of the correspondence focuses on gardening and horticultural matters, the letters also reflect Robinson's interest in the promotion of cremation, his protests against new taxes and the Government of the day, and include descriptions of individuals' experiences during the Franco-Prussian War and the First World War, and visits to Gravetye Manor, East Grinstead, where Robinson lived from 1883.
Correspondence relating to Robinson's life was added as an associated archive (WRO/Z1) in 2018. These papers were found with the original archive in 2013 but were not catalogued at the same time. The provenance of the papers is unknown.