The Syon Abbey Herbal was written by Thomas Betson in his notebook, sometime between his profession as a priest-brother at the Bridgettine double monastery of Syon Abbey near London, and his death there in 1517. He is the last recorded Librarian at Syon, and also wrote the still extant Syon Library catalogue. The Syon Abbey Herbal is divided into two main parts – a list of healing plants from Greek, Latin, French and Middle English sources; and a list of remedies from Latin and English sources. One chapter, wholly in Latin, is on the use of urine for diagnosis, particularly of women's conditions; another is on herbal essences in distilled alcohol. The appendices include a tentative list of Linnean names for Betson's plants; A list of diseases in the manuscript; and plants at Syon House in 1548, listed by William Turner.
The Syon Abbey Herbal is a useful contribution to the study of the transition from medieval to early modern medicine. Syon had one of the best equipped late medieval medical libraries in both Britain and Europe. It contained several hundred medical and medical-astrology titles, many unique in Britain to Syon. Almost all of the 1747 volumes in Betson's library are now lost. Only two medical books have ever been found, a Gilbertus Anglicus Compendium Medicinae in English, and an astrological guide.