From the Kew Guild: "The Kew Guild was founded in 1893, as an offshoot of the Kew Mutual Improvement Society (itself created in 1871), with an intention of uniting past and present “Kewites” by means of the publication of an annual journal that would convey news and facilitate communication. The Director, William Thiselton-Dyer, gave his blessing and a committee was formed to carry out the scheme, consisting of W.Watson, W.J. Bean, G.H. Krumbiegel, J. Brown, A.A. Pettigrew and J. Aikman. .... It was also during the First World War that women gardeners became eligible for membership when they took the places of the men who had gone on active service."
That page has a link to an 11 minute 1942 film about Kew Gardens.