I heard through Ancestry.co.uk from Kelly and Claire Thomas, great-nieces of Sergeant Frederick Honey who worked at Kew Gardens and was killed at Arras in April 1917.

Sergeant Frederick Honey of Kew Gardens (right) with his brother Chris (left) (Family photo from Kelly and Claire Thomas family collection used with permission / via Ancestry.co.uk)
On their family tree they had this interesting photograph of Fredrick and his brother Chris in uniform.
“Fred and Chris were our great uncles. We are more than happy for you to use the photo on your blog, it is lovely for him to be remembered. Christopher was also killed at war within about 2 months of Fred.
Though we knew Fred was a gardener, we had no idea until very recently that it was at Kew Gardens and certainly no idea of the memorial. We live fairly local so it would be lovely to go and see it.”

RBG Kew’s war memorial, Temple of Arethusa, Kew (Image copyright : Kew website)
He is mentioned in a list of “Gangers, labourers and boys” in Kew’s 1914 staff list and as one of “six Members of the labouring staff killed in action” in the Kew Guild Journal 1919 Roll of Honour.
You can read more about Frederick Honey here https://worldwarzoogardener1939.wordpress.com/2017/04/17/remembering-frederick-honey-of-kew-gardens-died-ww1-17-april-1917/
and at my main WW1 Kew Gardens blogpost
A little more about Fred and Chris Honey.
Frederick (born 1889) was listed in the 1911 census as a garden labourer employed by the Board of Agriculture, a connection that may describe or lead to work at such an official workplace as Kew.
Frederick’s older brother Gunner Christopher Thomas Honey 68818, 51st Siege Battery, Royal Garrison Artillery died of wounds in Base Hospital at Boulogne on 12th June 1917, aged 32.
Born 1885, in civilian life he was in Christopher was a ‘Carman‘ or Carrier of Wines and Spirits. This may suggest a working knowledge of horses and heavy work, useful in any artillery regiment.
He was the son of Thomas & Maria Honey of 64, Alexandra Road, Richmond. Thomas was a general labourer.
Chris enlisted in Richmond and is buried in Boulogne Eastern Cemetery plot F. 102.
The Richmond War Memorial lists him as an MM Military Medal.