Adams ran the Garden Centre Association's administration and helped organise the annual conference from its Theale headquarters.
GCA chief executive Iain Wylie said the GCA committee had not yet decided what to do about a replacement and whether to broaden the role or change it.
He added that travel time for work may have been the reason behind the move.
He said the GCA would be short-handed in the short term as it rolls out online inspections for the first time and new online GROW training modules.
Wylie said Easter had been a struggle for some retailers, with centres in the north finding cold weather did not help like-for-like sales, although against budget most were happy. He added that a lack of momentum after an early Easter continued to affect sales commenting that March "doesn't sound like it has been a stormer of a month" for members.
He said centres such as Garsons and Poplars with new restaurants had seen developments "pay dividends", and that Haskins were "quite happy" with sales.