Refurbishment works are to be carried out at the Arboricultural Association's new home - the Malthouse at Standish - before the body moves.
The three-storey building was previously used by Gloucestershire County Council's Rural Estates team.
The £440,000 purchase came as a result of the dip in property prices.
Chairman of the Trustees Jim Quaife said: "For as long as I can remember, the Arboricultural Association has sought to own its own premises.
"The current depression in commercial property values means we have been able to secure not only an ideal base for the future but also what will become a valuable and appreciating long-term asset. This is one of the most important events in the history of the Arboricultural Association and the opportunities before us are truly exciting."