The Garden Centre Association (GCA) is to move back in with the Horticultural Trades Association (HTA) at Theale, Reading on 1 February 2013.
Meanwhile, GIMA is to move its headquarters to the Federation of Garden and Leisure Manufacturers in Brasted, Kent, where Gardenex Petquip and CHA are based.
HTA director general Carol Paris said, "HTA and GCA have been discussing this move for some time. It is important that both organisations retain their individuality yet have the opportunity to work more closely together on issues affecting the industry. It will be much easier to do this when we are sharing offices."
GCA chairman Peter Burks added: "Both myself and Carol are committed to the various parts of our industry working together to make it stronger, more vibrant and prosperous. There is no benefit in duplicating effort and working from one office will enable us to more readily determine and address the unique needs of our members."
GIMA director Neil Gow said: "There are good synergies there and this will enable us to provide even better value for our membership."