Landscape architect and garden designer Annabel Downs was set to take over the reins from Peter Thomas during an SGD council meeting due to take place on Wednesday (14 January).
Downs said: "It is something I am really looking forward to doing.
"It is going to be a year of consolidation - we have had so many ideas and activities happening in the past few years I want to consolidate everything."
Former chairman Thomas said he was delighted for Downs, but would not continue as a member of the SGD council because of time constraints. "I have resigned from the council as well as being chairman," said Thomas.
"I thought if I stayed on the council I would end up doing an enormous amount of work anyway and I hope to focus on my business."
Thomas said the amount of work required for the role had led him to suggest the SGD employ a paid chief executive. "I wanted someone to be employed as a chief executive who was being paid as it is a very full job," he added. "I didn't feel it was reasonable to expect people to do it as a volunteer."
Downs said she didn't agree: "It makes a big difference having someone who is a professional career person rather than someone with the interests of the organisation at heart."