GCA chief executive Iain Wylie said: "We're really sorry to see Liz go but completely understand her decision and wish her all the very best with her exciting, new venture. She has been a pleasure to work with.
"We've begun the task to look for a replacement for her and we're very happy to speak to people interested in the post from all areas of the industry. Anyone keen to find out more about the role should contact me via email or phone at the GCA before we start the recruitment process in earnest so we can ensure they get full details sent out to them."
Hutson, who has worked for B&Q and Fisons Horticulture, has more than 35 years working in the gardening sector.
She became a training and marketing consultant in 1990 and has since worked with numerous independent and multiple outlets.
In 1992, she wrote the Garden Care training pack, which is recognised and used throughout the industry and has run a series of industry roadshows and plans to do more of these in the future.
She said: "I have enjoyed working with the GCA team, the privilege of visiting the member centres and meeting the staff. I will miss it, but unfortunately it is just not possible to do everything one would like and there are a number of new projects I want to develop."