She will be retiring in January after the GCA Conference at the Crowne Plaza in Oxfordshire. Westwood has organised 13 conferences which have been a highlight of the garden retail calendar.
GCA chairman Dennis Espley said:
"Gillie will be greatly missed by all of us, and during my term I have found her great to work with, cheerfully and efficiently handling all the day to day activities of the Association. We all wish her well in a well deserved retirement."
Gillie Westwood said: "This decision wasn’t taken lightly as my nigh on 13 years with the GCA have been so much more than just a job and what I will miss most are the GCA members who make this industry so special."
A recruitment process is now under way, led by Dennis Espley and other committee members.
The 2012 GCA Conference is taking place from 23 -25 January at the Crowne Plaza Heythrop Park nr Chipping Norton, Oxfordshire.