The Ruxley Rose award, which is presented annually, recognises excellent quality and range of plants.
GCA chairman Peter Burks said: "The Ruxley Rose competition focuses specifically on our members’ outdoor plant areas and is regarded as one of our most prestigious awards.
"This year we have changed our judging criteria. Now 50 per cent of the overall mark comes from the spring inspections, which have already taken place and 50 per cent will come from the judges’ visit in autumn.
"There is a new form that will be used for the autumn inspection, which looks similar in style to the spring inspection form but it has a number of criteria that are unique to enable the judges to assess creativity and commerciality."
The judging begins in all areas in September, there will be one or two regional judges for each area and each judge will put forward two finalists, one in the Destination Garden Centre category and one in the Garden Centre category, to go through to the national final.
He added: "Our members that reach the national final will then receive a second visit from the national judge. The overall winners for each category will be announced at our annual conference in January."
The judges of the Ruxley Rose competition will be looking at the quality, range and presentation of plants. They will also consider the layout and flow, merchandising and stock management, signage and point of sale.
Burks added: "Garden centres will be judged on their staff’s customer awareness and interactions, the promotions that they run and the displays they have created. The judges will also be looking for the wow factor.
"There are many benefits to taking part in the Ruxley Rose competition, the chance to win the prestigious award, an opportunity to motivate the plant area team at an important time of year. But also it is an independent and alternative view on our members’ plant areas, on which they will receive specific feedback following the judges visit.
"Our members take a great deal of pride in their outdoor plant areas so the competition is bound to be stiff. We’d like to wish all our members who sign up to take part the best of luck."