Ian Boardman, Andy Campbell and Roger Crookes will be inspecting the GCA's 150 members, with a new environmental remit.
They will see if garden centres have a peat policy, Forest Stewardship Council policy, whether they recycle, promote the environmental benefits of plants, use local suppliers and collect rainwater.
GCA chief executive Gillie Westwood said: "As an industry we are green and we should be leading the way and shouting about the things we do
Garden centres were stung by criticism from green campaigner Jonathon Porritt at January's GCA conference that few backed up their environmental credentials with a credible environmental policy.
Last week the Government introduced a plan to cut peat sales at garden centres to zero by 2020 in a campaign fronted by TV gardener Diarmuid Gavin and backed by the HTA and Growing Media Initiative.