Following successful inspections the Garden Centre Association signed up five more members last month.
Thetford Garden Centre, Norfolk, Pacific Nurseries, West Midlands, and Thirsk Garden Centre, Yorkshire, were approved as new full members at the body's recent Executive Committee meeting.
Two subsidiary members, Millbrook Garden Centre, Kent, and Creative Gardens, County Antrim, were also approved.
GCA chief executive, Iain Wylie, said: "We would like to welcome all our new members on board and look forward to working with them."
Director of Thetford Garden Centre, Lucy Nixon, said: "We are delighted to be a member of the GCA. We believe it will help elevate us to the next level in terms of overall standards.
"As a member, our customers can be assured that we are committed to providing excellent levels of service and offering them quality plants. The whole team here are really proud to be a part of the GCA."
The GCA represents nearly 200 garden centres nationwide and through the sharing of information and its inspection programme, helps members to achieve high standards of customer service and plant quality.