A nursery must grow more than 70 per cent of the plants it sells on its own premises to be part of the scheme.
More than 30 nurseries are already involved. The HEA has 300 members including non-nursery exhibitors.
HEA secretary Sarah Clare explained: "Joining the current trend towards buying local and supporting British horticulture, the scheme will help the public to identify home-grown plants within the ornamentals sector."
Participating nurseries will show a logo on their flower-show stands, and a leaflet explaining the scheme to the public will be produced.
Nurseries involved in the scheme sell directly to the public, supporting the local economy in their area.
Clare added: "Specialist nurseries provide a wealth of knowledge and a diversity of plants not seen in run-of-the-mill garden centres."