The competition will feature in a column in The Sun by the newspaper's gardening editor Peter Seabrook.
Seabrook said: "The thrust of the column will be what excellent garden retailers we have and what a good job they do. This will be the start of a major campaign to encourage autumn gardening and will embrace the HTA's Plan It, Plant It campaign, the RHS and trade celebration of pansies and violas scheme, plus a big push on schools gardening in the new school year."
The Sun will have five regional winners and one overall national winner for the best retailer and there will be prizes for voters drawn at random to give consumers an incentive to vote.
Sun editorial will suggest voters look for quality plants at value for money prices backed by sound free advice from friendly staff.