The display featured two roundabouts planted in the traditional bedding style, leading with small plants in the front row up to tall varieties in the centre, but formed of shrubs and herbaceous perennials.
The stand was put together by cash and carry supervisor Nigel Davies, assistant Emma Wright and production manager Paul Huggins.
Wright said: "To win the award is amazing. After we put all the effort in, we are dead chuffed."
Plants used on the shrub roundabout included Choisya ternata 'Sundance', Juniperus squamata 'Blue Carpet' Award of Garden Merit and Photinia fraseri 'Red Robin'.
Tamar managing director John Huibers said: "You can do fantastic things with hardy nursery stock. Permanent amenity displays can be created using only shrubs for low maintenance or herbaceous perennials which are high maintenance."
He said local authorities in Doncaster and Norfolk were already creating "fantastic" displays of low-maintenance, permanent planting.
But not all local authorities are so forward-thinking: "We offered to plant up the local roundabout and said we would also maintain it. But the local highways agency refused and said it would block the view."
First-time exhibitor Barrett of Boston won best product stand.