WildFlower Turf, which claims to have pioneered flower turf in Britain, put a green roof onto a visitor centre at Paultons Park near Southampton.
The 1,250sq m roof brims with yarrow, plantain, bird's foot trefoil, wild-red clover and common sorrel, said managing director James Hewetson-Brown.
Unlike Sedum, mostly grown off crushed rubble, Hewetson-Brown's turf and flowers grew on a 100m organic substrate of various composts and nutrients, he added.
"Sedum is low growing and clinical in look," he said. "Our turf has no crushed brick substrate so is low-weight and holds moisture to support the wild flowers."
The flowers seeded annually so any drought patches would regenerate quickly. The roof slows run-off and is said to be good for sound and heat insulation.
WildFlower Turf has supplied lawn grass for Harry Potter's Hogwarts school and, more recently, for director Steven Spielberg's forthcoming movie War Horse.