This grower is fairly sure of this plant identification.
A shorter growing variety, with white flowers July/August. came to me named as Liriope alba, but may be a form of Ophiopogon
Liriope genus (Lilyturf). There are about 5 species of clump-forming, rhizomatous, evergreen perennials. The flowers range from white to pale purple.
They are fully to frost hardy and will require sun and well drained soil. Grow in full sun or part-shade. Before new leaves appear, trim back existing leaves for an overall improvement in shape and vigour.
Flower arranging, borders.