PERENNIAL - Japanese Silver Grass Japanese silver grass and its cultivars are showy ornamental grasses useful as accent plants, hedges, or screens. They are warm-season grasses, so they green up in late spring or early summer and bloom in mid to late summer or fall. The flowers are attractive feather plumes in silver, tan, or reddish, becoming fluffy and white in winter. The flowers persist through the winter. In winter, the leaves take on a reddish or bronzy color.