Celtica gigantea, formerly known to most gardeners as Stipa gigantea, is a bunchgrass of Mediterranean and Iberian origin that earns its name. The evergreen clump of fine grey-green leaves sits at about two feet, unassuming through autumn and winter, and then in spring the flowering stems shoot up to six or eight feet — a transformation that is genuinely surprising the first time it happens. Those stems carry large, open panicles of silver-purple florets that sway at the slightest breeze, catching the light in a way that few plants can match. Through summer the flowers dry to gold, and they hold that colour through autumn and into the following winter, giving months of changing ornamental value from a single flush of bloom.

It grows naturally in dry, rocky soils with excellent drainage and full sun, and it dislikes being waterlogged far more than it dislikes drought. Hardy from Zone 5 through Zone 8, it is among the more cold-tolerant of the warm-climate grasses, a quality that earned it the Royal Horticultural Society's Award of Garden Merit. Division is the preferred propagation method, done in mid-spring to early summer before the heat sets in. It can serve as a spectacular back-of-border specimen, a garden divider, or a focal point in a mediterranean-style planting. Songbirds find the seed heads appealing through winter, and deer tend to leave it alone.