Koeleria glauca aka Blue Hair Grass

Koeleria glauca is a small grass from Europe and temperate Asia. Common names include blue meadow grass and large blue hairgrass. It belongs to the grass family, Poaceae. This perennial grows in the cool part of the year. It forms dense, round clumps rather than a broad, loose mass. Growth is slow, and plants can be short-lived. Hot weather may cause the grass to become partly dormant.

The narrow leaves give each clump a fine texture. Their colour ranges from blue-green to grey-green. The blades are hairless and have smooth edges. Some leaves remain through winter, making the plant semi-evergreen. Foliage mounds reach about 1 foot [0.3 m] tall and wide. Flower stems bring the total height to about 2 feet [0.61 m]. Reported garden heights range from 0.5–2 feet [0.15–0.61 m]. RHS gives an upper spread of about 1.6 feet [0.5 m].

Flowers appear in May and June on stems above the leaves. The panicles rise 0.5–1 foot [0.15–0.3 m] above the mound. They start pale, glossy green and turn silvery white. As they dry, they can take on a buff shade. Their narrow, upright form contrasts with the rounded leaf clumps. Growers can sow seed outdoors in spring or autumn. Division in mid-spring offers another way to make new plants.

Full sun and soil that drains well suit this grass best. It grows well in sandy soil with little organic matter. It tolerates drought and dry ground once growing in suitable soil. Missouri Botanical Garden warns against heavy clay, wet soil, and shade. RHS also lists partial shade and a wider soil range. RHS lists neutral and alkaline soils, while noting tolerance of acid conditions. Hardiness ratings are USDA zones 5–9 and RHS H5. Plants in USDA zone 5 benefit from a protected site.

Use it at border fronts, along edges, or in rock gardens. Groups can form a low ground cover beside paths or patios. It also suits containers and small garden spaces. The grass tolerates urban conditions and the effects of black walnut. Sources report few major pest or disease problems. Moist, rich border soil may limit life to two or three years. Cut plants to ground level in late winter for fresh growth. Old flower stems can also be removed before seed forms.