Carex flacca aka Blue Green Sedge

Carex flacca is a sedge in the Cyperaceae family. It is a perennial, living for more than one year. Its names include blue-green sedge and glaucous sedge. Its native range runs from Europe and the Mediterranean region to Pakistan. Britain and Ireland are part of that range. In the wild, it grows in grasslands rich in lime. It also grows in marshes, dunes, and estuaries, where rivers meet the sea. It comes from temperate climates.

The plant forms dense clumps and spreads through rhizomes, or stems below ground. Narrow leaves arch out from each clump. Their tops range from green to blue-green. Below, they have a pale, blue-gray cast. Sources give different heights for plants grown in gardens. Missouri Botanical Garden lists leaf heights of 0.5–0.8 feet [0.15–0.25 metres]. RHS gives a height of about 1.5 feet [0.45 metres]. The broader height range reaches 1.6 feet [0.5 metres]. The stated spread is about 1.5–3.3 feet [0.46–1 metre]. Growth is slow, but plants can form colonies over time.

Thin flower stems rise above the leaves in early summer. Missouri Botanical Garden notes light green blooms from June to July. Chicago Botanic Garden gives May to June as the bloom time. RHS notes purple-brown flower spikes on stems that arch. Each spike reaches about 0.13 feet [0.04 metres] long. The leaves' color draws more notice than the flowers. Leaves and ground cover are the main reasons gardeners grow it.

Moist soil is best, but clumps can take some drought once established. The plant accepts chalk, clay, loam, and sand. RHS favors a neutral to alkaline soil pH. It grows well in part shade and also takes deeper shade. Full sun suits it where summers stay cool. It can grow in shallow standing water at pond edges. Missouri Botanical Garden lists USDA zones 4–9. RHS rates it H7. Leaves stay green all year where winters are mild. In cold regions, cut off old leaves in late winter. Elsewhere, rake out worn leaves and old blooms in spring.

Grow it beneath trees, beside paths, or in shaded borders. It also suits rock gardens, rain gardens, and damp hollows. Pots or beds with firm bounds help check its spread. Its resistance to deer adds value in exposed gardens. RHS and Missouri Botanical Garden both report few pest or disease concerns. Divide clumps in early summer, or sow seed in spring.