Carex flacca
Carex flacca
Blue Sedge
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Taxonomy
Family Cyperaceae · Genus Carex
Description
Carex flacca, known for its cool blue-gray blades, is a tough, graceful sedge that forms tidy clumps and soft mats. It thrives in sun to part shade, shrugs off poor soils, and asks very little—making it a reliable, low-maintenance groundcover or meadow accent.
Common Names
Blue SedgeGlaucous SedgeBlue-gray SedgeBlue Meadow Sedge
Context
nativeRegion
Europe and Western Asia; naturalized in parts of North America.
usdaZones
4-9
companionPlants
Festuca glauca (Blue fescue), Nepeta (Catmint), Salvia nemorosa, Heuchera (Coral bells), Allium (ornamental onions), Sesleria caerulea (Blue moor grass)
culturalUses
Ornamental groundcover and meadow plant, erosion control on slopes, low-input lawn alternative, foliage contrast in borders.
Care
Care Requirements
LightFull sun to part shade; best blue color with 4–6+ hours of sun; tolerates bright shade.
WateringWater regularly to establish, then low to moderate needs; fairly drought tolerant; avoid waterlogged soils.
SoilWell-draining sandy or loamy soils; tolerates poor, alkaline, or calcareous conditions; pH neutral to alkaline.
FertilizerLight feeder; top-dress with compost in spring; avoid heavy nitrogen.
HumidityAverage ambient humidity; no special requirements.
TemperatureHardy in USDA 4–9; tolerates down to about -30°F (-34°C) and summer heat if soil drains well.
Growth & Life Cycle
HabitEvergreen to semi-evergreen clumping sedge that slowly spreads by short rhizomes into neat mats.
Mature Size8–18 in tall, 12–24+ in wide (20–45 cm tall, 30–60+ cm wide).
Growth RateModerate
BloomingLate spring to early summer; slender, inconspicuous brown to purplish flower spikes above foliage.
DormancySemi-evergreen; foliage may brown in cold winters and resumes growth in spring.
Propagation
MethodsDivision, Seed (cold stratified)
DifficultyEasy by division; moderate from seed.
Best SeasonEarly spring or early fall for division; sow seeds in fall or after cold stratification in late winter.
Maintenance & Notes
PruningComb or shear back ragged foliage in late winter or early spring before new growth; remove spent flower spikes if desired.
RepottingIn containers, divide or up-pot and refresh soil every 2–3 years in spring.
Pests & DiseasesGenerally trouble-free; occasional rust or leaf spot; crown/root rot in poorly drained soils; slugs/snails may nibble.
ToxicityConsidered non-toxic to people and pets.
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