Tall Flatsedge

Cyperus eragrostis

Family: Cyperaceae

Other Common Names: lovegrass sedge, drain flat sedge, umbrella sedge, pale galingale
Weed class: monitor list
Year Listed: 2012
Native to: Parts of North and South America
Is this Weed Toxic?:

not known to be

Why Is It a Noxious Weed?

This plant is on the monitor list. Please contact Allison Bachner (abachner@kingcounty.gov) to report locations or for more information.

How would I identify it?

General Description

Tall flatsedge is a tufted, sedge-like, perennial plant with rhizomes.

Flower Description

Inflorescense is a spherical head of rays of spikelets (usually flat). Rays 3-10 and 1-2 inches (2.5-5 cm) long. Spikelets off-white to golden brown.

Leaf description

Leaves are flat or v-shaped, typically 9.8-19.7 inches (25-50 cm) long by 0.2-0.3 inches (5-8 mm) wide. The slender leaves grow from the base of the stem, and about 4-8 involucral leaf-like bracts exceed the inflorescence.

Stem description

Stems (culms) are triangular to round in cross section, hairless and 1.3-3 feet (40-90 cm) tall.

Fruit Seed Description

Dark brown to black achene, broadly ellipsoid 1.2–1.4 by 0.5–0.6 mm.

May Be Confused With

Similar to a Class B noxious weed, yellow nutsedge (Cyperus esculentus). Yellow nutsedge has a loose, open inflorescence--not in a dense, spherical cluster like tall flatsedge.

Where does it grow?

Tall flatsedge grows in damp grasslands, roadsides ditches, vernal pools, streambanks, irrigation channels and also grows in gardens, parks, disturbed sites, waste areas and damp habitats like wetlands.