Perennial Cornflower

Centaurea montana

Perennial Cornflower

Family: Asteraceae

Other Common Names: mountain bluet, mountain cornflower, mountain knapweed
Weed class: monitor list
Native to: Europe
Is this Weed Toxic?:

not known to be

Why Is It a Noxious Weed?

This plant is on the monitor list - it is not a listed noxious weed in Washington. Please contact its sponsor Julie Sanderson to report locations or for more information.

How would I identify it?

General Description

Perennial cornflower is a hairy perennial plant that spreads by creeping rhizomes. Plant grow up to 2-2.5 feet tall (60-80 cm).

Flower Description

Flowerheads solitary at stem tips (to rarely few). Bracts at the base of the flowerhead overlap like shingles (imbricate), with blackish-brown tips that are deeply toothed. Blooming flowerhead around 2 inches wide, inner flowers are violet while outer flowers are blue, enlarged and extending outward.

Leaf description

Leaves typically simple, with smooth margins and decurrent (leaf blade extending down along the stem)--forming wings on stem. Leaves lance-shaped to egg-shaped, thinly hairy to woollly, and 4-12 inches (10-30 cm) long. Lower leaves sometimes remotely dentate (toothed) to lobed along the edges.

Stem description

Stems are single to several, upright, simple or sparingly branched with hairs.

Fruit Seed Description

Seeds (cypselae) are brown, 5-6 mm long and have soft, appressed hairs. Each one has bristles on one end (a pappus) that are 0.5-1.5mm long.

May Be Confused With

It may be mistaken for another monitor list species, bachelor's button (Centaurea cyanus), which is an annual with narrow, smaller leaves, smaller outer flowers in the flowerhead and lacks rhizomes.

Where does it grow?

Grown as an ornamental, perennial cornflower can escape and grow in a variety of habitats including roadsides, woodlands, and sagebrush scrub.

How Does it Reproduce?

Plants spread by seed and vegetatively by rhizomes.

For More Information

Flora of North America Centaurea montana

Centaurea montana biography by the Alaska Exotic Plants Information Clearinghouse

WTU Image database for Centaurea montana

USDA Plants Database information on Centaurea montana

Additional Photos