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Weed Identification

garden cornflower

Family

Asteraceae

Scientific Name

Centaurea cyanus

Other Common Names:

garden cornflower
garden cornflower

Synonyms (former Scientific Names):

Leucacantha cyanus

Habit

Erect winter annual that grows to 1.2 m tall with a taproot and often a weed in small grains.

Leaves

Leaves are alternate approximately 5 to 15 cm long and 1 cm wide, lance shaped to linear, hairy, and has entire or slightly toothed margins. Due to the leaf appearance, these plants are often confused for a grass.

Identifying Characteristics

An erect winter annual with long white hairs and blue, white, or pink flowers. Plants may reach 3.5 feet in height.This weed is sometimes confused with both Spotted Knapweed (Centaurea maculosa) and corn cockle (Agrostemma githago). However, spotted knapweed forms a basal rosette of leaves during the first year of growth and its leaves are much more deeply lobed than those of cornflower. Additionally, the leaves of corn cockle are joined across the stem and the stems of this plant are swollen at the nodes whereas neither of these characteristics occurs with spotted knapweed or cornflower.

Flower Seed Head

Many solitary heads are produced on long flower stalks (peduncles). Flowers are 2.5 to 5 cm wide and 1.5 to 3 cm long.They are pink, purple, white, and sometimes blue in color.

Seed Fruit

The seed is an achene that is about 4 mm long and 2 mm wide, and is gray in the middle and yellow brown on the ends with pubescense on one end.

Where Found

Found throughout the eastern half of the United States and also in the western states from California to Washington.

Growth Habit

upright and nonwoody

Thorns or Spines

not present

Approximate Flower Diameter

Varies: 
quarter
half dollar
larger

Dominant Flower Color

Varies: 
white
blue
purple
pink

Flower Symmetry

radial symmetery

Leaf Hairs

has hairs

Leaf Shape

Varies: 
needle
lance

Leaf Arrangement

alternate

Leaf Margin

Varies: 
entire
serrated

Leaf Structure

simple

Leaf Stalk

none

Stem Hairs

has hairs

Stem Cross Section

round or oval

Milky Sap

not present

Root Structure

taproot

Life Cycle

winter annual

Ochrea

not present

Plant Type

Herb