Centaurea is a genus of between 350 and 600 species of herbaceous thistle-like flowering plants in the family Asteraceae. Members of the genus are found only north of the equator, mostly in the Eastern Hemisphere; the Middle East and surrounding regions are particularly species-rich. Although accurate information about the distribution of these plants in the Middle East is not available for us, but we estimate that the distribution of these plants in Iran is over several thousand hectares.

Common names of cornflowers

Common names for this genus are centaury, centory, starthistles, knapweeds, centaureas. Some vernacular name used for these plants is “loggerheads” or common knapweed or basketflowers but these are more commonly known as cornflowers in commercial world. Below you will find some of the commercial names of cornflower in different languages:

Aciano, Audifoin, Bachelor’s buttons, Barbeau, Bleuet, Bleuet des Champs, Bluebonnet, Bluebottle, Bluebow, Blue cap, Blue centaury, Casse-lunettes, Centaurea cyanus, Centaurea segetum, Centaurée bleue, Centaurée bleuet, Cyani blossoms, Cyani flos, Cyani flowers, Cyani petals, Flor celeste, Hurtsickle

To date, over 100 species of Centaurea are known in the world, that you can be supplied from Iran 4 kind of them.

1. Iranian knapweed (depressa)

blue cornflowerCentaurea depressa, the low cornflower, is a species of Centaurea. It is native to southwestern and central Asia. Its common name is Iranian knapweed. The plant grows in Iran to 0.3 m (1 ft) tall and flowers from April to August. It can grow in nutritionally poor soil and is drought tolerant. For this reason, the largest distribution of cornflowers in Iran is related to the Centaurea depressa.

Centaurea depressa is an annual plant that grows from 20–60 cm tall. Several stems grow from the base of the plant. They are openly branched and have a gray color with short hairs. The leaves are oblong blades that grow 5–10 cm long and have fine hairs on them. The florets are a dark blue.

2.Blue Cornflower (Centaurea cyanus)

Blue-CornflowerCentaurea cyanus, commonly known as cornflower or bachelor’s button, is an annual flowering plant in the family Asteraceae, native to Europe. In the past it often grew as a weed in cornfields, wheatfields, barleyfields, ryefields, or oatsfields, hence its name.

It is now endangered in part of Iran by agricultural intensification, particularly over-use of herbicides, destroying its habitat. It is also, however, through introduction as an ornamental plant in gardens and a seed contaminant in crop seeds, now naturalised in many other parts of Iran, including center, north, northwest and northeast Iran.

Cornflower is an annual plant growing to 40–90 cm tall, with grey-green branched stems. The leaves are lanceolate, 1–4 cm long. The flowers are most commonly an intense blue colour, produced in flowerheads (capitula) 1.5–3 cm diameter, with a ring of a few large, spreading ray florets surrounding a central cluster of disc florets. The blue pigment is protocyanin, which in roses is red. It flowers all summer.

3.Golden Cornflower (Centaurea behen)

Yellow-CornflowerCentaurea behen is a species of Centaurea that grows in the wild under full sun in northern Iraq and Armenia and in many other areas of Western and Central Asia with a roughly similar environment, stretching from Lebanon to Kazakhstan, particulary all over Iran.

The plant’s leaves near ground-level are relatively large, comparable to broad dock or spinach leaves. Rising above those leaves are branching stalks that carry much smaller lightweight leaves and, when in flower, small yellow flowers. Including the upper stalks, the plant is typically a little less than a meter high off the ground. The flowers of the plant contain many nectar which are useful for bee and honey production.

The plant has multiple thick roots. The roots have a brown skin on the outside and a white color internally. The roots come to commerce in a dried form, looking shrivelled, and then are ground to a powder, and used for several traditional herbal medicine purposes. The roots are called Behman Safed, also known as White Behmen, Safaid Behmen, in Ayurvedic Indian medicine. The plant is grown under cultivation in northern India for the medicinal use of its roots.

4.Yellow Cornflower (Centaurea solstitialis)

Golden-CornflowerCentaurea solstitialis, yellow star-thistle, is a member of the family Asteraceae, native to the Mediterranean Basin region. The plant is also known as golden starthistle, yellow cockspur and St. Barnaby’s thistle (or Barnaby thistle) The plant is a thorny winter annual species in the knapweed genus.

Centaurea solstitialis is an annual herb from the family Asteraceae. During the vegetative stage it forms a rosette of non-spiny leaves (5–20 cm diameter). As the summer approaches, it produces a flowering stem (1 m) which will produce numerous spinous capitula containing numerous (10-50) yellow flowers. Flowers within capitula are pollinated by insects and each capitula will produce a mix of (10-50) pappus and non-pappus seeds. It is an annual semelparous species, and will die after reproduction is completed, normally by the end of the summer.

Centaurea solstitialis is a weed also on its native European range (e.g., Turkey, Greece, Italy, France, Spain), consequently, it inhabits highly disturbed ruderal habitats, being typically found on roadsides and cereal crop margins. After introduction in several parts of the world as an exotic species (e.g., Australia, Argentina, Chile, United States), it has developed local adaptations to the different habitats colonized, and an incipient level of reproductive isolation between native and non-native ranges has been detected—a case ecological speciation.

Species similar to Centaurea solstitialis are purple star-thistle (Centaurea calcitrapa), sulphur star-thistle (Centaurea sulphurea), Maltese star-thistle (Centaurea melitensis), and rough star-thistle (Centaurea aspera).

It is grown as an ornamental plant in gardens, where several cultivars have been selected with varying pastel colours, including pink and purple. Cornflowers germinate quickly after planting. Light requirements: full sun. Water requirements: high-average water daily. Soil pH requirements: neutral (6.6-7.5) to mildly alkaline (7.6-7.8).

The edible flower of the cornflower can be used for culinary decoration, for example to add color to salads. Cornflowers have been used historically for their blue pigment. Cornflowers are often used as an ingredient in some tea blends and herbal teas. Cornflower seed is one of the favorite foods of the European goldfinch.