Centaurea (Star thistles, Knapweed, Hardhead, and Loggerhead) is a genus of herbaceous thistle-like flowering plants in family Asteraceae, comprising about 450 species. Most of the species are native to Palaearctic, where the Middle East and surrounding regions are particularly species-rich.
Centaurea contains annuals and perennials ornamental plants which are invaluable in wildflower and cottage garden and also good as cut flowers.. It is a robust weedy plant with colorful 'flowers' (actually pseudanthium inflorescences) that come in colors ranging from intense blues, reds and yellows to any mixture of these and lighter shades towards white. Often, the sterile disk flowers are in much darker or lighter color than the ray flowers.
Due to the habit of dominating ecosystems under good conditions, many centaurea species can become invasive weeds in regions where they are not native. Cantaurea species are copious nectar producers, especially on high-lime soils. The high nectar yield of the genus makes it very attractive to pollinators such as butterflies. Larvae of some Lepidoptera species also use Centaurea species as food plants. Several species of Lepidoptera are used in biological control of invasive kanpweeds and starthistles.
Centaurea montana (Perennial Cornflower, Mountain Cornflower, Bachelor's Button, Montane Knapweed or Mountain Bluet), 40 x 60 cm, is endemic to Europe. It grows in meadows and open woodlands in t he upper montane and sub-alpine zones. It bears beautiful blue flowers from May to August. Centaurea montana grows best in sunny positions and can tolerate a light shade. It grows well in soils varying from light sand to heavy clay, acid, neutral or very alkaline. It can tolerate drought but cannot tolerate waterlogged conditions. The leaves are readily eaten by squirrels.
Centaurea macrocephala (Globe Knapseed, Armenian Basketflower) cangrow up to 1 meter tall. It is a good middle-of-the-border plant, producing large yellow, thistle-like flowerheads, which make very popular subjects for dried-flower arrangements.
Centaurea cyanus (Cornflower, Bachelor's button, Bluebottle, Boutonniere flower, Hurtsickle) is an annual plant which bears blue, pink, purple or white flowers. The flowers attract a wide range of insects which in turn bring birds in their wake. The seedheads are useful for tits and finches.
Centaurea nigra (Lesser Knapweed, Common Knapweed and Black Knapweed) is native to Europe and is a host to a range of insects, which will attract birds, and the seedheads will attract finches in winter.
Plant Centaurea in full sun and in well-drained soil. Propagation is by seed in spring; divide perennials in autumn. Centaurea is quite hardy and disease that affect the plant is mildew.
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Luc Viatour
