Centaurea
From Freepedia
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Around 350-500 species; see text |
Centaurea is a genus of about 350-500 species of herbaceous thistles and thistle-like flowering plants in the family Asteraceae, mostly native to the Old World. Common names for different species include star thistle, cornflower, knapweed and bluet. Some species are cultivated as ornamental plants in gardens.
Species
Species in this genus include:
- Centaurea calcitrapa – Purple Star Thistle or Caltrop - Europe
- Centaurea cyanus – Cornflower
- Centaurea diffusa – Diffuse Knapweed
- Centaurea iberica Sprengle – A spiny Mediterranean species thought to be the "thistle" mentioned in Genesis
- Centaurea maculosa Lam. – Spotted Knapweed, an eastern European species introduced to the USA, now a pernicious and invasive weed which releases a toxin that reduces growth of forage species.
- Centaurea montana – Mountain Bluet
- Centaurea nigra – Black Knapweed or Common Knapweed
- Centaurea nigrescens – Tyrol Knapweed - South and Eastern Europe
- Centaurea repens L. – Russian Knapweed (also Turkestan Thistle) is a perennial, native to southern Russia and Asia Minor to Altai and Afghanistan. It is a pernicious weed within parts of its native range as well as in places where it has been accidentally naturalized. The flower head is lilac in color and not armed with spines.
- Centaurea scabiosa – Greater Knapweed
- Centaurea solstitialis L. – The Yellow Star Thistle, shown in the picture below, is an annual that grows to a height of 30-80 cm. This plant is widely naturalized outside of Europe where it is native.
Nectar
Image:Yellow star thistle.jpg Centaurea are copious nectar producers, especially on high-lime soils, and are major honey plants for beekeepers. Star thistle varietal honey is light and slightly tangy. It is one of the finest honeys produced in the US, but as it is abundant, some of it is fraudulently relabeled and sold as the scarce, expensive Sourwood honey of the Appalachian Mountains.
The high nectar yield of the genus makes it very attractive to insects such as butterflies and day-flying moths such as Six-spot Burnet. The larvae of some other Lepidoptera species such as Common Pug, The Engrailed, Grey Pug, Hebrew Character, Hummingbird Hawk-moth and Lime-speck Pug use this as a food plant.
Bibliography
- Mabberley, D.J. 1987. The Plant Book. A portable dictionary of the higher plants. Cambridge University Press, Cambridge. 706 p. ISBN 0 521 34060 8.
- Robbins, W.W., M. K. Bellue, and W. S. Ball. 1970. Weeds of California. State of California, Dept. of Agriculture. 547 p.
