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Centaurea
Also called Starthistles, Star Thistle, Knapweeds, Star Thistles
Centaurea () is a genus of over 700 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.
Certain knapweeds have a tendency to dominate large stretches of landscape together with a few other plants, typically one or two grasses and as many other large herbaceous plants. The common knapweed (C. nigra) for example is plentiful in the mesotrophic grasslands of England and nearby regions. It is most prominently found in pastures or meadows dominated by cock's-foot (Dactylis glomerata) as well as either of crested dog's-tail (Cynosurus cristatus) and false oat-grass (Arrhenatherum elatius). It is also often found in mesotrophic grassland on rendzinas and similar calcareous soils in association with glaucous sedge (Carex flacca), sheep's fescue (Festuca ovina), and either tor-grass (Brachypodium pinnatum) and rough hawkbit (Leontodon hispidus), or upright brome (Bromus erectus). In these grasslands, greater knapweed (C. scabiosa) is found much more rarely by comparison, often in association with red fescue (Festuca rubra) in addition to cock's-foot and false oat-grass.
Despite the negative agricultural and environmental impacts of the more aggressive Centaurea species, there are many ways in which they benefit humans as well. For instance, due to their moderate to high nectar production, which can occur over a comparatively long duration, many species of Centaurea are popular food sources for insects that may otherwise attack certain crops. It may be advisable for some types of farms to allow certain Centaurea species, such as cornflower (C. cyanus) in a European setting, to grow adjacent to fields. These areas are known as beetle banks, though they support and attract a diversity of beneficial life beyond beetles. When certain Centaurea species are present, some pests may be drawn away from crops, and predatory insects and arachnids that feed upon pest insects will be better-supported by these more naturalized areas. They additionally have the beneficial aspect of supporting pollinators, unlike many field crops such as maize.
Centaurea acaulis · Akamas centaury · Centaurea alba · Centaurea ammocyanus · Rough star-thistle · Centaurea atropurpurea · Centaurea behen · Blessed Thistle · Red star-thistle · Karl-Henrikh's Centaury · Dusty miller · Centaurea collina
Text excerpted from the Wikipedia article Centaurea by its contributors, under CC BY-SA 4.0; the excerpts are shared under the same licence.
