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''Centaurea maculosa'', the spotted knapweed, is a species of ''Centaurea'' native to eastern Europe. ==Invasive plant== It has been introduced to North America,〔Mauer, T., Russo, M.J., and Evans, M. (2001). (Element stewardship abstract for ''Centaurea maculosa'', spotted knapweed ). The Nature Conservancy. Retrieved online: 14 July 2007.〕 where it is considered an invasive plant species in much of the western United States and Canada.〔 In 2000, ''C. maculosa'' occupied more than in the US. Knapweed is a pioneer species found in recently disturbed sites or openings. Once it has been established at a disturbed site, it continues to spread into the surrounding habitat. This species outcompetes natives through at least three methods: # A tap root that sucks up water faster than the root systems of its neighbors, # Quick spread through high seed production, and # Low palatability, meaning it is less likely to be chosen as food by herbivores. It is also suspected to be allelopathic, releasing a toxin from its roots that stunts the growth of nearby plants of other species. Its seed is an achene about a quarter of an inch long, with a small bristly pappus at the tip which makes the wind its primary means of dispersal. The leaves are a pale grayish-green. They are covered in fine short hairs. First year plants produce a basal rosette, alternate, up to long, deeply divided into lobes. It produces a stem in its second year of growth. Stem leaves are progressively less lobed, getting smaller toward the top. The stem is erect or ascending, slender, hairy and branching, and can grow up to three feet tall. Because cattle prefer the native bunchgrass over Knapweed, overgrazing occurs, increasing the density and range of knapweed infestations. Human disturbance is also a major cause of infestations. Knapweed readily establishes itself and quickly expands in all growth forms in places of human disturbance such as industrial sites, along roadsides,and along sandy riverbanks, and also has the potential to spread into undisturbed natural areas.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Centaurea maculosa」の詳細全文を読む スポンサード リンク
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