Centaurea biebersteinii - DC.
Spotted Star-thistle
Other English Common Names: Spotted Knapweed
Other Common Names: spotted knapweed
Synonym(s): Centaurea maculosa Lam. ;Centaurea stoebe ssp. micranthos (S. G. Gmelin ex Gugler) Hayek
Taxonomic Status: Accepted
Related ITIS Name(s): Centaurea stoebe ssp. micranthos (Gugler) Hayek (TSN 780711)
Unique Identifier: ELEMENT_GLOBAL.2.152552
Element Code: PDAST1Y0W0
Informal Taxonomy: Plants, Vascular - Flowering Plants - Aster Family
 
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Dicotyledoneae Asterales Asteraceae Centaurea
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Concept Reference
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Concept Reference: Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Centaurea biebersteinii
Taxonomic Comments: Kartesz (1994) gives Centaurea maculosa auct. non Lam. as a synonym of C. biebersteinii. Hickman (1993) accepts the name C. maculosa Lam. and states that is noxious weed in disturbed places and native to Europe. Name C. bierbersteinii followed here, with C. maculosa as a synonym. Native to Europe, exotic in North America, according to Jepson Manual.
Conservation Status
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NatureServe Status

Global Status: GNR
Global Status Last Changed: 10Nov1993
Rounded Global Status: GNR - Not Yet Ranked
Nation: United States
National Status: NNA
Nation: Canada
National Status: NNA (20Dec2017)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (SNA), Arizona (SNA), Arkansas (SNA), California (SNA), Colorado (SNR), Connecticut (SNA), Delaware (SNA), Florida (SNA), Hawaii (SNA), Idaho (SNA), Illinois (SNA), Indiana (SNA), Iowa (SNA), Kansas (SNA), Kentucky (SNA), Maine (SNA), Maryland (SNA), Massachusetts (SNR), Michigan (SNA), Minnesota (SNA), Missouri (SNA), Montana (SNA), Nevada (SNA), New Hampshire (SNA), New Jersey (SNA), New Mexico (SNA), New York (SNA), North Carolina (SNA), North Dakota (SNA), Ohio (SNA), Oregon (SNA), Pennsylvania (SNA), Rhode Island (SNA), South Carolina (SNA), South Dakota (SNA), Tennessee (SNA), Utah (SNA), Vermont (SNA), Virginia (SNA), Washington (SNA), West Virginia (SNA), Wisconsin (SNA), Wyoming (SNA)
Canada Alberta (SNA), British Columbia (SNA), New Brunswick (SNA), Nova Scotia (SNA), Ontario (SNA), Quebec (SNA), Yukon Territory (SNA)

Other Statuses

NatureServe Global Conservation Status Factors

Other NatureServe Conservation Status Information

Distribution
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U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
NOTE: The distribution shown may be incomplete, particularly for some rapidly spreading exotic species.

U.S. & Canada State/Province Distribution
United States ALexotic, ARexotic, AZexotic, CAexotic, COexotic, CTexotic, DEexotic, FLexotic, HIexotic, IAexotic, IDexotic, ILexotic, INexotic, KSexotic, KYexotic, MA, MDexotic, MEexotic, MIexotic, MNexotic, MOexotic, MTexotic, NCexotic, NDexotic, NHexotic, NJexotic, NMexotic, NVexotic, NYexotic, OHexotic, ORexotic, PAexotic, RIexotic, SCexotic, SDexotic, TNexotic, UTexotic, VAexotic, VTexotic, WAexotic, WIexotic, WVexotic, WYexotic
Canada ABexotic, BCexotic, NBexotic, NSexotic, ONexotic, QCexotic, YTexotic

Range Map
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Ecology & Life History Not yet assessed
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Economic Attributes Not yet assessed
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Management Summary Not yet assessed
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Population/Occurrence Delineation Not yet assessed
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Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank)
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Disclaimer: While I-Rank information is available over NatureServe Explorer, NatureServe is not actively developing or maintaining these data. Species with I-RANKs do not represent a random sample of species exotic in the United States; available assessments may be biased toward those species with higher-than-average impact.

I-Rank: High/Medium
Rounded I-Rank: High
I-Rank Reasons Summary: Centaurea biebersteinii, also known as C. maculosa or the spotted knapweed, is a non-native species in nearly every state in the United States. It is referred to as an aggressive invader that easily invades disturbed areas. Once established in disturbed areas, this species has the ability to invade undisturbed natural areas. It is most commonly found in the following natural areas: open forests, prairies, barrens and other types of grasslands. This species affects the abiotic process of the ecosystems it invades by more efficiently absorbing water and nutrients from the soil than the native species in the area, which ultimately causes declines in the native species populations. Further, this species not only alters the water-holding capacity of the soil, but also increases erosion. Overall, the spotted knapweed outcompetes native species, alters soil characteristics and is moderately difficult to control.
Subrank I - Ecological Impact: Medium
Subrank II - Current Distribution/Abundance: High
Subrank III - Trend in Distribution/Abundance: High/Medium
Subrank IV - Management Difficulty: High/Low
I-Rank Review Date: 15Sep2004
Evaluator: Oliver, L.
Native anywhere in the U.S?
Native Range: This species is native to Europe (Mauer et al. 2002).

Download "An Invasive Species Assessment Protocol: Evaluating Non-Native Plants for their Impact on Biodiversity". (PDF, 1.03MB)
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Screening Questions

S-1. Established outside cultivation as a non-native? YES
Comments: This species is established as a non-native in nearly every state in the United States (Kartesz 1999).

S-2. Present in conservation areas or other native species habitat? Yes
Comments: Small populations of this species tend only to invade disturbed sites, however, larger populations are capable of spreading into areas of conservation concern such as prairies and open forests (WI DNR).

Subrank I - Ecological Impact: Medium

1. Impact on Ecosystem Processes and System-wide Parameters:Moderate significance
Comments: The Spotted knapweed alters abiotic processes in several ways. This species easily extracts moisture and nutrients from the soil, and is better adapted than the native species inhabiting the area, of extracting nutrients. As this species invades, it alters the ecology of the ecosystem. Specifically, native species in areas where this non-native occurs tend to have network root systems and as the native species decline, their network root systems are replaced by the knapweed's taproot system. This taproot system alters the soil by lowering its water holding capability and increasing soil erosion (Maurer et al. 2002).

2. Impact on Ecological Community Structure:Medium/Low significance
Comments: By virtue of how the spotted knapweed invades, it probably does alter the ecosystem succession and ultimately affects the community structure. This species invades disturbed areas, and as the population grows and becomes established it is capable of invading undisturbed areas (Wilson and Randall 2003). As it invades undisturbed areas, it displaces native species (Wilson and Randall 2003, Maurer et al. 2002) and interrupts the natural succession of the land, thereby affecting at least one and possibly more vegetation layers.

3. Impact on Ecological Community Composition:High significance
Comments: The spotted knapweed is an aggressive invader of disturbed places and once established it is capable of invading nearby undisturbed, natural habitats (Wilson and Randall 2003). Once established in undisturbed areas, it displaces native species by altering the soil's water storage capacity and increasing erosion (Maurer et al. 2002). It's able to alter the soil in this way because of its taproot system which is better at extracting soil than the root systems of native plants (Maurer et al. 2002). The spotted knapweed has also been reported to be allelopathic, secreting toxins that kill nearby plants (WI DNR).

4. Impact on Individual Native Plant or Animal Species:Insignificant
Comments: No information was found that indicates that this knapweed disproportionately affects any individual native species.

5. Conservation Significance of the Communities and Native Species Threatened:Medium/Low significance
Comments: The spotted knapweed is known to invade prairies and grassland, and potentially threatens the rare and endangered prairie chicken that inhabits prairies (WI DNR).

Subrank II. Current Distribution and Abundance: High

6. Current Range Size in Nation:High significance
Comments: The spotted knapweed is known from nearly every state in the United States. The only states where it is not reported are: Texas, Oklahoma, Alaska, Mississippi and Georgia (Kartesz 1999).

7. Proportion of Current Range Where the Species is Negatively Impacting Biodiversity:Moderate significance
Comments: Kartesz 1999 reports that this species is considered noxious in most of the western United States. While 'noxious' includes a wide variety of negative impacts, it is probably safe to assume that the species has invaded natural areas within a portion of the western United States.

8. Proportion of Nation's Biogeographic Units Invaded:High/Moderate significance
Comments: This species probably is in many biogeographic provinces in the United States as it is known to invade both disturbed and undisturbed places (Wilson and Randall 2003).

9. Diversity of Habitats or Ecological Systems Invaded in Nation:Moderate significance
Comments: Known to invade open forests and grasslands (Wilson and Randall 2003). It is also known from prairies, barrens, pastures, hayfields, other types of grasslands (WI DNR).

Subrank III. Trend in Distribution and Abundance: High/Medium

10. Current Trend in Total Range within Nation:High/Moderate significance
Comments: This species is known as 'very aggressive' (Mauer et al. 2002) and is known to invade undisturbed areas (Wilson and Randall 2003). Also Mauer et al. 2002 make the following remark, 'Spotted Knapweed is increasing in its range and frequency in western North America'.

11. Proportion of Potential Range Currently Occupied:Low significance
Comments: Since this species has invaded nearly every state in the United States (Kartesz 1999), it has already invaded most of the potential area.

12. Long-distance Dispersal Potential within Nation:Moderate significance
Comments: Dispersal is usually passive. Long distance dispersal does take place however, by rodents, livestock, vehicles, hay or commercial seed (Mauer et al. 2002).

13. Local Range Expansion or Change in Abundance:High/Moderate significance
Comments: This species is categorized as an aggressive invader. It easily invades disturbed habitats and then once established, it is capable of invading undisturbed areas (Mauer et al. 2002).

14. Inherent Ability to Invade Conservation Areas and Other Native Species Habitats:High significance
Comments: This species is capable of changing the ecosystem so that it excludes native species, allowing it to invade even more aggressively into undisturbed, intact natural areas. Once it gets established in disturbed areas it has the ability to invade undisturbed sites. It does so by decreasing the available water and nutrients that are in the soil, which ultimately causes a decline in native species diversity (Mauer et al. 2002). It is also noted that spotted knapweed is allelopathic, meaning is secretes toxins into the soil that kills surrounding plants (WI DNR).

15. Similar Habitats Invaded Elsewhere:High/Low significance
Comments: Found in Canada (Kartesz 1999).

16. Reproductive Characteristics:Moderate significance
Comments: There are several reproductive characters that allow this species to be an aggressive and persistent invader. The spotted knapweed is self-compatible, its seeds may be viable in the soil for 8 years, plants can produce up to 600 seeds per year, and even when mowed in the early stages of flowering it can recover and produce more flowers and many seeds (Wilson and Randall 2003, Mauer et al. 2002).

Subrank IV. General Management Difficulty: High/Low

17. General Management Difficulty:Moderate significance
Comments: This species is moderately difficult to control. There are several methods that are somewhat effective. Mowing if done 10 days after flowering reduces the seed output, but doesn't eradicate populations. Herbicides are also effective, however, they don't prevent germination or reinfestation and can be expensive over large areas. Several biological control methods are available, including insects which either attack the flowers by laying eggs in them or eating the plant's roots. Biological control using insects does reduce populations, is inexpensive, and doesn't disturb the soil or surrounding vegetation, however, this method is slower than the others (Mauer et al. 2002).

18. Minimum Time Commitment:Medium/Low significance
Comments: Given that none of the control methods prevent germination or reinfestation (Mauer et al. 2002), several years would be needed to make a significant impact on areas with infestation of spotted knapweed.

19. Impacts of Management on Native Species:High/Low significance
Comments: The methods used to control this species would have a negative effect on native species in the surrounding area. Control methods include mowing, herbicide use and insects that destroy flowers and roots (Mauer et al. 1002).

20. Accessibility of Invaded Areas:Unknown
Authors/Contributors
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Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

References
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  • Douglas, G.W., G.D. Straley, and D. Meidinger, eds. 1998b. Illustrated Flora of British Columbia, Vol. 1, Gymnosperms and Dicotyledons (Aceraceae through Asteraceae). B.C. Minist. Environ., Lands and Parks, Wildl. Branch, and B.C. Minist. For. Res. Program. 436pp.

  • Flora of North America Editorial Committee. 2006a. Flora of North America North of Mexico. Vol. 19. Magnoliophyta: Asteridae, part 6: Asteraceae, part 1. Oxford University Press, New York. xxiv + 579 pp.

  • Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.

  • Kartesz, J.T. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. First edition. In: Kartesz, J.T., and C.A. Meacham. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden, Chapel Hill, N.C.

  • Mauer, T., M. J. Russo, and M. Evans. 1987. Element Stewardship Abstract for Centaurea maculosa. The Nature Conservancy, Arlington. http://tncweeds.ucdavis.edu/esadocs/centmacu.html

  • Moss, E.H. 1994. Flora of Alberta. Second Edition revised by J.G. Packer. University of Toronto Press, Toronto.

  • Wilson, L. M. and C. B. Randall. 2003. Biology and Biological Control of Knapweed. USDA-Forest Service Forest Health Technology Enterprise Team (FHTET)-2001-07. 2nd Edition. Available: http://www.invasive.org/weeds/knapweed/chapter1.html (accessed 18 August 2004).

  • Wisonsin Department of Natural Resources (WI DNR). Eek! - Nature Notes - Spotted Knapweed. Accessed 9/13/2004. Online at http://www.dnr.state.wi.us/org/caer/ce/eek/veg/plants/spottedknapweed.htm.

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