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Species Brief

Centaurea stoebe subsp. micranthos, spotted knapweed

Written
July, 2026
Contributors
Ilana L. Abrahamson - 1st Compiler, Leila Duchac - 1st Editor

Abrahamson, Ilana L., compiler. 2026. Species Brief: Centaurea stoebe subsp. micranthos, spotted knapweed. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Missoula Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/species-briefs/censtom

DOI
10.2737/feis-species-brief-censtom

Scientific Name
Centaurea stoebe subsp. micranthos
Common Names
spotted knapweed
spotted starthistle
spotted star-thistle
bushy knapweed
FEIS Lifeform Type
Forb
Kingdom
Plantae
Class
Magnoliopsida (Dicot)
Order
Asterales
Family
Asteraceae
Genus
Centaurea
Nativity
Nonnative
Invasiveness
Invasive

This Species Brief is a concise summary of the biological, ecological, and fire‑related characteristics of an individual species derived from a Fire Effects Information System (FEIS) Species Review. Table 1 is derived from a standardized template and highlights these characteristics.

Table 1—Biological, ecological, and fire-related characteristics about spotted knapweed. Asterisks indicate areas of uncertainty or discrepancy. When asterisks are used, text in the justification field describes the uncertainty or discrepancy.
AttributeCharacteristicJustificationSource
Biological characteristics
Life formForbSpotted knapweed is a forb.FEIS: Botanical Description [1]
Typical lifespan1-5 years; 5-10 years; 11-20* yearsSpotted knapweed plants can live for at least 12 years, although plants over 7 years old have a high incidence of root rot. One study reported the average age of spotted knapweed was 3 years old on 5 sites and 5 years old on 6 sites.FEIS: Plant Longevity [1]
Life cyclePerennial; Biennial; Annual*Spotted knapweed is a perennial or biennial. An annual life cycle is rare and reported in West Virginia. In Montana it is predominantly a perennial.FEIS: Botanical Description [1]
Drought toleranceModerate*Spotted knapweed grows on dry to moist sites and has a deep taproot that may help plants persist under dry conditions. However, drought often contributes to population decline and seedling mortality, so it is not reliably drought tolerant.FEIS: Soil moisture; Botanical Description; Population Structure and Growth [1]
Rooting depthDeepSpotted knapweed has a deep, stout taproot. One study reported the average taproot length exceeded 30 cm in Corvallis, Montana.FEIS: Botanical Description [1]
Tree bark thickness at maturityN/AThis attribute applies to trees.FEIS: Botanical Description [1]
Tree that sheds low branchesN/AThis attribute applies to trees.FEIS: Botanical Description [1]
Reproduction and Regeneration
Adventitious budsRoot crownSpotted knapweed can sometimes form new rosettes immediately adjacent to the parent plant. It also sprouts from the root crown after defoliation or top-kill.FEIS: Vegetative Reproduction and Regeneration [1]
Time to reproductive maturity0-1 year*; 2-5 yearsSpotted knapweed seedlings can develop into rosettes, bolt, and flower during the year of seedling emergence, but this is rare. Seedlings can also develop into rosettes throughout the summer, overwinter, and bolt during the following year, but many plants live as rosettes for many years before bolting.FEIS: Seasonal Development; Plant Growth [1]
Soil seed bank longevityLong-term persistent (>5 years)Dormant, viable seeds can survive in the soil seed bank for at least 8 years.FEIS: Seed Banking [1]
Serotinous conesN/AThis attribute applies to conifers. Spotted knapweed flowerheads produce achenes or cypselae.FEIS: Botanical Description [1]
Seed dispersal mechanismGravity; Wind; Animal; Water*Seeds are typically dispersed short distances by gravity and wind. Seeds are also dispersed by animals, water, and vehicles.FEIS: Seed Dispersal [1]
Seed dispersal distanceShort (mostly under parent plant); Medium*; Long (>1 km)*Most seeds disperse less than 1 m from their parent plant, but animals including domestic sheep, mule deer, and great horned owls can facilitate long-distance dispersal.FEIS: Seed Dispersal [1]
Optimal conditions for seedling establishmentBare soil; SunSeeds germinate and seedlings establish best on moist, disturbed soils. Disturbance favors spotted knapweed establishment by increasing bare ground, reducing litter and vegetation, and increasing sunlight to the soil surface.FEIS: Seedling Establishment and Mortality [1]
Successional Status
Shade toleranceShade intolerantSpotted knapweed does not grow well on shaded sites and commonly grows in open areas. Root mass, foliage, and crown size are less in shade than in full light.FEIS: Plant Growth [1]
Successional statusEarly; Mid*Spotted knapweed frequently occurs in early-successional forests but is uncommon in older stands. Disturbance creates favorable conditions for spotted knapweed seedlings, and it often establishes shortly after disturbances that open the tree canopy. It is also common in old fields and has been reported in mid-successional grasslands.FEIS: Succession [1]
Fire
Primary fire response(s) or adaptation(s)Recover/Resprout; RecruitSpotted knapweed has a large, perennial taproot and is likely to survive and sprout after fire if the root crown is not killed. It can also establish from undamaged seeds in the soil seed bank and from seeds dispersed from off-site sources.FEIS: Fire Adaptations [1]
Germination is fire stimulatedRarely/NoHeating or burning of seeds generally reduces spotted knapweed germination and seedling emergence.FEIS: Immediate Fire Effects [1]
Flowering/fruiting is fire stimulatedRarely/NoIf low-severity fire occurs prior to bolting, spotted knapweed is likely to sprout and produce flowering stems in the same growing season, but this reflects recovery of surviving plants rather than fire enhancing flowering. Fire at the flowering stage can reduce spotted knapweed reproduction.FEIS: Immediate Fire Effects; Postfire Reproduction [1]
Season when it is most sensitive to fireSpring; SummerSpotted knapweed seedlings tend to be most sensitive to fire during spring, but adult plants are less sensitive to season of fire. Spring prescribed fires can help reduce spotted knapweed reproduction and establishment, while frequent summer fire may be most effective at reducing adult abundance.FEIS: Immediate Fire Effects; Plant Response to Fire [1]
Plant flammabilityLowSpotted knapweed does not carry fire as readily as grasses in invaded communities. Its stems have high amounts of silica that thwart attempts at burning, and green plants are too moist to carry fire.FEIS: Fuel Characteristics [1]
Early colonizer/recolonizer of burned or disturbed sitesFrequentlySpotted knapweed commonly occurs in disturbed and burned areas and often increases abundance after fire; however, postfire abundance varies by plant community, weather, fire characteristics, and phenology.FEIS: Succession; Plant Response to Fire [1]
Effect of fire exclusion on populationInsufficient informationThe source does not provide explicit information about the effect of fire exclusion on spotted knapweed populations. It is most invasive in grasslands semi-arid shrublands, woodlands, and open forests, where fire exclusion would have varied effects. Spotted knapweed would likely respond differently in each community.FEIS: [1]
Is this species typically managed with prescribed fire?SometimesPrescribed fire has been used to control spotted knapweed, but its effectiveness for killing the plants or reducing population growth depends on the plant community and fire characteristics.FEIS: Fire as a Control Agent [1]
Predominant historical fire frequencies of ecosystem where it most commonly occursInsufficient informationSpotted knapweed is most invasive in grasslands, semi-arid shrublands, woodlands, and open forests that have a range of historical fire frequencies.FEIS: Fire Regimes; Plant Communities [1]
Predominant historical fire severity where it most commonly occursInsufficient informationSpotted knapweed is most invasive in grasslands, semi-arid shrublands, woodlands, and open forests that have a range of historical fire severities.FEIS: Fire Regimes; Plant Communities [1]
Predominant historical fire regime group where it most commonly occursInsufficient informationSpotted knapweed is most invasive in grasslands, semi-arid shrublands, woodlands, and open forests that have a range of  historical fire regime groups.FEIS: Fire Regimes [1]
Alters historical fuel characteristics of ecosystems where it occursYes, invasive species*While it is unclear how fire regimes of invaded plant communities might affect or be affected by spotted knapweed populations, spotted knapweed does not carry fire as well as grasses. Dense spotted knapweed populations may change the fuel characteristics on sites formerly dominated by grasses and thus alter fire regime characteristics.FEIS: Fire Regimes [1]

1. Innes, Robin J. 2021. Centaurea stoebe subsp. micranthos, spotted knapweed. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Missoula Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/species-reviews/censtom

Species Reviews
AbbreviationTitleCommon TitleScientific Title
CENSTOMCentaurea stoebe subsp. micranthos, spotted knapweedspotted knapweedCentaurea stoebe subsp. micranthos
Fire Regimes
TitleTypeYear
Fire regimes in Hawai'ian plant communitiesSynthesis2013
Fire regimes in jack pine communitiesReport2026
Fire regimes of Appalachian dry oak-pine communitiesReport2026
Fire regimes of Appalachian mixed-hardwood communitiesReport2026
Fire regimes of Appalachian riparian and floodplain communitiesReport2026
Fire regimes of California low-elevation grasslandsReport2026
Fire regimes of California montane mixed-conifer communitiesReport2018
Fire regimes of California pinyon-juniper communitiesReport2018
Fire regimes of Columbia Plateau grasslands and steppe communitiesReport2026
Fire regimes of conifer forests in the Blue MountainsSynthesis2017
Fire regimes of East Cascades ponderosa pine and montane mixed-conifer communitiesSynthesis2024
Fire regimes of eastern glades and barrensReport2026
Fire regimes of Great Basin desert grassland communitiesReport2026
Fire regimes of Great Basin mixed-conifer communitiesReport2026
Fire regimes of Great Basin pinyon-juniper communitiesReport2026
Fire regimes of Great Basin subalpine mixed-conifer communitiesReport2026
Fire regimes of Great Lakes riparian and floodplain communitiesReport2026
Fire regimes of intermountain basins semi-desert shrub-steppe communitiesReport2026
Fire regimes of intermountain riparian communitiesReport2026
Fire regimes of juniper communities in the Columbia and northern Great basinsSynthesis2019
Fire regimes of Madrean pine-oak-juniper communitiesReport2026
Fire regimes of Midwest oak savanna and woodland communitiesReport2026
Fire regimes of Midwest riparian communitiesReport2026
Fire regimes of mixed dwarf sagebrush communitiesReport2026
Fire regimes of montane riparian communities in California and southwestern OregonSynthesis2015
Fire regimes of mountain big sagebrush communitiesSynthesis2018
Fire regimes of northeastern dry-mesic oak communitiesReport2026
Fire regimes of northeastern riparian and floodplain communitiesReport2026
Fire regimes of northern Atlantic coastal plain communitiesReport2026
Fire regimes of northern mixed-hardwood communitiesReport2026
Fire regimes of northern Rocky Mountain juniper communitiesReport2026
Fire regimes of northern Rocky Mountain montane mixed-conifer communitiesReport2026
Fire regimes of Northern Rocky Mountain ponderosa pine communitiesSynthesis2016
Fire regimes of northwestern montane and foothill grassland communitiesReport2026
Fire regimes of Pacific Northwest montane grassland communitiesReport2026
Fire regimes of plains grassland and prairie ecosystemsSynthesis2021
Fire regimes of ponderosa pine communities in Arizona and western New MexicoReport2026
Fire regimes of ponderosa pine communities in the Black Hills and surrounding areasSynthesis2017
Fire regimes of ponderosa pine communities in Utah and NevadaReport2026
Fire regimes of ponderosa pine ecosystems in Colorado: A systematic review and meta-analysisSynthesis2019
Fire regimes of ponderosa pine ecosystems in two ecoregions of New MexicoSynthesis2023
Fire regimes of red pine-eastern white pine communitiesReport2026
Fire regimes of Rocky Mountain Douglas-fir communitiesReport2026
Fire regimes of Rocky Mountain lodgepole pine communitiesReport2026
Fire regimes of Rocky Mountain riparian communitiesReport2026
Fire regimes of Rocky Mountain subalpine mixed-conifer communitiesReport2026
Fire regimes of Rocky Mountain western redcedar communitiesReport2026
Fire regimes of saltbush desert scrub communitiesReport2026
Fire regimes of Sierra Nevada hardwood communitiesReport2019
Fire regimes of southern Rocky Mountain juniper communitiesReport2026
Fire regimes of southern Rocky Mountain mixed-conifer communitiesReport2026
Fire regimes of southern Rocky Mountain quaking aspen communitiesReport2026
Fire regimes of southwestern grassland and steppe communitiesReport2026
Fire regimes of southwestern pinyon-juniper communitiesReport2026
Fire regimes of woody riparian communities of the Central Valley, CaliforniaSynthesis2015
Fire regimes of Wyoming big sagebrush and basin big sagebrush communitiesSynthesis2019
Fire regimes of Wyoming ponderosa pine communitiesReport2026
Fire Studies
TitleAuthorsTypeYear
Vegetation response to restoration treatments in ponderosa pine-Douglas-fir forests of western MontanaMetlen et al.Research Project Summary2006
Last updated August 20, 2026
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