Spotted Knapweed (Centaurea maculosa) |
Status: |
Listed Noxious Weed In Montana & North Dakota |
History: |
First Montana Specimen Collected 1 |
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County: |
Ravalli |
Year: |
1920 |
“A native of Europe, C. maculosa was accidentally introduced to North America most likely in the 1890s in alfalfa seed from Asia Minor (Maddox 1979).”
“Spotted knapweed was collected in Victoria, B.C. in 1893
(Moore and Frankton 1974). It is assumed that soil carried on ships as
ballast and unloaded in the port transported knapweed seed to this site
at that time (Roche et al. 1986). Although the earliest collections of C. maculosa
are from coastal areas of British Columbia and Washington, evidence of observed
densities and directions of spread suggest it has moved into Washington more
rapidly from the east (Roche et al. 1986). This species was abundant in Montana
before it became common in Washington (Roche et al 1986).” (Mauer, Russo & Evans) |
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Habitat: |
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Growth Habit: |
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Leaves: |
Alternate, simple, of several types: Upper leaves -- small, narrow, unbroken edge; Stem leaves -- intermediate in size, slight toothed margins; Basal leaves -- deeply notched.
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Stem: |
Slender Stems usually having many branches.
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Flower: |
Pink-purplish flower, also sometimes light purple or white. The flow heads bracts are colored have dark colored streaks giving the head a “spotted” appearance.
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Roots: |
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Seeds: |
Prolific seed producer. Can produce 1000 or more seed per plant with a viability of more than eight years.
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Other Notes: |
"It is not known how often livestock and wildlife eat knapweed seed heads. However, tests indicated that 11% of the seeds eaten by mule deer and 4% of the seeds
eaten by sheep, pass through their digestive systems, with a viability of
up to 22%. Viability was near zero for seeds that took longer than two
days to pass. The experiments were carried out by feeding mule deer and
sheep capsules of spotted knapweed seeds."
"Spotted knapweed has a reputation for exuding a poison that kills other
plants nearby. Infested lands may consist of nothing but acres and acres
of knapweed with seemingly lifeless soil beneath it." (Elpel)
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