Plant Name Spotted Knapweed  
Scientific Name Centaurea Maculosa  
Family Aster  
Plant Type Biannual  
Start of Blooming Season June  
End of Blooming Season August  

 

Spotted knapweed is a invasive biannual or short lived perennial in the aster family. Spotted Knapweed is native to central Europe and east to central Russia. The plant was introduced into North America in the late 1800s as a contaminant of alfalfa or clover seed. Spotted knapweed may also have been introduced through soil used as ship ballast. The plant is found throughout the western United States and Canada although there is evidence that knapweed is rapidly spreading towards the East coast.

Although spotted knapweed is considered severely invasive; use has been found as a grazing plant for sheep.

Within the realm of naturopathic medicine and folklore, the roots and seeds of spotted knapweed are diaphoretic, diuretic, tonic and vulnerary. The plant once had a very high reputation as an ingredient of the Medieval 'salve', an ointment applied to heal wounds and treat skin infections.

Please note that MIROFOSS does not suggest in any way that plants should be used in place of proper medical and psychological care. This information is provided here as a reference only.

There is currently no confirmed data on the edibility of spotted knapweed.

Spotted Knapweed grows in meadow, cultivated beds, and thrives in recently disturbed soil. Spotted Knapweed is suitable for: light (sandy), medium (loamy) and heavy (clay) soils, prefers well-drained soil and can grow in nutritionally poor soil. Suitable pH: acid, neutral and basic (alkaline) soils and can grow in very alkaline soils. Spotted Knapweed cannot grow in the shade. It prefers dry or moist soil and can tolerate drought.

Soil Conditions
Soil Moisture
Sunlight
Notes:

Spotted Knapweed is a perennial with highly branched, wiry-stemmed, hairy stalks which can grow up to 90cm tall. The leaves are a pale grayish-green. They are covered in fine short hairs. First year plants produce a basal rosette, alternate, up to 150 mm long, deeply divided into lobes. The plant 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 one meter tall. During the summer spotted knapweed plants have multiple violet to lavender ray-less flowers. Spotted Knapweed is very hardy and easily overpowers other nearby plant species with a tap root that sucks up water faster than the root systems of its neighbours and releasing a toxin from its roots that stunts the growth of nearby plants of other species. Spotted Knapweed also produces a large number of seeds which ripen from August to October and can easily be spread. 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 flowers are hermaphrodite (have both male and female organs) and are pollinated by Bees, flies, lepidoptera, and by self.The plant is self-fertile.

Plant Height 30cm to 100cm
Habitat Roadsides, fields, freshly disturbed soil, and Waste Places
Leaves 10cm to 20cm long, highly dissected
Leaf Margin Ciliate
Leaf Venation Longitudinal
Stems highly branched wiry stems with fine hairs
Flowering Season June to August
Flower Type Rounded clusters of flowers 2.5cm wide that are prickly
Flower Colour lavender to violet
Pollination Insects, wind, self
Flower Gender Flowers are hermaphrodite and the plants are self-fertile
Fruit achene with small bristly pappus
USDA Zone 4A (-31.7°C to -34.4°C) cold weather limit

The following health hazards should be noted when handling or choosing a location to plant spotted knapweed:

SHARP HAZARD

Spotted Knapweed has thorns on the flowers.


INVASION ALERT

Spotted knapweed is a highly invasive species and is banned by many jurisdictions for deliberate cultivation. Check with local conservation authorities before attempting to cultivate this species.


-Click here- or on the thumbnail image to see an artist rendering, from The United States Department of Agriculture, of spotted knapweed. (This image will open in a new browser tab)

-Click here- or on the thumbnail image to see a magnified view, from The United States Department of Agriculture, of the seeds created by spotted knapweed for propagation. (This image will open in a new browser tab)

Spotted Knapweed can be translated into the following select languages:

Arabic   Bulgarian вид червена метличина Chinese (Sim) 矢车菊
Croatian različak Czech plevel Danish  
Dutch   Esperanto   Estonian Kaunokki
Finnish kaunokki French centaurée German Flockenblume
Greek   Hebrew   Hungarian búzavirág
Italian fiordaliso Japanese ヤグルマギク Korean 수레 국화 속
Low Saxon   Lithuanian Shui Norwegian  
Persian قنطوریون اسود Polish   Portuguese centáurea-maior
Romanian   Russian василек Slovak burinu
Spanish   Swedish   Tagalog  
Turkish mor top çiçekli bitki Ukrainian волошка Vietnamese cây xa cúc

The information provided in this conservation assessment has been provided by the Natureserve Database in conjuction with various federal, provincial, state, county, district, regional, and municipal governments as well as public and private conservation authorities. Information in this section is accurate from the last time this article was updated.
Spotted Knapweed has no conservation status as it is considered an exotic and or invasive species in North America.

The MIROFOSS database offers free printable garden tags for personal and non-profit use. These tags can be used to properly identify plant samples in a garden. Click on the tags shown on the the screen or -click here- to download a full size jpeg image for a spotted knapweed identification tag; which can be printed on paper or used with a plastic laser printer.

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Description / Application Frost, R. A., & Launchbaugh, K. L. (2003). "Prescription Grazing for Rangeland weed Management: A New Look at an Old Tool.". Rangelands.
Description DiTomasso, J.M. (2000). "Invasive weeds in rangelands: Species, impacts, and management". Weed Management: 255–265.
Folklore Somers, Paul (2008). A guide to invasive plants in Massachusetts. Massachusetts division of fisheries and wildlife. p. 39
Biology Roger L. Sheley, James S. Jacobs and Michael F. Carpinelli (April–Jne 1998). "Distribution, Biology, and Management of Diffuse Knapweed (Centaurea diffusa) and Spotted Knapweed (Centaurea maculosa)". Weed Technology: 353–362.
Biology John R. Lacey, Clayton B. Marlow and John R. Lane (1989). "Influence of spotted knapweed (centaurea maculosa) on surface runoff and sediment yield". weed technology: 627–631.
Biology Blair, Amy; Nissen, Scott j.; Hufbauer, Ruth A.; Brunk, Galen R. (September 2006). "A Lack of Evidence for an Ecological Role of the Putative Allelochemical (±)-Catechin in Spotted Knapweed". Journal of Chemical Ecology.
Image Rendering USDA-NRCS PLANTS Database / USDA NRCS. Wetland flora: Field office illustrated guide to plant species. USDA Natural Resources Conservation Service.
Environment National Audubon Society. Field Guide To Wildflowers (Eastern Region): Alfred A. Knopf. pp 415-420 ISBN 0-375-40232-2
Physical Identification National Audubon Society. Field Guide To Wildflowers (Eastern Region): Alfred A. Knopf. pp 415-420 ISBN 0-375-40232-2
April 02, 2015 The last time this page was updated
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