Greater knapweed is a invasive biannual or short lived perennial in the aster family. Greater 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. Greater 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 greater 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 greater 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 greater knapweed.

Greater Knapweed grows in meadow, cultivated beds, and thrives in recently disturbed soil. Greater 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. Greater Knapweed cannot grow in the shade. It prefers dry or moist soil and can tolerate drought.

Soil Conditions
Soil Moisture
Sunlight
Notes:

Greater 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 greater knapweed plants have multiple violet to lavender ray-less flowers. Greater 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. Greater 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 greater knapweed:

	SHARP HAZARD Greater Knapweed has thorns on the flowers.
	INVASION ALERT Greater 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 greater knapweed. (This image will open in a new browser tab)

Greater 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.
	Greater 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 greater knapweed identification tag; which can be printed on paper or used with a plastic laser printer.

What's this? This is a QR code (short for Quick Response) which gives fast-track access to MIROFOSS articles. QR Codes are barcodes that can be read by smart phone cameras. This QR Code is unique to this MIROFOSS article. What can I do with it? You can copy and print the QR code to a plant label, poster, book, web site, magazines, or newspaper so smart phone users can scan the QR Code which automatically takes them to this specific article.

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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