Spotted knapweed is a thistle-like plant without the sharp spines and has pink-purple flowers. It competes with native plants and pasture.
Spotted knapweed grows to 1.2 m tall. It is a slender, upright, branched herb that looks like a thistle but without sharp spines on the leaves. It is a biennial or short lived perennial plant.
All leaves are grey-green and finely hairy to velvety. There are two types of leaves.
Leaves that grow in a clump (rosette) at the base of the plant that are:
Leaves that grow along the flower stem that are:
Seeds sometimes have a tuft of hairs (pappus), which is usually less than 3 mm long.
Spotted knapweed looks like some thistles. Unlike thistles, knapweeds don’t have sharp spines on the leaves or bracts.
Compared to other knapweeds:
Larkdaisy (Centratherum punctatum) also looks like knapweeds, but its leaves have serrated edges.
In Australia, spotted knapweed has only been found in the Australian Capital Territory. These plants have been controlled.
Spotted knapweed is native to eastern Europe. It was accidently introduced to North America where it has become a wide spread weed.
Spotted knapweed mostly grows in cool temperate areas with over 250 mm of rain per year. It grows in a wide range of soil types, though it prefers well drained soil to water logged soils. Overseas it is a weed of disturbed sites (e.g. overgrazed or cultivated paddocks, roadsides, creek lines), although it can invade non-disturbed areas.
Spotted knapweed seeds are spread by water, wind, soil, contaminated hay, vehicles or on clothing. Spotted knapweed seed can also be spread via wildlife and livestock, either on their fur or after being eaten.
Spotted knapweed grows and spreads from root fragments.
CABI (2019). Invasive Species Compendium, Data sheet, Centaurea stoebe subsp. micranthos(spotted knapweed) https://www.cabi.org/isc/datasheet/12040#todescription
Invasive Org (2018). spotted knapweed Centaurea stoebe ssp. micranthos (Gugler) Hayek. https://www.invasive.org/browse/subinfo.cfm?sub=3013
Mangin, A. R., & Hall, L. M. (2016). First report: spotted knapweed (Centaurea stoebe) resistance to auxinic herbicides. Canadian Journal of Plant Science, 96(6), 928-931.
Please do not attempt to treat or dispose of this weed yourself. Report this plant if you see it anywhere in NSW by calling the helpline listed at the top of this page immediately.
NSW DPI will lead an initial response for the treatment and disposal of the plant to stop it from spreading.
See Using herbicides for more information.
Glyphosate 360 g/L
Rate: 10 mL per 1 L water
Comments: Spot spray. For general weed control in domestic areas (home gardens), commercial, industrial and public service areas, agricultural buildings and other farm situations.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate
The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.
|All of NSW||General Biosecurity Duty
All plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
|All of NSW||
A person who deals with prohibited matter or a carrier of prohibited matter is guilty of an offence. A person who becomes aware of or suspects the presence of prohibited matter must immediately notify the Department of Primary Industries