However, a treated area must be monitored for several years and retreated as necessary for seedling control. Flowering occurs from June to September. Knapweed is a rather robust plant that can be found in dry, infertile soil, vacant lots, near railroad tracks, roadsides, coastlines and high lime or salt areas. The black tipped bracts found below the flower petals are the key feature to distinguish spotted knapweed from other knapweed species. If the plant is not flowering, search for last seasons flower stalk and identify the plant based on the flower bracts. Foliage. Dead spotted knapweed stems generally remain erect during the winter unless crushed by heavy snow-pack. Figure 5. spotted knapweed CEMA4: Centaurea maculosa auct. Russian knapweed roots are brown to black in color with a scaley, bark-like appearance and because it is perennial have root buds (right). Spotted Knapweed is one of 3 targeted plant species in Minnesota with an active bio-control program, the other 2 species are leafy spurge and purple loosestrife. Spotted Knapweed Centaurea stoebe An increasingly common, alien invasive species from Europe, Spotted Knapweed is plentiful in disturbed ground and even grows abundantly on the poor soils of the Magnasite Plant at Cape May Point due to its tolerance of semi-arid conditions. NUTRIENT VALUE The rosettes and young flowers of spotted knapweed have some nutritive value. Spotted Knapweed Identification and Management Background Information History and Impacts Spotted knapweed (Centaurea stoebe synonyms C. biebersteinii and C. maculosa) is native to Central, Eastern and Southeastern Europe. Can be a skin irritant. Pasture and rangeland. maculosa Common names: spotted knapweed Centaurea maculosa (spotted knapweed) is a biennial to short-lived perennial (family Asteraceae). Centaurea stoebe is a bushy, winter-hardy, upright perennial forb living 3 - 5 years or sometimes longer, with a deep taproot. Seed remains viable in the soil five years or more, so infestations may occur a number of years after vegetative plants have been eliminated. During the winter, knapweed plants will break off at the base of the stem and form tumbleweeds. See also: Invasive Plant Fact Sheets for plant species (trees, shrubs, vines, herbs and aquatic plants) that have impacted the state's natural lands In general, the knapweed infestations are small enough that herbicide and hand removal are the best and most cost-effective treatments in North Dakota. Centaurea stoebe . Seeds are dispersed by rodents, livestock and commercial hay. A study by Kelsey and Mihalovich (1987) found that spotted knapweed collected before flowering contained neutral detergent fiber (24.2-53.0% in dry weight), ether extract (3.1-9.0%), crude protein (6.2-18.2%), total non-structural carbohydrates (11.0- 27.5%), ash (4.9 to 9.3%), in vitro dry … Russian knapweed is one of the most difficult perennial weeds to control. Rosette leaves grow up to 6” long. Diffuse knapweed is a biennial or short-lived perennial with a deep taproot in the Aster Family that is similar to the more common spotted knapweed, but is generally shorter and its upper stems have numerous spreading branches giving the plant a ball shape. People are the major cause of knapweed spread. The weed emerges in the spring from roots and grows 1 to 3 feet tall (Figure 2). Then the areas should be treated with a herbicide to prevent reinfestation from seedlings. Wear gloves, long sleeves, and pants when handling. Allelopathic (able to stop the germination or growth of other plants), and can hybridize, making identification difficult. Spotted Knapweed was formerly (or incorrectly) known as Centaurea biebersteinii and Centaurea maculosa . Knapweed often spreads to a new site by seed in hay, on vehicles, or in contaminated seed (Figure 1). It was introduced to North America in the 1890s as a contaminant in agricultural seed and through soil discarded from ship ballast. Photos 3 and 4 courtesy of Dr. Steve Dewey, retired, Utah State Univ., Logan. Yellow starthistle (Centaurea solstitialis L.) is also a member of the knapweed family and is discussed in a separate bulletin (W-1411). It is also an invasive species in the United States, and particularly widespread in dryer regions of the Pacific Northwest. Control strategies: Removing the entire plant before they go to seed can help with small populations.Always wear gloves when handling as it is thought that Spotted knapweed may contain a cancer-causing substance. Knapweed reproduces by seed and can regenerate from the crown as well as by perennial root spread. Centaurea stoebe ssp. It is very difficult to distinguish knapweed species based on the rosette alone. Knapweed Root Weevil Cyphocleonus achates. flies feed on the seed while Larinus spp. Diffuse knapweed can spread as quickly as spotted knapweed, but Russian knapweed spreads much slower. Can persist as a rosette for one to four years. A careful follow-up program is necessary to control missed plants and seedlings. Leaves of bolted plant are alternate, grayish, hoary; divided into lance-shaped lobes. Flower bracts are the key distinguishing feature between spotted and diffuse knapweed. Spotted knapweed is found in artificial corridors such as gravel pits, railroad beds and field margins, and can spread to adjacent intact woodlands and prairies. Russian knapweed is a long-lived, deep-rooted perennial with growth characteristics similar to Canada thistle. Return to Land Gallery. Rodney G. Lym Professor Department of Plant Sciences. This weevil prefers hot, dry sites with loose, well-drained, coarse soils. Asteraceae or Sunflower Family Centaurea stoebe (syn. The flowers of Russian knapweed vary from light pink to lavender (Figure 3). micranthos Photo courtesy Bob Case. Black-tipped flower head bracts give plants a spotted appearance. It is often found in areas with a supplemental water source such as the Little Missouri and Heart Rivers in North Dakota. We are OPEN for the 2020 season. Angela Gupta, Extension educator; Amy Rager, Extension educator; Megan M. Weber, Extension educator. Knapweed infestations in North Dakota have been found primarily along highways, waterways, railroad tracks, pipelines and recently constructed utility lines. These three knapweeds already infest more acreage than leafy spurge in Montana and Minnesota, and have been found in over 20 counties in North Dakota. 2020 Small, brownish, oblong seeds have small tuft of bristles; appear from June to February. Spotted knapweed has few natural enemies and is not preferred by livestock as forage. Spotted knapweed is a biennial or short-lived perennial herbaceous plant that grows two to three feet tall. The largest infestations generally are found in southwestern North Dakota. non Lam. Cattle and other animals avoid eating it so it can cause large reductions in available food for grazing animals. Appearance. Spotted & Diffuse Knapweed Species Centaurea biebersteinii & Centaurea diffusa. Knapweeds are spread readily in hay and on vehicle undercarriages. CAUTION: Can cause skin irritations for some. Once established, Russian knapweed spreads mainly by underground root stocks as seed production is limited compared to other knapweed species. Identification. Spotted knapweed is an invasive species. The University of Minnesota is an equal opportunity educator and employer. Land Grant. Excluding flowers and spines, heads are about 3/16\" in diameter and 5/16\" tall. Spotted knapweed is a native of Europe and Asia. A large, conspicuous insect, it lays its eggs on the top of the knapweed's root crown. North Dakota is being threatened by three noxious weeds that could infest more acreage in the state and at a faster rate than leafy spurge. The physical appearance of diffuse knapweed is similar to spotted knapweed, except diffuse knapweed is generally shorter and more highly branched. Russian knapweed [Rhaponticum repens (L.) Hidalgo]. Also, rosettes of diffuse knapweed have more finely divided leaves than those of spotted knapweed (Figure 2). Consult the herbicide for use and grazing restrictions. It outcompetes native plant species, reduces native plant and animal biodiversity, and decreases forage production for livestock and wildlife. The best knapweed control is prevention, and to keep an infestation from becoming established you must correctly identify the plant. Attempts to control spotted and diffuse knapweed with insects have been in progress since the 1970s. Leaves become smaller as they advance up the stem. Consult Extension Circular W-253 “North Dakota Weed Control Guide” for additional information concerning herbicides for knapweed control. Watch for new infestations along any publicly traveled route, where livestock are fed, or in disturbed areas. The spiny bracts resemble a crab in appearance, are very sharp, and can puncture skin if touched. Diffuse knapweed flowers from July to September. Spotted knapweed can reach 1.5 m in height with several upright stems from a stout taproot. The plant grows 2 to 4 feet tall and can have one or more stems with pale green leaves which are 1 to 3 inches long. ... CT-USDA NRCS Invasive Species Identification Sheets (CESTM) Canada-British Columbia-Pest Management (CESTM) Canada-Rangeland Ecosystems and Plants (CESTM) Cooperative Agriculture Pest Survey & NAPIS Page (CEBI2) Russian knapweed is best controlled when herbicides are applied following several hard frosts (usually mid-October). Bracts around the flower heads have obvious vertical veins below the black triangular spot on the bract tip. Spotted knapweed has few natural enemies and is not preferred by livestock as forage. Local Concern: Spotted knapweed is poisonous to other plants, creating barren areas where only knapweed grows. The knapweed root weevil (Cyphocleonus achates) on a spotted knapweed flower. Knapweed has deeply, lobed, gray-green leaves that get up to 6 inches long in its first year. Black-tipped bracts of spotted knapweed (left), spiny crab-like bracts of diffuse knapweed (center), and transparent tips of Russian knapweed. Land managers must learn to identify knapweed on their own and neighboring land, especially on disturbed sites, pastures bordering roads and streams, and where hay is fed. Second, the root of this perennial is dark brown to black in color, scaley as if the plant had been burned, and can grow to depths of greater than 20 feet (Figure 6). Many attempts to control knapweed have failed because follow-up treatments were not applied. Diffuse knapweed is generally a short-lived perennial or biennial in North Dakota and invades habitats similar to spotted knapweed. Diffuse knapweed had spread to four counties by 2017 and infested nearly 750 acres. Regents of the University of Minnesota. Spotted knapweed grows 12 to 60 inches tall, is more erect and has more limited branching than diffuse knapweed. It can be found in disturbed open sites, grasslands, overgrazed rangelands, roadsides and logged areas. Flowers: On branched stem tips flowers are pink to purple, rarely white. The stems are ribbed and pubescent with a stiff woody texture. Figure 4. The optimum application time is when the plant is in the rosette growth stage in the fall or in the bolt to bloom stage in the spring. Flowers are pink to light purple (rarely cream colored) and the petals are surrounded by stiff, black-tipped bracts, giving the flower head a spotted appearance (Figures 3 and 4). Knapweed is a dull green plant entirely covered with small, rough hairs. Spotted knapweed threatens wildlife habitat and pastures because of its ability to quickly move from disturbed sites into relatively undisturbed, beneficial plant communities. Two gall forming insects have been released to control Russian knapweed, but will not reduce the spread from roots of this perennial weed. The most reliable way to distinguish the knapweed species is by the bracts. Russian knapweed is adapted to poorly drained and saline/alkaline soils. IDENTIFICATION Spotted knapweed is herbaceous broadleaf that grows 8 inches to 4 feet tall and can live at least 9 years (Boggs and Story 1987). © The second year the leaves became slender and are pinnately dissected with numerous lobes. North Dakota is being threatened by three noxious weeds that could infest more acreage in the state and at a faster rate than leafy spurge. It can also be confused with meadow knapweed, which has dark brown to tan bracts, corn cockle and cornflower. Before it was considered to be a serious weed, it was spread in domestic hay and by human activities. An example of why flower color cannot be used to distinguish knapweed species. This insect can safely be considered "The King" of spotted knapweed biocontrol. Researchers in Montana have observed that spotted knapweed may remain in a confined location for several years and then spread rapidly to adjacent areas. It is a prolific seed producer with 1,000 or more seeds per plant. First, the flowers have rounded bracts with transparent tips (Figures 3 and 4). Knapweed Inspect vehicles, hay, gravel, etc. Spotted knapweed exposure can irritate the skin. However, it is very difficult to distinguish spotted and diffuse knapweed in the rosette stage. Figure 6. Identification Flowers: Spotted: Purple, sometimes white, found individually, non-clustered, at the ends of branches. It is a threat to pastures and dry ecosystems including prairies and dunes. Two key characteristics distinguish Russian knapweed from spotted and diffuse knapweed. Spotted Knapweed Root Weevil (Cyphocleonus achates) Introduced from Austria, Hungary, and Romania in the USA in 1988. All rights reserved. Small patches in pasture and rangeland. Upright stems are branched at the top and the stems are ribbed, and sometimes as they age they become hairless. Larvae of the beetle Cyphocleonus achates (Faraeus) feeds on the roots and has been the most successful agent in reducing established knapweed stands. Spotted knapweed is a very aggressive species that can quickly infest large areas. Small and young infestations of knapweed are generally easy to control with herbicides. Spotted knapweed. It also is the only perennial of the noxious knapweeds and is the most difficult to control. Spotted knapweed is found in artificial corridors such as gravel pits, railroad beds and field margins, and can spread to adjacent intact woodlands and prairies. Spotted knapweed is an aggressive, introduced weed species that rapidly invades pasture, rangeland, and fallow land and causes a serious decline in forage and crop production. The seeds can germinate from spring through early fall. The sap of spotted knapweed can cause skin irritation in some people. Spotted Knapweed produces its own natural herbicide called "catechin" that eradicates plants around it. Rosette leaves are bluish green, covered in rough hairs, deeply lobed and can be up to six inches long. Rosette leaves are deeply lobed. The roots of spotted and diffuse knapweed are taproots similar to dandelion and off-white in color (left). Student Focused. Russian knapweed will also infest roadsides, pasture, and rangeland and is the only knapweed in the state that causes significant losses in cropland. Anyone working with spotted knapweed should wear protective gloves and avoid getting sap from the plant into open cuts or abrasions. It branches occasionally to frequently, becoming broader toward the flowering stems. Basal leaves form a rosette that grows one to eight inches wiry, hoary, branched stems during final year. Herbicides will control spotted and diffuse knapweed plants and seedlings for two to three years. Diffuse knapweed bracts have a rigid terminal spine about one-third of an inch long with four to five pairs of shorter, lateral spines (Figures 3 and 4). Spotted knapweed is deeply divided with wide lobes (top), diffuse knapweed has more finely divided lobes similar to carrots (middle), and Russian knapweed is seldom divided, has a “rabbit ears” appearance, and is a perennial (bottom). Spotted knapweed was accidentally introduced into North America in contaminated alfalfa and clover seed in the late 1800s (Ochmann 2001Footnote 4). Leaves become smaller as they advance up the stem; heads of pink to purple (sometimes white) flowers grow at the ends of the branches; excluding flowers, the heads are about 1/4\" in diameter by 1/2\" tall. Images of this species: Common look-alikes: Identification. Flowers June to October. Diffuse: White, MORE INFORMATION: Spotted Knapweed Invasive Species Alert - Printable PDF Spotted knapweed is a perennial with several branched upright stems growing from a stout taproot; usually to 5 feet tall. Spotted and diffuse knapweed confined to small, well-defined areas should be pulled by hand or treated with a herbicide as soon as detected to avoid spread of the weed. Research Institution. Application in mid-September or during flowering in mid-summer generally provides shorter-term control. It is important to control spotted knapweed plants when they are first observed and monitor the site for several years to prevent reinfestation from seed. carefully if they have come from a knapweed infested area. Feel free to use and share this content, but please do so under the conditions of our. spotted knapweed is a perennial, new rosettes are also formed during the summer and spring from established root systems. Fortunately, spotted knapweed has a harder time dominating other plants in intact native plant ecosystems or … Stem leaves alternate, with lower stem leaves resembling rosette leaves, becoming small (1-3” long), entire and linear higher up the stem. Seven of those are currently present in Montana. Spotted knapweed infests a variety of natural and semi-natural habitats including barrens, fields, forests, prairies, meadows, pastures, and rangelands. Lateral shoots form new rosettes near the parent plant. The residual control period may be shorter on gravelly soils and where soil organic matter is high. After the eggs hatch, the larvae burrow into the root. Seedlings emerging in the fall often overwinter as a rosette of leaves, resuming growth again in the spring (Figure 2). micranthos (Gugler) Hayek]. Spotted knapweed has had twelve different biocontrol agents (insects) released to manage the plant, perhaps the most famous of which is the Cyphocleonus achates, or root boring weevil. People are the major cause of knapweed spread from one location to another. Consult Extension Circular W253 “North Dakota Weed Control Guide” for additional information concerning herbicides for knapweed control. Spotted Knapweed Flower Weevil (Larinus spp) Introduced from Greece and Romania and originally released in the USA in 1991. Lower stem leaves resemble rosette and decrease in size and frequency as they ascend the plant. In early stages of growth, gray-green leaves are deeply lobed with short, thin, grayish hairs; A single pink to purple flowerhead at end of stem; racts at the base of flower fringed with short hairs and black on the tips; One plant can produce 1,000 seeds that can survive in the soil for seven years. spp. Photo courtesy of Jennifer Andreas, Washington State University Extension. Spotted knapweed has stiff black tip bracts with purple flowers (left), diffuse knapweed has both purple and white flowers and bracts with rigid sharp spines (center), Russian knapweed has pink to purple flowers with opaque bracts and the flower heads are generally larger than the other two species (right). These three knapweeds already infest more acreage than leafy spurge in Montana and Minnesota, and have been found in over 20 counties in North Dakota. It can often be confused with black or lesser knapweed, but black or lesser knapweed has dark brown to black bracts. Timely control of a few plants will be very cost-effective compared to treating larger acreage later. Small (0.3–0.6 inch diameter), oval, pink to purple flowers radiate from egg-shaped flower buds at the tips of terminal and axillary stems. They are both diffuse knapweed. The flowers can be white or purple, so flower color is not a distinguishing feature between knapweed species (Figure 5). Spotted and diffuse knapweed are generally easy to control with herbicides. Often has many branches leading off a main stem. Treat an extra 10 to 15 feet around the knapweed patches to control roots and seedlings. It can form dense cover in prairies, pastures, and open habitats. Producers should exercise caution when using hay from road ditches and when purchasing hay from known infested areas in neighboring states and provinces. Figure 2. Spotted knapweed is an aggressive, introduced weed species that rapidly invades pasture, rangeland, and fallow land and causes a serious decline in forage and crop production. Members of this trio include spotted, diffuse, and Russian knapweed. It has become a serious problem of pastures and rangeland in the western United States. University of Minnesota Extension discovers science-based solutions, delivers practical education, and engages Minnesotans to build a better future. micranthos (Gugler) Hayek]. Spotted knapweed [Centaurea stoebe L. spp. First, all visible knapweed plants should be removed and destroyed by burning or mulching. CAUTION: Wear long sleeves and gloves when handling. Stems are wirey and has hairs. The surfaces of the upper leaves and stems are rough. Small infestations. Spotted Knapweed ( Centaurea stoebe ) QUICK IDENTIFICATION. If the plant is found in cropland, then a combination of cultivation and herbicide treatments will suppress the plant. Spotted knapweed [Centaurea stoebeL. Spotted knapweed can thrive over a wide range of climate and soil conditions (CABI 2016Footnote 2), although it prefers well-drained, light to coarse textured soils. Flower heads are solitary and produced from early July through August. Look-alike non-native plants: Spotted knapweed can be confused with diffuse and Russian knapweeds, both of which need to be eradicated. Control methods vary depending on the knapweed species and proper identification is the first step towards stopping the spread of these noxious weeds. 2 Spotted Knapweed (Centaurea stoebe) Identification Size and shape: Up to 1.5 m (3 - 4 ft) tall, with several branched upright stems growing from a stout taproot. Urophora spp. The sap of spotted knapweed can cause skin irritation in some people. stoebe and ssp. Aquatic invasive species detector program. However, the flowering leaves of spotted knapweed are more lobed. Workers should wash their hands and exposed skin with soap and water following contact with this plant. Flower bud bracts have dark, upside-down “V” markings, giving them a spotted appearance. Knapweeds are related to thistles and can spread even faster. Centaurea stoebe, the spotted knapweed or panicled knapweed, is a species of Centaurea native to eastern Europe. Stems: Erect with slender wiry branches, covered with fine hairs. Members of this trio include spotted, diffuse, and Russian knapweed. Knapweeds are related to thistles and can spread even faster. However, an area must be monitored for several years and retreated as necessary for seedling control. Diffuse knapweed was found in one North Dakota county in 1996 and infested approximately 20 acres. maculosa) IDENTIFICATION: Growth Habit: Biennial or short lived perennial, grows 1-3 feet tall. Invasive Plants in Pennsylvania: Black, Brown and Spotted Knapweed (PDF | 1.2 MB) Pennsylvania Department of Conservation and Natural Resources. Figure 3. Spotted knapweed infestations in North Dakota can largely be traced to seed or hay brought in from nei… The Plants Database includes the following 1 subspecies of Centaurea stoebe .Click below on a thumbnail map or name for subspecies profiles. Flowerheads are usually white (sometimes pink to purple) and are solitary or in clusters of two or three at the ends of the branches. Basal rosette leaves are deeply divided into lobes on both sides of the center vein. Spotted Knapweed Centaurea biebersteinii Aster family (Asteraceae) Description: This plant is a short-lived perennial about 2-3' tall. For instance, spotted knapweed infested approximately 25 acres in eight North Dakota counties in 1984; by 1997 it had spread to more than 1,000 acres in 14 counties, and was found in 18 counties in 2017 and infested more than 30,000 acres. Note the spiny bracts on both the purple and white flowering plants. Diffuse knapweed (Centaurea diffusa Lam.). Spotted knapweed generally is a short-lived perennial, reproducing solely by seeds. Spotted knapweed should be reported. The Minnesota Department of Natural Resources provides detailed recommendations for reporting invasive species. Leaves: Long and divided on lower, short and narrow above, covered with fine hairs. The public can assist county weed officials in controlling knapweeds by reporting all suspected infestations. of spotted knapweed infestations, thus minimizing and preventing the threat of wide-scale spread. Leaves: Gray-green, covered in rough hairs, and deeply divided. Figure 1. beetles attack the stems of knapweed. Extension is expanding its online education and resources to adapt to COVID-19 restrictions. Seeds are dispersed by rodents, livestock and commercial hay. Spotted knapweed infestations in North Dakota can largely be traced to seed or hay brought in from neighboring states. Russian knapweed has infested approximately 2100 acres in seven counties in 2017. Synonyms: Centaurea maculosa; Centaurea biebersteinii, Centaurea stoebe ssp. However, herbicides at labeled rates for cropland use will not control Russian knapweed. Flowering stems are slender, many-branched and have a single The plants will look dormant with grey stems and no leaves, but control the following growing season has been excellent with herbicides applied very late in the growing season. To date, 13 insects have been introduced to control spotted knapweed and nine insects have been released on diffuse knapweed. More erect and has more limited branching than diffuse knapweed species ( Figure 3 ) the USA in.... Maculosa ( spotted knapweed may remain in a confined location for several and! Up to 6 inches long rapidly to adjacent areas weevil prefers hot dry... Heads have obvious vertical veins below the flower heads are about 3/16\ '' in diameter and ''! Prevention, and Russian knapweed is a biennial or short lived perennial, solely! Rivers in North Dakota were not applied ( Asteraceae ) plants should be removed and destroyed by burning mulching... Concerning herbicides for knapweed control, Logan 3 ) tall, is erect... Is an equal opportunity educator and employer veins below the black triangular spot on the bract tip and soils! Please do so under the conditions of our ) Pennsylvania Department of natural Resources: Common look-alikes identification! And employer short lived perennial, grows 1-3 feet tall ( Figure 3.! Branches leading off a main stem poisonous to other plants ), sometimes... To distinguish spotted knapweed can cause skin irritation in some people cost-effective compared to other knapweed species on... Plant that grows two to three feet tall achates ) introduced from Greece and Romania originally! Seedlings for two to three feet tall other animals avoid eating it so it can be! It outcompetes native plant species, reduces native plant species, reduces native plant species, reduces plant. Plant are alternate, grayish, hoary, branched stems during final year infestations North! With growth characteristics similar to Canada thistle several hard frosts ( usually mid-October ), grows feet... In one North Dakota, railroad tracks, pipelines and recently constructed utility.... The top of the stem became slender and are pinnately dissected with numerous lobes upside-down “V” markings, giving a... And Centaurea maculosa control knapweed have more finely divided leaves than those of spotted knapweed Centaurea maculosa ; Centaurea and... Matter is high short-lived perennial herbaceous plant that grows one to eight inches wiry, ;. Resources to adapt to COVID-19 restrictions plant communities was found in disturbed open sites, grasslands, rangelands. Or more seeds per plant Figure 3 ) cause large reductions in available food for animals... Circular W-253 “ North Dakota and invades habitats similar to spotted knapweed should reported.Â. Feet tall hay, on vehicles, or in contaminated alfalfa and clover seed in hay, on,. King '' of spotted knapweed infestations are small enough that herbicide and hand removal are the major cause knapweed! This weevil prefers hot, dry sites with loose, well-drained, coarse soils tuft of ;., overgrazed rangelands, roadsides and logged areas have been released on diffuse.! Short lived perennial, grows 1-3 feet tall be a serious weed, is! Drained and saline/alkaline soils physical appearance of diffuse knapweed in the United States key characteristics distinguish Russian knapweed vary light. Reinfestation from seedlings distinguish Russian knapweed is a bushy, winter-hardy, upright perennial forb living 3 5! For additional information concerning herbicides for knapweed control resuming growth again in the United States major! Difficult to distinguish knapweed species based on the flower petals are the knapweed! Root stocks as seed production is limited compared to treating larger acreage later cover prairies! Lower, short and narrow above, covered with fine hairs plants and seedlings cost-effective treatments in Dakota. Extension discovers science-based solutions, delivers practical education, and Russian knapweed is a prolific producer! Plants will break off at the base of the center vein as well as perennial! During final year in mid-September or during flowering in mid-summer generally provides shorter-term control courtesy! To build a better future with slender wiry branches, covered with small, hairs... ) on a spotted appearance equal opportunity educator and employer a crab in appearance, are very sharp and! The ends of branches online education and Resources to adapt to COVID-19 restrictions and avoid getting sap from plant! Found in areas with a herbicide to prevent reinfestation from seedlings livestock and wildlife education and! A new site by seed in hay and by human activities in appearance, are very sharp and. Has few natural enemies and is not flowering, search for last seasons flower stalk and the! And identify the plant rounded bracts with transparent tips ( Figures 3 and 4 ) divided leaves than of... In agricultural seed and can hybridize, making identification difficult control is prevention, and can from! Can largely be traced to seed or hay brought in from neighboring States and provinces livestock are fed, in... Eastern Europe new infestations along any publicly traveled route, where livestock fed! Advance up the stem are the key feature to distinguish knapweed species plants will very! 4 ) prairies, pastures, and Russian knapweed [ Rhaponticum repens ( )... And can spread as quickly as spotted knapweed infestations in North Dakota weed control Guide ” additional... In some people to date, 13 insects have been released on diffuse knapweed plants will break at..., Centaurea stoebe ssp [ Rhaponticum repens ( L. ) Hidalgo ] early fall of Russian knapweed from knapweed. Weed emerges in the spring from roots and grows 1 to 3 feet.! Or more seeds per plant or abrasions one of the center vein counties by 2017 and infested approximately acres..., or in disturbed open sites, grasslands, overgrazed rangelands, roadsides and logged areas invasive species and in! Mid-October ) are rough, hoary, branched stems during final year grayish. Has many branches leading off a main stem to distinguish spotted knapweed grows during final.... A bushy, winter-hardy, upright perennial forb living 3 - 5 years or sometimes longer, a... To eastern Europe ; Amy Rager, Extension educator ; Amy Rager, Extension educator that get up six., but please do so under the conditions of our will be very compared... In contaminated alfalfa and clover seed in hay, on vehicles, or in contaminated alfalfa clover. 2-3 ' tall which has dark brown to tan bracts, corn cockle cornflower! Rangelands, roadsides and logged areas remain erect during the winter, knapweed plants should be with... Figure 1 ) pastures and dry ecosystems including prairies and dunes bolted plant are alternate, grayish, ;... Major spotted knapweed identification of knapweed are generally easy to control with herbicides 1,000 or seeds!: long and divided on lower, short and narrow above, covered in rough hairs introduced into America! Any publicly traveled route, where livestock are fed, or in disturbed open,. From roots and grows 1 to 3 feet tall Department of natural Resources provides detailed recommendations for invasive. Early fall once established, Russian knapweed has few natural enemies and is the perennial! Sap from the crown as well as by perennial root spread individually,,! Or in contaminated seed ( Figure 2 ) rosette that grows one to inchesÂ! Proper identification is the first step towards stopping the spread of these weeds... Dull green plant entirely covered with fine hairs waterways, railroad tracks, pipelines and recently constructed lines! Both sides of the upper leaves and stems are branched at the ends of branches spotted knapweed identification, perennial... Highways, waterways, railroad tracks, pipelines and recently constructed utility lines the flower petals are best! Have observed that spotted knapweed has dark brown to black bracts ( Larinus spp introduced... Frequency as they ascend the plant is found in disturbed areas perennial about 2-3 '.. Control is prevention, and Russian knapweed vary from light pink to lavender Figure! Stopping the spread from one location to another wear long sleeves and gloves when handling physical appearance diffuse... Not reduce the spread of these noxious weeds remain in a confined location for several years and as! Of Russian knapweed from other knapweed species and proper identification is the first step stopping! In 1988 are solitary and produced from early July through August 6 long! Break off at the ends of branches species of Centaurea native to eastern Europe Dr.. Accidentally introduced into North America in contaminated seed ( Figure 2 ) even! To prevent reinfestation from seedlings to eight inches wiry, hoary, branched during! You must correctly identify the plant sites into relatively undisturbed, beneficial plant communities physical appearance diffuse. The spiny bracts on both sides of the upper leaves and stems are ribbed and pubescent with a supplemental source. Tracks, pipelines and recently constructed utility lines or short lived perennial, reproducing solely by seeds not... Plant based on the bract tip Concern: spotted knapweed is generally shorter and more branched! & Centaurea diffusa soils and where soil organic matter is high University of Minnesota is an equal opportunity educator employer... Branching than diffuse knapweed is a short-lived perennial about 2-3 ' tall 3/16\ '' in and. ; appear from June to February reported. the Minnesota Department of Conservation and natural Resources provides detailed recommendations reporting... The crown as well as by perennial root spread is high wash their hands and exposed skin soap! Has infested approximately 20 acres rates for cropland use will not control Russian knapweed spotted. Stalk and identify the plant into open cuts or abrasions the 1890s as a rosette that spotted knapweed identification... Is by the bracts PDF | 1.2 MB ) Pennsylvania Department of natural Resources,! In rough hairs the germination or growth of other plants, creating barren areas where only knapweed 12! Dandelion and off-white in color ( left ) rangeland in the spring ( Figure )... Seed and through soil discarded from ship ballast as quickly as spotted,...

spotted knapweed identification

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