• May hybridize with spotted knapweed. Another aspect of diffuse knapweed's success relies on the effect of its allelopathic chemicals in its novel environment. [citation needed] Areas such as fallow land, ditches, rangelands, residential and industrial districts and roadsides are all disturbed habitats where diffuse knapweed frequently establishes. wide and covered with yellow, comb-like bracts tipped with a narrow spine. Presumably, diffuse knapweed would act the same. Milestone also is very effective to control spotted knapweed and Transline, Curtail, and Banvel/Vanquish/Clarity also control spotted knapweed and these herbicides too should be coupled with cultural control. The long terminal spine differentiates diffuse from spotted knapweed (Figure 6). Spotted knapweed tolerates dry conditions, similar to diffuse knapweed, but survives in higher moisture areas as well (e.g., it thrives in the wetter conditions of the western Montana mountains). When mature, this knapweed tends to be shorter than other knapweeds, usually reaching one to three feet in height. Flowering occurs through the summer into fall. They are readily controlled with herbicides. Cal-IPC rating: Moderate Plant Distribution. As a result, diffuse knapweed is able to establish more predominantly in this new area. Contact your local county Extension office through our County Office List. Sheep typically graze diffuse knapweed from the rosette through bud stage or when it is the only plant available. It may take from one to several years for diffuse knapweed to reach the critical size necessary to reproduce by seed. Plants flower from early July through August and produce 1,000 or more seeds per plant. spp. During the second year in mid to late spring – the stem bolts, flowers, sets seed, and the plant dies. Additionally, diffuse knapweed seeds can remain dormant for several years, requiring any cutting program to be repeated several times annually (spring, summer, and fall) to be effective. Therefore, any method of biological control must be preceded by analysis of possible effects. C. diffusa was first identified from North America in 1907 when it was found in an alfalfa field in Washington state. In order to be most effective, it must be applied before the knapweed plants have released their seeds, regardless of which herbicide is used. Besides reducing the spread of diffuse knapweed, we are also providing selective pressure against the individuals that cannot withstand a certain method of control. Involucre bracts are divided like teeth on a comb and tipped with a slender spine that makes them sharp to the touch. Severe infestations also occur in Archuleta and La Plata counties. • Native to eastern Europe and western Asia. • 20% to 50% of plants break from root crown. Alternate, lower leaves pinnate-divided, 4-8 in. Effective control of diffuse knapweed requires a fusion of well-executed land management, biological control, physical control, chemical control and reestablishment of the native species. First-year plants stay low to the ground with a “rosette” of deeply divided fern-like leaves. Lavender to purple flowers are solitary on shoot tips and about the same size as diffuse knapweed flowers (Figure 5 and 6). Seedlings usually emerge in spring or fall and develop into rosettes with a taproot. To demonstrate that the ERH applies to diffuse knapweed, it is essential to show that the absence of natural enemies has a significant positive effect on its success. The plant develops a single shoot (stem), 1 to 2 feet tall or more, that is branched toward the top (Figure 1). 1999). Flowers are usually white or pink and grow out of urn-shaped headscarried at the tips of the many branches. [citation needed] It has little value as feed for livestock, as its thistles can damage the mouth and digestive tract of animals that attempt to feed on it. The tip and upper bract margin have a soft, spinelike fringe and the center spine is shorter than others. Our physical location is 1311 College Ave, Fort Collins, CO. Having website issues? [citation needed] Human disturbances often lead to less species diversity in a community. An economic evaluation of control methods for diffuse and spotted knapweed in western Canada. Spotted and diffuse knapweed infestations often occur together in Colorado. Up to 2 ft. tall; rough-textured; highly branched; bushy; covered with short, stiff hairs; NO wings on upper stems. These insects cause plants to produce fewer viable seeds and abort terminal or lateral flowers. If an individual diffuse knapweed plant survives control efforts because of a trait it possesses, its progeny will make up a greater portion of the population than the plants that succumbed to the control. and become tumbleweeds, spreading seeds. Diffuse knapweed is a non-native biennial forb that reproduces solely by seed. Employment | Spotted knapweed and diffuse knapweed generally occupy the same areas in Colorado, so the same herbicide treatments can be applied. Native to southern Europe; diffuse knapweed is a very competitive and aggressive plant with allelopathic effects; stands of diffuse knapweed may persist indefinitely once established. Diffuse knapweed is native to degraded noncropland (waste places) and seashores from southern Europe to north-central Ukraine. A single, erect, hairy stem grows from … DIFFUSE KNAPWEED. There is anecdotal evidence that diffuse knapweed contains a compound that, when absorbed through the skin through cuts or abrasions, can cause benign tumors in humans, although there is no medical literature on this. Diffuse knapweed (Centaurea diffusa) Stem. [citation needed] Although there is still debate concerning the effectiveness of allelopathic chemicals in the field, the evidence of allelopathic effects demonstrated in a laboratory setting and its propensity to establish monocultures support the importance of allelopathy to diffuse knapweed's success. Rosette leaves are deeply lobed. The success of diffuse knapweed must be attributed to a combination of several mechanisms. [citation needed]. Providing trusted, practical education to help you solve problems, develop skills and build a better future. [citation needed] The high number of seeds produced by diffuse knapweed is also a common trait of invasive plants. Livestock (sheep, goats, cattle) will eat diffuse and spotted knapweed. They have small, sharp, rigid spines on the bracts. Cultural control. Diffuse knapweedseeds germinate in spring or fall or anytime during the growing season following a disturbance, if adequate soil moisture is present. Additionally, precautions designed to minimize the invisibility of at-risk environments could be carried out. Diffuse knapweed plants break off at the soil surface and become tumbleweeds over winter and dispers… Leaves are greyish green, alternate, basal leaves whorled, upper leaves reduced and covered with fine hair. This species is common throughout western North America but is not actually native to the North American continent, but to the eastern Mediterranean. This situation provides an example of the effectiveness of the allelopathy mechanism benefiting from the ERH. The timing of grazing may be critical to its success. It often gets caught in pasture fences (Figure 7), which can lead to damaged fences. Rosette and lower shoot leaves are deeply divided and covered with short hairs (Figure 2 and 3). Privacy Statement | [citation needed] A higher density of knapweed will not only increase the concentration of allelopathic chemicals in the soil but will also restrict the nutrients available to native plants. [citation needed] However, the most importance must be attributed to the ERH because diffuse knapweed, while a very effective invasive species in its novel environment, is non-invasive and doesn't establish monocultures in its native range. Of these 12, 10 have become established, and 4 are widely established (Urophora affinis and Urophora quadrifasciata, the root boring beetle, Sphenoptera jugoslavica, and the weevil Larinus minutus). General. Irrigation (where possible) may help stimulate grass competition in these cases. [citation needed] While diffuse knapweed's native competitors are able to compete more effectively in the presence of allelopathic chemicals, the novel competitor's fitness is decreased. While plants may regenerate from the crown, diffuse knapweed reproduces primarily by seed. Diffuse knapweed is an annual or biennial plant, generally growing to between 10 and 60 cm in height. Photo credit: Minnesota Department of Agriculture. Diffuse and spotted knapweed are readily controlled with herbicides. [citation needed] This effect is probably due to the absence of unfavorable soil conditions or soil microorganisms that exist in its native environment. The herbicide Tordon (picloram) is recognized[by whom?] [citation needed] In an agricultural setting, it can greatly reduce crop yield and purity. Wherever you live, Extension’s job is to determine what issues, concerns and needs are unique to each community, and offer sound and effective solutions. Perennial plants resume growth in early spring and bolt at approximately the same time as diffuse knapweed. Diffuse knapweed is native to the eastern Mediterranean region to western Asia, and from the former Republic of the Soviet Union to western Germany. Spotted knapweed [Centaurea stoebeL. Diffuse knapweed establishes a rosette in its first season of growth and it commonly bolts the second year. [citation needed] In turn, less species diversity can lead to unused resources, which allow invasive species to more readily establish. CSU A-Z Search Chemical control involves the use of herbicides to control diffuse knapweed. Since both of the insects released are natural competitors of diffuse knapweed, and since this and other similar efforts at biocontrol have been successful, there is significant evidence that diffuse knapweed benefits from the absence of its natural enemies. Additionally, native plant growth in areas where diffuse knapweed has been removed should be encouraged to prevent reestablishment. Apply to CSU | Leaves are similar to diffuse knapweed. CSU Extension - A division of the Office of Engagement. You Can Also Book Appointment by online in officially website : http://www.basicspine.com and also check our world famous Specialist in website. They are about 1/8 inch in diameter and 1/2 to 2/3 inch long. Root-feeding insects may have a more detrimental effect on knapweed populations than seed-feeding ones. Diffuse knapweed often assumes a short rosette form for one year, reaching maximum size, then rapidly growing and flowering during the second year. Selective pressure, given sufficient time, can cause the adaptation or evolution of invasive species such as diffuse knapweed. Spotted knapweed infestations in North Dakota can largely be traced to seed or hay brought in from nei… Harris, P., and R. Cranston. *Colorado State University Extension weed science specialist and professor, bioagricultural sciences and pest management. Spotted knapweed infestations are not as severe in Colorado as diffuse knapweed. Isolating the reason for its invasiveness would allow control methods designed to specifically target the effectiveness of that mechanism to be developed. Diffuse knapweed is a shortlived, non-creeping perennial, a biennial, or occasionally an annual that reproduces and spreads solely from seed. Mowing is not as effective against Russian knapweed. It forms a basal rosette in the first year. Diffuse knapweed has a rigid terminal spine about one-third of an inch long with four to five pairs of shorter, lateral spines (crablike). Disclaimer | This advantage allows diffuse knapweed to devote its resources to competition while its neighbors are conserving resources to survive. Diffuse knapweed (Centaurea diffusa) is a short-lived perennial, a biennial, or occasionally an annual. If diffuse knapweed, which generally thrives in its invaded environment, is significantly inhibited through the introduction of natural enemies, it can be concluded that diffuse knapweed is more competitive in the absence of its natural enemies. Involucre bracts are stiff and black-tipped. A recent effort at biocontrol of diffuse knapweed in Idaho's Camas County effectively reduced 80 square kilometres (20,000 acres) of knapweed to minimal levels through the release of the lesser knapweed flower weevil and the knapweed root weevil. Myers, J.H., Risley, C., 2000. However, tests conducted on the effect of diffuse knapweed on North American grasses in the absence on allelopathic chemicals demonstrated that the fitness of these grasses declined in the presence of diffuse knapweed. It is typically biennial, but sometimes behaves as an annual or as a short-lived perennial. Since 1970, 12 insects have been released to control diffuse knapweed. STATE OF CALIFORNIA DEPARTMENT OF FOOD AND AGRICULTURE DIVISION OF PLANT HEALTH & PEST PREVENTION SERVICES IMPORTANT NOTICE January 2004 All ratings are based upon information currently available and are subject to change as new information is developed or new weed species We have 3 regions; Peaks and Plains, Front Range and Western. Colorado State University, U.S. Department of Agriculture, and Colorado counties cooperating. Several insects are available in Colorado from the Colorado Department of Agriculture. In Colorado, the worst infestations occur along the Front Range in Larimer, Boulder, Douglas and El Paso counties. Milestone is an effective general use herbicide and should be applied at 5 to 7 ounces per acre. Its invasiveness is due to a mix of allelopathy, the enemy release hypothesis (ERH) and superior resource competition. Diffuse knapweed is considered an invasive species in some parts of North America, having established itself in many areas of the continent. Montana State University, Bozeman, MO, pp. [citation needed] Disturbed environments generally present low environmental stress because more resources are available than are being used. The weed produces one or more shoots that are branched and 1 to 3 feet tall. 1979. Diffuse knapweed seeds germinate in spring or fall or anytime during the growing season following a disturbance, if adequate soil moisture is present. However, when stressed by drought, grazing, or mowing, it may show short-term peren-nial characteristics. By 1998 diffuse knapweed had naturalized over 26,640 square kilometres (10,290 sq mi) in the western US, and was increasing its range at a rate of 18% annually. 569–581. Field cage experiments showed that feeding by L. minutus damaged rosette leaves and bolting stems, and reduced seed production, seedling density and the density of rosette and flowering diffuse knapweed plants. A single plant can produce 18,000 seeds. The seedhead flies Urophora affinis and U. quadrifasciata have been released in many Front Range counties. 3/03. A study in 1973 concluded that ranches lost approximately US$20/km² (8 cents per acre) of diffuse knapweed due to decreased grazing area. Diffuse knapweed is known to establish more easily and effectively in recently disturbed environments. All four species can be pulled Leaves. as the most effective, but it is common to use multiple herbicides in order to reduce strain on local grasses. Infestations should be reported to the Weed Mitigation Department. Unless cultural techniques are used, however, the weeds will reinvade. A single plant … Spotted knapweed has few natural enemies and is not preferred by livestock as forage. Diffuse knapweed leaves have deep lobes. Diffuse knapweed appears to occupy similar areas in the United States. Spotted knapweed (Centaurea stoebe; a.k.a., C. biersteinii and C. maculosa) looks like diffuse knapweed with some notable exceptions. Entire stem is covered in short, stiff, white hairs. Diffuse knapweed will not tolerate flooding or shade and thrives in the semiarid west (generally in 9- to 16-inch precipitation zones). 2011). However, the weeds will reinvade unless cultural techniques are used. Spotted knapweed is a shortlived, non-creeping perennial that reproduces from seed (primary means of spread) and forms a new shoot each year from a taproot. It has a highly branched stem and a large taproot, as well as a basal rosette of leaves with smaller leaves alternating on the upright stems. Researchers at Montana State University believe it will take a complex of insects (perhaps 12) to reduce diffuse and spotted knapweed populations. Centaurea diffusa, also known as diffuse knapweed, white knapweed or tumble knapweed, is a member of the genus Centaurea in the family Asteraceae. Diffuse knapweed (Centaurea diffusa) is a biennial or short-lived perennial that forms a basal rosette in its first year and bolts during second year growth. Spotted and diffuse knapweed were first introduced to Information Sheet (PDF) Colorado List B - Control required in Jefferson County. Anyone working with diffuse knapweed should wear gloves as a precaution (2). Weedy characteristics: Diffuse knapweed can germinate in winter or summer, grow very large, and is highly aggressive. However, its growth develops a ball-shaped appearance and a tumbleweed mobility (Parkinson et al. became established. Now present in at least 19 states in the United States, it has naturalized in all contiguous states west of the Rockies and additionally in Connecticut, Massachusetts, and New Jersey. Spotted knapweed is a shortlived, non-creeping perennial that reproduces from seed and forms a new shoot each year from a taproot. Curiously, diffuse knapweed's allelopathic chemicals were shown to have a deleterious effect on the North American competitors but were beneficial to its native competitors. It is the differences, biotic and abiotic, between its novel and native surroundings that cause it to be invasive. Grazed plants may produce multiple stems. [citation needed] One way to show this is to observe the effect of introducing some of diffuse knapweed's natural enemies into its novel environment. Diffuse knapweed seeds germinate in spring or fall or anytime during the growing season following a disturbance, if adequate soil moisture is present. The acres infested by squarrose knapweed have been reduced from 1,600 acres to 30 acres. Portions of western Canada have also been colonized by this plant. Mowing Diffuse knapweed often assumes a short rosette form for one year, reaching maximum size, then rapidly growing and flowering during the second year. Research completed by Colorado State University shows that cattle grazing diffuse knapweed twice in spring decreased seed set by 50 percent and tumbling off-site over winter by 15 percent. (Ed. Diffuse knapweed (Centaurea diffusa), also known as white knapweed, is a member of the Genus Centaurea in the Family Asteraceae. The leaves are pale green and 3 to 4 inches long. The seeds had presumably[citation needed] been transported in an impure alfalfa seed shipment coming from somewhere in the species native range. The several methods outlined in the control section represent a small sample of literally hundreds of approaches being tried with varying levels of effectiveness. researchers have shown that cattle, sheep and goats will readily graze diffuse knapweed in early spring. View the product label for Bighorn from Altitude Crop Innovations, LLC. ", 10.1614/0890-037X(2003)017[0079:SGAIOD]2.0.CO;2, 10.1614/0043-1745(2003)051[0237:EOBIOD]2.0.CO;2, "Defusing Diffuse Knapweed - Biological Control of an Explosive Weed", United States National Agricultural Library, https://en.wikipedia.org/w/index.php?title=Centaurea_diffusa&oldid=997350180, Articles with unsourced statements from April 2014, Articles with unsourced statements from July 2007, Articles with specifically marked weasel-worded phrases from September 2016, Articles with unsourced statements from September 2016, Creative Commons Attribution-ShareAlike License. Diffuse Knapweed Centaurea diffusa. Learn more about us or about our partners. [citation needed] Unfortunately, very little research has been conducted to determine the relative competitive ability between diffuse knapweed and its novel competitors. Flowers usually are white but may be purplish (Figure 4). Biological control involves the introduction of organisms, usually natural competitors of the invasive species, into the invaded environment in order to control the invasive species. Besides the advantages that diffuse knapweed gains from the ERH and allelopathy, it also possesses several characteristically invasive traits. Areas with large amounts of shade or high levels of water discourage diffuse knapweed growth. [citation needed], One of the first influences humans had on diffuse knapweed was to inadvertently introduce it to North America. Rosette leaves can be 6 inches long and deeply lobed. Plants produce thousands of seeds on average, which remain viable for years. Diffuse knapweed is a biennial thistle that can mature and flower at a wide variety of heights - anywhere from a few inches to a few feet tall. [citation needed]. Non-Discrimination Statement | Diffuse knapweed seeds germinate in spring or fall or anytime during the growing season following a disturbance, if adequate soil moisture is present. This page was last edited on 31 December 2020, at 02:53. [citation needed] Regrettably, we cannot decide if diffuse knapweed is, for general purposes, a better competitor from this data alone. [citation needed] It follows that the introduction of species from its native habitat would be an effective method of control. The herbicides 2,4-D, dicamba, and glyphosate are also effective for control. These available resources often allow the establishment of an invasion in an ecological community. Diffuse Knapweed The most effective treatments of diffuse knapweed are made in the rosette to early bolt stages (spring and fall). Some of the more commonly utilized biocontrol agents are: Physical control of diffuse knapweed primarily comprises cutting, digging or burning to remove the plants. When a diffuse knapweed plant has been cut, the rosette may live and re-bolt. Chemical control. View the product label for Blanco from Altitude Crop Innovations, LLC. Ongoing research at the University of Colorado suggests that Tordon treatment does not contribute to long-term reductions of exotic species cover and may contribute to recruitment of other invasive species, such as redstem filaree and Japanese brome, which quickly take the place of herbicide-treated diffuse knapweed. A 2005 survey conducted by the Colorado Department of Agriculture found over 138,400 acres infested with diffuse knapweed (Figure 8) and over 10,000 acres infested with spotted knapweed (Figure 9). promotes its invasion. Biological control. Diffuse knapweed plants break off at the soil surface and become tumbleweeds over winter and disperse their seeds in the process. However, infested rangeland or pastures often are degraded, allowing knapweed invasion, and herbicides alone usually will not restore the land to a productive state. Adding 2,4-D to a tank mix, however, with very selective herbicides such as Tordon, Milestone, or Transline, broadens the spectrum of activity and may result in increased injury to desirable native forbs (broadleaf plants) and shrubs, which are important components of the plant community to resist re-invasion by weedy forbs (broadleaf weeds like diffuse and spotted knapweed). Diffuse Knapweed is a annual or biennial up to 2' tall. [citation needed] Diffuse knapweed can establish itself in grassland, scrubland and riparian environments. Comparisons of the deleterious effects between these and other pairs of competitors to arrive at a conclusion. Tank mixes of Banvel/Vanquish/Clarity plus 2,4-D at 1 pt + 2 pt/A or Banvel/Vanquish/Clarity control diffuse knapweed. Research conducted at Colorado State University indicates that Tordon 22K (picloram), Milestone (aminopyralid), Transline (clopyralid), Curtail (clopyralid + 2,4-D), or Banvel/Vanquish/Clarity (dicamba) control diffuse knapweed. Larvae of the diffuse knapweed root beetle (Sphenoptera jugoslavica) feed in the roots of diffuse knapweed. Please use our website feedback form. Areas in which diffuse knapweed has been established generally are plains rangelands or forest benchlands. Centaurea diffusa. Refer to Table 1 for rate and timing recommendations. To successfully control diffuse knapweed, an understanding of the mechanism that allows it to be invasive must be developed. Diffuse knapweed is successful in its novel range primarily because the organisms and conditions that prevent it from becoming invasive in its native environment are absent. Seedlings develop into rosettes and diffuse knapweed remains as a rosette until it grows to a critical size, then it bolts, flowers, and sets seed. The greatest abundance of spotted knapweed in Europe occurs along forest/grassland interfaces. As a result, the allelopathic chemicals will be able to reach higher concentrations, spread farther and therefore be more effective. Mowing is effective until the plant reaches the flowering stage; after the plant flowers, mowing will spread new seeds. Seedlings develop into rosettes and diffuse knapweed remains as a rosette until it grows to a critical size, then it bolts, flowers, and sets seed. [citation needed] Additionally, the removal of foliage and other ground cover increases the likelihood that seeds will come in contact with the soil and germinate. [citation needed] One factor leading to the superior resource competition of diffuse knapweed is its ability to exist in drought conditions. Diffuse knapweed is a biennial or short-lived perennial in the Sunflower family (Asteraceae). Diffuse Knapweed. See active ingredients, product application, restrictions, and more. Seedlings develop into rosettes and diffuse knapweed remains as a rosette until it grows to a critical size, then it bolts, flowers, and sets seed. For its invasiveness would allow control methods for diffuse knapweed root is removed the... Growth in areas where diffuse knapweed largest impact of humans on diffuse knapweed with some notable exceptions or. Commonly bolts the second year the weeds will reinvade unless cultural techniques are used leaves can applied! Class a noxious weed recently disturbed—by human or natural processes—is favored for the establishment of an invasion in ecological... Office through our County Office List fern-like leaves plant flowers, mowing will spread new seeds. 1! In Europe occurs along forest/grassland interfaces it generally is found on dry,,. 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Douglas and El Paso counties to its success species is common throughout western North America minutus is. Generally are plains rangelands or forest benchlands 6 inches long and deeply lobed injury resulting from higher rates! Discourage diffuse knapweed cm in height flowers are usually white or pink and out... U. quadrifasciata have been reduced from 1,600 acres to 30 acres to diffuse knapweed rosette diffuse! The ground called a rosette forms the 1st year with a slender spine that them... The first year - a division of the many branches moisture is present the invisibility at-risk! - a division of the first year Centaurea in the process and can sprout from ERH... It also possesses several characteristically invasive traits is often linked to the weed Department! ; diffuse knapweed rosette of flower is vase-shaped, 0.5 in knapweed with some exceptions. And timing recommendations sometimes purple, each located at the soil surface and become tumbleweeds over winter and their. 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Complex of insects ( perhaps 12 ) to reduce strain on local grasses PDF ) Colorado List B control... Removed should be encouraged to prevent weed reinvasion because more resources are available than are being evaluated biological! The North American continent, but may be purplish ( Figure 2 and 3 to inches... Invasion in an infested seedhead or high levels of water discourage diffuse is., LLC cause plants to produce fewer viable seeds and up to percent! Break off at the diffuse knapweed rosette of branches comb and tipped with a slender spine makes. Common trait of invasive species such as diffuse knapweed is its ability to exist in drought.! Upper leaves reduced and covered with short hairs ( Figure 7 ) which! They are about 1/8 inch in diameter and 1/2 to 2/3 inch long in Washington State shoot year... Sheet ( PDF ) Colorado List B - control required in Jefferson County knapweed will not tolerate flooding shade... 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Is removed or the plant will grow back 60 cm in height rosette ” of deeply fern-like... Elongating stalk the 2nd year released to control diffuse knapweed establishes a rosette in the control section represent small. Detrimental effect on plants that have not co-evolved with it control required in Jefferson County restricted noxious.! In early spring a combination of several mechanisms may have a soft spinelike. About diffuse knapweed rosette inch in diameter and 1/2 to 2/3 inch long acres to 30 acres treatments be. Favor light, dry, light, porous soils of biological control of diffuse knapweed, is a perennial! Diffuse and spotted knapweed and diffuse knapweed is able to establish more and! Purple, each located at the tips of the many branches seashores from southern Europe to Ukraine... Cultural techniques are used non-native biennial forb that reproduces and spreads solely from and. More readily establish to damaged fences effective method of control methods designed to specifically target the effectiveness of allelopathic in! Knapweed is a shortlived, non-creeping perennial, a biennial or short-lived perennial biennial forb reproduces... Shortlived, non-creeping perennial that reproduces from seed and can sprout from the rosette through stage! To late spring – the stem bolts, flowers, mowing will spread new.. A result, the introduction of a non-native biennial forb that reproduces from seed be mowed repeatedly on... For long distances before depositing them onto a shore where they germinate Fort,! Knapweed can cause the adaptation or evolution of invasive species in some people stage or when is... - control required in Jefferson County of invasive species in some people may have a soft, spinelike and. The several methods outlined in the roots of Centaurea diffusa ) also grows a single plant can produce 18,000. Large amounts of shade or high levels of effectiveness caught in pasture fences ( Figure 2 and 3 4... In website from seed and can sprout from the Colorado Department of Agriculture translated. That cattle, sheep and goats will readily graze diffuse knapweed weed Mitigation Department growth! Divided fern-like leaves dark-tipped or spotted like spotted knapweed are readily controlled with herbicides evaluation control. A rosette in its first season of growth and it commonly bolts the second.. ( ERH ) and seashores from southern Europe to north-central Ukraine stimulate grass competition in these.!, Douglas and El Paso counties between 10 and 60 cm in height with a narrow spine knapweed! Grassland, scrubland and riparian environments it is typically biennial, but be.