Botanical description: This description covers characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (e.g., [30,32,39,84,89]). Many keys describe characteristics used to distinguish Fuller's teasel and cutleaf teasel [3,30,32,84,89,91].
Aboveground description: Fuller's teasel and cutleaf teasel are robust, prickly, monocarpic perennials that can reach 7 to 10 feet (2-3 m) tall [32,48,64,89]. Stems are erect, hollow, and support erect branches [69,89]. Degree of branching may relate to soil fertility. On "poor", rocky soils, branching may be limited . Teasel plants typically flower after 2 or more years of growth and die after flowering. The only Fuller's teasel plants to flower in their first year of growth were sown very early in the spring and grew in "well manured soil" (De Vries 1899 as cited in ). Plants grow as a rosette before bolting and flowering. Basal leaves generally die by the middle of the flowering season [18,31,32]. Teasel flowering and life span are discussed more in Flower and seed production and Seedling establishment and plant growth.
Teasel flowers occur in terminal, stiff, egg-shaped heads that are up to 4 inches (10 cm) long [32,52]. Inflorescences contain 250 to 1,500 flowers , which bloom for only 1 day . Flowering begins in the middle of the inflorescence and then progress up and down [32,91]. Often there are few flowers blooming at the same time . Flower heads are subtended by linear bracts that are about 4 times as long as they are wide . Teasel fruits are hairy achenes that measure up to 8 mm long [30,32,39,89].
Common and cutleaf teasel are distinguished by flower color and leaf morphology. Although both species have opposite, stem-clasping leaves, Fuller's teasel leaves are entire with toothed or wavy margins and cutleaf teasel leaves are pinnatifid. Fuller's teasel typically produces lavender flowers, while cut-leaved teasel flowers are generally white [3,33,76].
The cups formed by clasping leaves may be up to 5 inches (13 cm) deep . Although these cups collect water, they are not considered a carnivorous adaptation, but the water-collecting leaf arrangement and leaf and stem bristles may protect teasel from injurious or "nectar-thieving" insects .
Fuller's teasel leaves
Belowground description: Teasel produces a "stout" taproot [18,40,46]. Most detailed descriptions about root systems are specific to Fuller's teasel but may also describe those of cutleaf teasel. Fuller's teasel taproots may be more than 2 feet (0.6 m) long and 1 inch (2.5 cm) in diameter at the crown [22,95]. Jurica  indicated that Fuller's teasel taproots support many branching rootlets. While most report a deep taproot, Uva and others  described a shallow taproot with a fibrous secondary root system for Fuller's teasel.
In North America, Fuller's teasel and cutleaf teasel are nonnative. Both the native and nonnative ranges of Fuller's teasel are more extensive than those of cutleaf teasel. Fuller's teasel is native to Europe, temperate Asia, and northern Africa, and cutleaf teasel is native to Europe and temperate Asia . Fuller's teasel occurs throughout most of the United States except the northern Great Plains and several southeastern states [22,86,87]. Cut-leaved teasel is most common in the northeastern and Midwestern United States , although it was reported near Denver, Colorado , and in Oregon . Fuller's teasel is generally more common than cutleaf teasel, but throughout their ranges they are described as occasional, locally common, scattered, or infrequent [18,32,40,48,63,89].
Introduction(s) in North America: A review reports that Fuller's teasel was introduced in North America as early as the 1700s . No other references reported cultivation or collection of teasel in the 18th century. Cultivation of teasel occurred by 1840 in Onondaga County, New York, and by 1907 in Clackamas County, Oregon . Fuller's teasel was collected in Michigan in 1844  and Niagara Falls, Ontario, in 1877 . Cut-leaved teasel was reported in New York before 1900 and in Michigan as early as 1894 . NatureServe provides distributional maps of Fuller's teasel and cutleaf teasel.
Local distribution changes: In the northeastern United States, cutleaf teasel was present before the 1900s, but it spread more slowly or experienced a longer lag time than Fuller's teasel. Fuller's teasel was widespread in the northeastern United States by 1913, but at that time, cutleaf teasel was known only from New York . Fuller's teasel occurred in northeastern Tennessee as of 1956 and was described as "rather abundant in some places" . By 1945, Fuller's teasel occurred in Kansas , although populations were not reported from Texas until 2000 . Not until 1973 was cutleaf teasel collected in West Virginia .
In the western United States, Fuller's teasel occurred in northern Oregon and southern Washington by 1900. Populations spread east and occurred in Idaho and Montana by 1940 and Wyoming by 1980 [24,25]. Fuller's teasel was likely introduced in Portland, Oregon, an important shipping port .
Dispersal along roads and waterways has been important to teasel spread in North America [19,95]. On the Lincoln National Forest in central New Mexico, all Fuller's teasel populations in habitats occupied by the threatened endemic, Sacramento Mountain thistle (Cirsium vinaceum), occurred adjacent to roads (P<0.0001) . In Missouri, teasel populations have "skyrocketed" since the early 1990s. Populations have spread primarily along highways, and researchers suggest that right-of-way mowing operations have been important to seed spread . Since about 1965, cutleaf teasel spread from New York throughout the Midwest, and much of this spread has occurred along major roadways . By about 1980, cutleaf teasel was rapidly spreading throughout the Midwest [80,89]. In Illinois, areas with no or few cutleaf teasel plants supported large populations in 5 to 10 years (Solecki personal observation as cited in ). Cut-leaved teasel was first reported in Missouri in 1980, and by about 1990, occurred in 24 Missouri counties. Populations were most common along Interstate 70 .
Potential for postfire establishment and spread: Although information about fire in teasel habitats is lacking, managers could expect teasel to sprout following fire . Teasel germination levels could be high on open, burned areas, and given some protection by sprouting vegetation, teasel seedling establishment could be high. In the Loda Cemetery Prairie where spring fires occurred biennially and cutleaf teasel stems were cut annually, there were up to 1,926 seedlings/3 m² plots in the first or second postfire season . Teasel is dispersed by a variety of vectors (see Seed dispersal). Burned sites in the vicinity of established teasel populations should be monitored for seedling establishment, and appropriate control measures should be taken.
Use of prescribed fire as a control agent: While fire alone is unlikely to control dense teasel populations, it may be useful in conjunction with other control methods. Some suggest that periodic spring or fall fires may help control teasel populations [29,81]. Solecki  suggested that late-spring prescribed fires may control sparse teasel populations. The method by which fire provides teasel control was not described. It was unclear whether or not fire killed some teasel plants, consumed teasel seed, or improved conditions for more desirable prairie species. While "burning alone will not eradicate (teasel) populations" , fires may expose teasel rosettes, potentially increasing the effectiveness of other treatments .
Burning areas where teasel was cut should limit seed production and dispersal . Cut-leaved teasel seeds matured on and germinated from stems cut in Illinois. Stems were cut before any mature seed production, and after 1 month of storage at room temperature, 41% of seeds from cut stems germinated; after 7 months of storage, 97% germinated . Because viable seed can be produced on cut stems and seed may be shed during the transport of flowering or fruiting stems from an invaded site, fire may be useful in disposing of cut teasel stems.Several studies indicate that burning may be difficult in teasel habitats. In dense stands of teasel rosettes or mature plants, fire does not spread well [22,79]. In moist habitats where teasel is common, fire spread and temperatures lethal to plant tissue are rare. Prescribed fire may be impossible along high-traffic roadside habitats, which are important to teasel spread .
Teasel rosettes must reach a critical size before plants will produce flowers . In abandoned fields, Fuller's teasel rosettes that reached 20 inches (51 cm) in diameter in their 1st year flowered in their 2nd year. Teasel plants may produce over 3,000 seeds [79,95]. Loss of seed to birds and small mammals has been reported in several of Fuller's teasel's nonnative habitats [50,62,68].
Rosette diameter is highly significant in predicting the probability of Fuller's teasel flowering (P<0.001). In southwestern Michigan old fields, rosettes that were just 2 inches (5 cm) in diameter had a 65% probability of remaining vegetative and about a 30% chance of dying in the next growing season. Rosettes that reached 12 inches (30 cm) in diameter were 80% or more likely to flower in the next season .Probability of Fuller's teasel dying, remaining vegetative, or flowering based on rosette diameter in the previous growing season  Rosette diameter in August of previous year (cm) Probability of death Probability of remaining vegetative in the next growing season Probability of flowering in the next growing season <2.5 0.81 0.19 0 2.5-7.4 0.33 0.67 0 7.5-12.4 0.19 0.82 0.01 12.5-18.9 0.15 0.86 0.02 19.0-24.9 0.08 0.66 0.32 25-37.9 0.10 0.29 0.80 38-50.9 0.04 0.20 0.86 >51.0 0 0 1.00
In Michigan, Fuller's teasel plants produced an average of 854.6 seeds per flower head. Typically, 3 to 9 flower heads were produced per plant, although 1 to 35 flower heads were observed. In Michigan roadside populations, Fuller's teasel produced an average of 3.9 flower heads/plant and an estimated 3,333 seeds/plant . Assuming that cutleaf teasel seed production and field germination (28%-86%) approximated those reported for Fuller's teasel , a single cutleaf teasel plant could produce 716 to 2,292 new plants . Four years after introducing Fuller's teasel seed into old fields in Michigan, Fuller's teasel seed production was about 4,500 seeds/m² regardless of plant ages or flowering plant densities .
Several bird and small mammal species are potential teasel seed predators. Northern bobwhites, California quail , ring-necked pheasants , white-winged crossbills , goldfinches (Ridley 1930 as cited in ), and blackbirds (Pohl and Sylwester 1963 as cited in ) feed on Fuller's teasel seed. In a perennial grass and forb dominated field in southwestern Michigan, an average of 1% of Fuller's teasel seeds were removed daily . Based on the appearance of husks left behind, Mittelbach (personal observation as cited in ) suspected that mice were the seed predators.
Mature teasel seed may germinate immediately , but dormancy may be induced by freezing temperatures . Seeds may germinate at high levels in both the laboratory [34,98] and the field . Typically seeds germinate equally well in dark or light conditions . Seed size, litter cover, vegetation cover, and soil disturbances may affect germination, and environments that foster high seed germination percents may not be conducive to seedling growth and survival. For details about the conditions that foster germination, seedling establishment, and/or seedling survival, see the Case study on Fuller's teasel development and survival. For information about predominant germination times, see Seasonal Development.
Temperature and light: Warm temperatures, regardless of light conditions, produce high Fuller's teasel germination in the laboratory. Fuller's teasel seeds collected in the fall from a field on the Michigan State University campus averaged 99.6% germination without prechilling; 95% of the seeds germinated within 3 days. Seeds kept in the dark at room temperature averaged 95.5% germination. Seeds stored for 2 years in laboratory averaged 96% germination . Fuller's teasel seeds failed to germinate at temperatures below 32 °F (0 °C) . After a hard freeze in Michigan and Ohio, Fuller's teasel seed germination was 5.6% to 28% in the light and 0% in the dark in the laboratory. The next fall, 96% to 100% of Fuller's teasel seeds collected before freezing germinated, regardless of light or dark conditions . Fuller's teasel seeds collected in August from New Mexico's Lincoln National Forest germinated best (54%) at 72 °F (22 °C) with light. Germination was lower at 50 °F (10 °C) and 86 °F (30 °C). Seeds were refrigerated for about 5 months prior to testing germination .
Seed size: Large Fuller's teasel seeds germinate best. In a greenhouse study, germination of large-sized Fuller's teasel seeds was significantly greater than that of small- or medium-sized seeds (P<0.05). At least 70% of large-sized seeds (average 2.01 mg) germinated. Germination of small- and medium-sized seeds (average 1.12 and 1.73 mg, respectively) was less than 20% . Germination and initial seedling growth of Fuller's teasel from old field and roadside populations in Ontario, Canada, were positively associated with seed mass. The researcher suggested that "maternal provisioning" within a population may affect germination and seedling establishment .
Disturbances, litter, and established vegetation: Soil disturbances may cause flushes of teasel germination, whereas litter and established vegetation may inhibit teasel germination but foster seedling growth and survival.
During a field study in southern Warwickshire, England, flushes of Fuller's teasel germination occurred when the soil of buried containers was mixed to simulate soil disturbance . In a 6-year-old field in Michigan, there were germination flushes when litter was removed after planting Fuller's teasel seeds, but germination was much greater when litter was removed prior to seed planting. Just 1.2 out of 150 seeds germinated after 2 years on plots with litter. In the greenhouse, Fuller's teasel germination was least successful for seeds under quackgrass litter (Elymus repens), but seedling survival was greatest in quackgrass litter .Fuller's teasel seed germination and seedling survival in different depths and types of litter  Seed environment Average number of seeds germinating out of 50 seeds planted Seedling mortality after 3 weeks Uncovered 45.2a 1.7% Under 0.5 cm of vermiculite 44.8a 3.8% Under 1.5 cm of forb litter 41.8a 15.4% Under 2.8 cm of quackgrass litter 38.2b 0.1% Values followed by different letters are significantly different (P<0.05).
In another greenhouse study, Fuller's teasel germination was reduced by thick (715 g/m²) Kentucky bluegrass (Poa pratensis) litter, but a greater number of seedlings developed (92%) with a thin litter layer (123 g/m²) than without (58%) (P<0.05). Fuller's teasel seed germination was not significantly affected by 123 g/m² of Kentucky bluegrass litter, but 715 g/m² of Kentucky bluegrass litter decreased germination by 34% to 41%. Additional experiments showed that Kentucky bluegrass leachate may inhibit Fuller's teasel germination. About 34% more Fuller's teasel seeds germinated when kept moist with water than when kept moist with Kentucky bluegrass leachate [10,11].
Teasel is frequent on roadsides and ditches and in pastures, old fields, meadows, riparian areas, savannas, and forest edges [3,32,37,39,40,89]. Teasel occurs in various habitat and soil types. In the John Day River Basin of eastern Oregon, Fuller's teasel was abundant in big sagebrush/western juniper/cheatgrass-bluebunch wheatgrass vegetation on dry, low-elevation sites. Canopy gaps are common in this vegetation type . Along the James River in the central Blue Ridge Mountains of Virginia, Fuller's teasel occurred on floodplains that experienced frequent overflows and erosion . Climate and soil conditions in cutleaf teasel habitats were rarely described in detail. Based on the similarities between Fuller's teasel's long-occupied habitats and cutleaf teasel's newly occupied habitats, differences in environmental tolerances between the 2 species are likely subtle or disappearing over time.
Climate: Prevailing climates in teasel habitats were rarely described. In a review, Werner  reported that Fuller's teasel's northernmost North American distribution is generally that region where less than 1% of the minimum daily temperatures fall below 32 °F (0° C) in May and 50 °F (10° C) in July. Some suggest that Fuller's teasel grows best in areas receiving summer moisture (Clapham and others 1962 as cited in ). Another review notes that cutleaf teasel occupies wetter sites than Fuller's teasel .
Elevation: The elevational range for Fuller's teasel is available for several western states.Elevation range for Fuller's teasel in western United States State Elevation (feet) California < 5,600  Colorado 6,000-8,000  Nevada 4,000-6,500  New Mexico 4,000-7,000  Utah 4,690-8,730 
Soils: Reviews report that cutleaf teasel and Fuller's teasel grow best on similar soils. Hilty  reports that cutleaf teasel reaches its largest size on mesic, fertile, loamy soils and that size is reduced in "poor" soils. Uva and others  report that Fuller's teasel is frequent on damp, rich soils.
Although mesic conditions are typical, teasel sometimes occurs in dry areas [22,66,80]. The 2 species are only occasionally found together . Fuller's teasel may occupy sandy soils if moisture is not limited. Fuller's teasel also occurs in heavy clay soils with poor drainage and tolerates spring flooding . In west-central Montana, Fuller's teasel frequently occurs on disturbed soils with "appreciable water holding capacity" . Along Boulder Creek in Colorado, Fuller's teasel occurred with several other tall nonnative species on silty-sand deposits . In Kentucky and New Jersey, researchers noted that Fuller's teasel was especially common on limestone soils [36,78].
Salinity: Both Fuller's teasel and cutleaf teasel tolerate saline conditions [66,80]. However, many Fuller's teasel plants died before producing seed on an upper saltmarsh in Rittman, Ohio, where salinity levels reached 1.0% (Badger and Ungar personal observation 1988 cited in ).
Studies in Ontario, Canada, showed that site conditions may affect Fuller's teasel seed and seedling tolerances. When the germination and first 10 days of seedling growth were compared for Fuller's teasel seeds collected from roadside and old-field populations in Ontario, Canada, seeds from roadside plants were more salt tolerant than old-field seeds, and some roadside seedlings produced longer roots when grown in the presence of salt . Researchers suggested seed and seedling salinity tolerance was related to the salinity levels experienced by the parent plants. Seedlings that produced the longest roots in the presence of salt developed from seeds collected in the highest salinity environment. Seedlings grown from old-field seeds had decreased root development with salt exposure . Although emergence and first-year survival were similar for all seeds planted in old field and roadside habitats, regardless of source, no Fuller's teasel plants on the roadside reproduced within 4 years of seeding. Just 15% of plants were reproductive in the old field. A drought in June and July resulted in high seedling mortality in both habitats, but mortality was significantly greater on the roadside than in the old field (P<0.1) .
Impacts: Although few studies indicate the methods by which teasel impacts its nonnative habitats, several studies report that teasel may develop large monocultures , negatively impact riparian area integrity , and occupy habitats important to sensitive or threatened plant species . However in Michigan old fields, diversity and species richness were higher in early-seral old-fields with Fuller's teasel than in those without .
Several sources provide anecdotal information about teasel impacts. In northwestern North America, Taylor  describes Fuller's teasel as "truly noxious" in moist areas and capable of displacing native vegetation. Weber  notes that monotypic teasel stands can exclude other vegetation and may restrict wildlife movements. In a review, Glass  indicates that cutleaf teasel is "more aggressive" than Fuller's teasel and that cutleaf teasel has "severely threatened" the "natural quality" of several "high quality" prairies, savannas, seeps, and sedge meadows in northern and central Illinois. In these parts of Illinois, cutleaf teasel spread, since 1990 or earlier, was substantial (Solecki personal observation as cited in ). For more on the localized spread of teasel, see Local distribution changes.
Although several researchers and land managers consider teasel a potentially invasive nonnative species, Fuller's teasel was not a high-priority species in a list ranking those species thought to seriously reduce biodiversity. Fuller's teasel was listed number 80 in a prioritized list of 81 nonnative invasive species in natural Canadian habitats . However, several morphological and reproductive characteristics suggest teasel has the potential to be a problematic invasive species. A review reports that teasel's thick, well-developed taproot allows for substantial nutrient and water storage, which increases the potential for regrowth after damage and/or survival of inclement conditions. Barbs and spines defend teasel against herbivory and may focus grazing or browsing on unprotected associated vegetation. High levels of seed production, high seed germinability, and little dormancy in fresh seed allows for rapid establishment in open areas, and death of the parent provides habitat for future seedling recruitment .
Potential allelopathy: The leachate from Fuller's teasel seeds may affect germination of other Fuller's teasel seeds and may vary between Fuller's teasel populations. When seeds from old-field and roadside populations in Ontario, Canada, were germinated together, the initial root growth of old-field seeds was significantly shorter in the presence of roadside seeds than in the presence of other old-field seeds (P=0.02). Researchers found that roadside seeds leached significantly greater levels of sodium ions than old-field seeds (P<0.01) .
Riparian biotic integrity: In a survey of western riparian habitats, Fuller's teasel occurred more often in disturbed than undisturbed riparian areas (P<0.001). Riparian area biotic integrity, as measured by macroinvertebrate and vertebrate aquatic communities, was lower when Fuller's teasel was present than when it was absent (P<0.05) . Researchers did not distinguish the degree to which Fuller's teasel or past disturbance was impacting biotic integrity.
Other vegetation: In the early successional development of old fields in Michigan, the introduction of Fuller's teasel led to increased species richness overall, but the abundance of some native and nonnative forbs decreased with the introduction. In fields in Kalamazoo County, Michigan, species richness was significantly greater in fields with Fuller's teasel than in fields without (P<0.005). Typically species number increased in each of the 3 years after Fuller's teasel seeding. The introduction of Fuller's teasel increased the diversity in 87.5% of old-field plots. When Fuller's teasel reached flowering stage, community productivity was significantly greater in Fuller's teasel fields than in control fields (P=0.027) . Although diversity and species richness were higher in old fields with Fuller's teasel, desirability or nativity of the additional species was not assessed. During observations made up to 5 years after the introduction of Fuller's teasel in Michigan old fields, Werner  noted that abundance of the native hairy white oldfield aster (Symphyotrichum pilosum), native eastern daisy fleabane (Erigeron annuus), and nonnative Canada thistle (Cirsium arvense) decreased with increased Fuller's teasel abundance. However, another species, garden yellowrocket (Barbarea vulgaris), a nonnative winter annual, established in spaces created by dead Fuller's teasel plants and was restricted to Fuller's teasel fields .
In New Jersey and New Mexico, studies indicate that teasel populations may monopolize habitats utilized by threatened or endangered species. In a limestone fen in New Jersey's Warren County, dense teasel populations occupy habitats important to 2 state endangered species, American globeflower (Trollius laxus) and water speedwell (Veronica anagallis-catenata) . Over a 3- to 4-year period in central New Mexico, density of and area occupied by Fuller's teasel increased in habitat of the threatened Sacramento Mountain thistle. In about 20% of quadrats, Fuller's teasel and Sacramento Mountain thistle occurred within a 1 m² area. In several quadrats, seedling densities of Fuller's teasel exceeded 150 seedlings/m², whereas Sacramento Mountain thistle seedling densities rarely exceeded 20/m². A greenhouse study established that the 2 species had similar germination requirements, but that the germination of Sacramento Mountain thistle was significantly lower in dark than in light (P<0.05), while Fuller's teasel germinated equally well in dark and light conditions. When plant growth was monitored, Sacramento Mountain thistle was significantly smaller in pots with Fuller's teasel than in pots with only itself (P=0.02). Fuller's teasel growth was unaffected by the presence of Sacramento Mountain thistle . Grazing in Sacramento Mountain thistle habitats may foster establishment and persistence of Fuller's teasel .
Control: Several sources indicate that teasel control should focus on decreasing the density of established plants while preventing seed production and dispersal [22,80]. Early detection of teasel populations reduces the effort necessary to reduce established plant densities . Based on demography studies, researchers suggest that control of short-lived, rapidly growing nonnative plants should focus on limiting growth and reproduction rather than trying to impact survival of established plants .
Fire: For information on the use of prescribed fire to control this species, see Fire Management Considerations.
Prevention: Maintenance or restoration of wetlands, minimizing soil disturbances, and improving public education and behaviors could help to prevent teasel introductions and spread. When areas of Swavesey in Camridgeshire, England, were drained, Fuller's teasel established within 3 years in the lowland meadow . Teasel is often described in association with disturbed sites. Minimizing disturbances may decrease its establishment and spread . Changing human behaviors that encourage teasel seed dispersal could prevent teasel seed spread; however, from 1995 and 2000, Fuller's teasel seeds were available for sale in US plant nurseries .
Physical or mechanical: While some teasel plants may be killed by cutting or mowing, many sprout and some may still produce seed . Available literature (as of 2009) suggests that Fuller's teasel may be more susceptible to cutting than cutleaf teasel. Werner (Werner unpublished data cited in ) reported that repeated cutting eliminated Fuller's teasel stands, but no details were provided about the timing, frequency, or disposal methods used. Typically, researchers and land managers suggest that belowground cutting is most effective [29,90], but plants may still regenerate . Reduced seed production and plant death are most likely if plants are cut just before or as they flower . However, viable seeds may be produced on cut stems, making disposal of flowering stems in cut areas important to successful teasel control .
Although Fuller's teasel is not often the target of control efforts in the United Kingdom, Cheesman  conducted an experiment in field boundaries that provides potentially useful control information. Fuller's teasel stems were cut to height of 2 inches (5 cm) when they had flower buds, were beginning to flower, or producing mature seeds. Flower head production on the regrowth of stems cut at the bud stage was 78% to 94% lower than that of uncut Fuller's teasel stems. Twenty percent of plants regrew following cutting at the flowering stage but no cut stems produced seed. Stems cut when seed was maturing produced no new growth in the treatment or following year .
In the Loda Cemetery Prairie in Illinois, managers cut cutleaf teasel stems annually for 7 years and burned sites biennially. Cutting occurred when flower buds were present but before peak flowering. Cut stems were left on the treatment site. Cut-leaved teasel populations were not reduced by this management (Harty and White personal communication cited in ). Seeds from the cut stems germinated. After 1 and 7 months of room-temperature storage, 41% and 97%, respectively, of the seeds from cut stems germinated .
Mowing failed to control cutleaf teasel in the Mascoutin Recreation Area of DeWitt County, Illinois. When patches of similar size and plant density were mowed or undisturbed, the size of mowed patches increased by 33 m², while control patches increased by 4.2 m². Seed dispersal by mowing was considered the reason for increased patch size .
Biological: A review reported that moderate to heavy grazing can limit teasel establishment . It is unclear whether grazing and/or trampling restrict establishment. In 2006, insect, fungal, and viral biocontrols were being evaluated for potential biological control of teasel. Researchers predicted that organisms attacking the taproot or rosette may provide the most effective control .
Chemical: Early-spring or late-fall herbicide applications may allow managers to better target teasel plants, since much of the associated vegetation is dormant at this time . In Missouri, several herbicides used to treat cutleaf teasel provided some initial control. Residual herbicides did not prevent the next year's seedling emergence. In many cases, emergence on treated plots exceeded that on untreated plots. Openings created through herbicide-induced mortality may have provided suitable sites for germination . Survival of other plants on the site may have offered protection for seedlings and thus provided for seedling survival. See germination, seedling establishment, and the case study summary for additional information on these topics.Integrated management: Burning or mowing to expose rosettes before mechanical or chemical treatments may increase effectiveness .
Mice and voles may consume teasel seeds. During a study in southwestern Michigan old fields, the seed litter left at trays with Fuller's teasel seed suggested consumption by mice (Mittelbach personal observation as cited in ). On the Purdue University campus in west Lafayette, Indiana, American kestrels often hunted in grasslands where Fuller's teasel was abundant. American kestrels fed primarily on voles .
In the western United States, several game birds feed on Fuller's teasel seeds. On the Colville Confederated Tribal Reservation in Okanogan County, Washington, Fuller's teasel seeds were important in the winter diets of California quail and ring-necked pheasants. The frequency and volume of Fuller's teasel in California quail crops averaged 20% and 1.9%, respectively, in winter. The frequency and volume of Fuller's teasel in ring-necked pheasant crops averaged 16.7% and 5.8%, respectively, in the winter . In eastern Washington, Fuller's teasel seeds comprised over 5% of the winter diets of California quail . On the Palouse Prairie near Pullman, Washington, the winter stomach contents of northern bobwhites were 6% Fuller's teasel seed .
In other parts of North America, researchers have observed crossbills, goldfinches, and blackbirds feeding on teasel seed. In late December at Vineland Station, Ontario, Putnam  observed white-winged crossbills feeding on Fuller's teasel seeds. Others observed goldfinches (Ridley 1930 as cited in ) and blackbirds (Pohl and Sylwester 1963 as cited in ) feeding on teasel seeds.
Palatability and/or nutritional value: No information is available on this topic.
Teasel flowers bloom for only 1 day , and plants die after flowering. Teasel first develops a rosette and after 2 or more years, bolts and flowers. Rosette leaves generally die by the middle of the flowering season [18,31,32]. For more on teasel flowering, see Flower and seed production and Seedling establishment and plant growth.
Teasel plants flower from April to October throughout their nonnative ranges [30,33,48]. The earliest flowering dates, April to August, were reported for Fuller's teasel in California . Generally teasel flowering dates were later, July to October, in the midwestern and eastern United States and adjacent Canada [63,87,95]. In eastern North America, Fuller's teasel seeds mature and disperse from September to late November [69,95].
In the field, Fuller's teasel germinates in the spring or the fall. Werner  reported that most Fuller's teasel seed germinates from early April to early June in Canada, although early September germination also occurs. A small portion of Fuller's teasel seeds may remain dormant for a year and germinate the following spring . In a review of Fuller's teasel in the northeastern United States, researchers indicated that most Fuller's teasel seeds germinated in late summer or fall and overwintered as rosettes .
The teasel seed bank is short lived. While Fuller's teasel seeds stored indoors remained viable for 6 years or more [16,95], less than 1% of Fuller's teasel emerged after 5 years of storage in the soil . Seeds did not persist long in water. After 3 to 9 months in a canal in Prosser, Washington, the maximum germination of Fuller's teasel seeds was 2% . In a greenhouse study, Fuller's teasel seedlings emerged from soils taken from 3-to 5-inch (8-12 cm) depths in a northern Spain perennial grassland. Fuller's teasel did not occur in the aboveground vegetation .
Mature Fuller's teasel seed has little immediate dormancy (see Germination), suggesting short-term persistence in the soil. All Fuller's teasel seeds planted in old fields in Michigan germinated within 2 years . In an old field at the University of Toronto Joker's Hill Research Station, 40% to 60% of the Fuller's teasel seeds germinated after 4 months in pots buried in the soil, 30% to 50% germinated after 11 months of burial, and 20% to 50% germinated after 16 months of burial in the soil. After 16 months in the soil, germination was greatest from pots that were treated with fungicide before burial . After 5 years, just 0.9% of Fuller's teasel emerged from containers buried in southern Warwickshire, England .
Teasel seeds are not morphologically adapted for wind dispersal. In a field in Kalamazoo County, Michigan, 99.9% of Fuller's teasel seeds fell within 4.9 feet (1.5 m) of the parent plant . Water (Werner unpublished data as presented in ) and human activities [22,67] are the most likely methods of long-distance teasel seed dispersal.
Long-distance teasel seed dispersal by water is likely. Fuller's teasel seeds floated in water for 22 days without losing viability (Werner unpublished data as presented in ). Along busy roadways and mowed areas, teasel seed may dispersal 2 to 3 times farther than the maximum passive dispersal distance of 4.9 feet (1.5 m) reported by Werner . In a natural area near Clinton Lake, Illinois, just 1.3% of cutleaf teasel seeds made it to the farthest seed trap, which occurred 15 feet (4.5 m) from the source population. Along a nearby interstate, 3% of cutleaf teasel seeds dispersed 20 to 49 feet (6-15 m) from the source population . In the Mascoutin Recreation Area of DeWitt County, Illinois, the size of mowed cutleaf teasel patches increased by 360 feet² (33 m²) and unmowed patches increased by 45 feet² (4.2 m²) after 2 years of mowing. In mowed areas, 95% of cutleaf teasel seed dispersed within 20 feet (6 m) of the source population and more than 1% dispersed more than 30 feet (10 m) from the source .
Seed dispersal through the collection and use of dried teasel flower heads is probable. Several sources report that flower heads are collected and used in dried-flower decorations [22,32,92]. Reviews report that teasel often occurs in and around cemeteries and likely came from floral arrangements left at gravesides [22,40].
While teasel seed germination is most likely on open or exposed sites, seedling survival is often best on sites with moderate amounts of litter or beneath sparse vegetation, which decrease the potential of desiccation . However, seedling growth rates may be reduced by the presence of established vegetation. In the greenhouse, the relative growth rate of Fuller's teasel seedlings grown in litter or bare soil was about 0.08 mg/mg day, which was significantly greater than the rate in established vegetation and vegetation with litter, which was about 0.02 mg/mg day .
In the field, Fuller's teasel seedlings often occur in small canopy openings within established vegetation. Canopy openings may be created by mammals, frost heaving, or death of the parent plant . The probability of successful Fuller's teasel seedling establishment is several times greater in open sites left by the dead parent plant than in surrounding vegetation (Werner unpublished data cited in ). Teasel seedling densities may vary. In a mesic tallgrass prairie in east-central Illinois where cutleaf teasel was a dominant species, cutleaf teasel seedling densities ranged from 0 to 1,926 seedlings/3 m² .
Case study on Fuller's teasel development and survival: Established grass and heavy shrub cover may reduce Fuller's teasel germination and survival. Studies conducted in 2- to 3-year-old fields in southwestern Michigan compared these life stages in different vegetation types. In dense quackgrass and deep litter (over 0.4 inch (10 cm)), just 20% of planted Fuller's teasel seeds germinated, and all plants died before flowering. In grass-forb vegetation with minimal staghorn sumac (Rhus typhina) cover, Fuller's teasel germination was variable (25%-57%), rosettes grew rapidly, and the majority of plants flowered by year 2. In forb-dominated fields with heavy shrub shading, Fuller's teasel germination was high (58%), but plants did not mature beyond the seedling stage. By the 5th year, Fuller's teasel seed production in fields with reproducing plants was about 7 times (4,500 seeds/m²) more than the density of planted seeds (600 seeds/m²) .Fate of Fuller's teasel seeds, seedlings, and plants in various old-field habitats in southwestern Michigan (germination, mortality, and survival percentages are averages)  Grass cover Forb cover Little to no shrub shading Heavy shrub shading Very dense (95-100% quackgrass cover) Little to none
-low germination (20%)
-1st year seedling mortality 96%
-germination 25% to 57%, lowest in fields with more grass
-seedling survival high
-flowering in year 2 or 3
-low germination (24%)
-flowering by year 3
-moderate germination (43%)
-first year seedling survival high (15%)
-flowering by year 4
-high germination (58%)
-high first year seedling mortality (97%)
Teasel is common on disturbed sites and in early-seral habitats. While large, dense teasel populations are possible, without periodic disturbances they are likely to be replaced by slow-growing, late-seral species. Both teasel species grow best in full sun to partial shade and are common in canopy openings [22,40,95]. Because both species require 2 or more years to complete their life cycle, severe annual disturbances may not be tolerated.
The literature often describes teasel in disturbed habitats. Reviews report that teasel is common on open, disturbed sites [22,33,40,95], and some describe Fuller's teasel as "an aggressive competitor in disturbed areas" . While teasel establishment and spread are common on disturbed sites, teasel may also occur in established vegetation  and "high quality natural areas" .
Fuller's teasel appeared or increased in abundance with dredging, plowing, and grazing in its native and nonnative ranges. Fuller's teasel occurred 1 to 2 years after soils dredged from the Seneca Canal were deposited on an unnamed island in Cayuga Lake, New York . Five months after deep plowing (20 inches (50 cm)) occurred in a northern Spain perennial grassland, Fuller's teasel cover averaged 5.3%. Fuller's teasel did not occur in aboveground vegetation before plowing, but seed was present in the soil . In Washington, cattle grazing in black hawthorn (Crataegus douglasii) habitats often leads to an increase in Fuller's teasel abundance .
Studies of old-field succession show that although teasel may be abundant in recently disturbed, open sites, abundance typically decreases as time since disturbance increases. When the species composition of southwestern Ohio old fields was compared, Fuller's teasel was absent from 2-year-old fields, occurred in 10- and 50-year-old fields, but did not occur in fields older than 90 years old. Shrub cover in the 50-year-old field was about 30%, and fields abandoned 90 years or more were dominated by deciduous trees and shrubs .After conducting multiple field studies and making many observations in Michigan old fields, Werner  concluded that Fuller's teasel is not a "climax species" and in undisturbed fields is replaced by slow-growing perennials. Although death of the parent plant provides open sites for seedling establishment, the number and size of these openings decreases without periodic disturbances . Werner  observed near monocultures of Fuller's teasel locally in Michigan and noted that "when favorable conditions are present, (Fuller's teasel) will totally exclude other species". Even in monocultures, however, a lack of disturbances facilitates replacement by late-seral species. During old-field succession, late-seral species such as American elm (Ulmus americana) and summer grape (Vitis aestivalis) established in openings left by dying Fuller's teasel plants .
The genus name for teasels is Dipsacus L. (Dipsacaceae) . This review summarizes the information available as of 2009
on the following teasel species:
Dipsacus fullonum L., Fuller's teasel
Dipsacus laciniatus L., cutleaf teasel 
In this review, species are identified by their common names. Teasel is used for information that is common to both species.
Fuller's teasel and cutleaf teasel hybrids occur . Frequency of these hybrids was not reported. In a review, Solecki  reports that Fuller's teasel and cutleaf teasel are only occasionally found together.