Ceratocephala testiculata (bur buttercup)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Hosts/Species Affected
- Biology and Ecology
- Latitude/Altitude Ranges
- Air Temperature
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Impact Summary
- Economic Impact
- Environmental Impact
- Threatened Species
- Social Impact
- Risk and Impact Factors
- Similarities to Other Species/Conditions
- Prevention and Control
- Distribution Maps
Don't need the entire report?
Generate a print friendly version containing only the sections you need.Generate report
PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Ceratocephala testiculata (Crantz) Besser
Preferred Common Name
- bur buttercup
Other Scientific Names
- Ceratocephala orthoceras DC.
- Ceratocephala reflexa Steven
- Ranunculus orthoceras (DC.) Benth. & Hook.f. ex Schmalh.
- Ranunculus testiculatus Crantz
International Common Names
- English: burr buttercup; curveseed buttercup; curve-seed buttercup; curveseed butterwort; curve-seed butterwort; hornhead; hornseed buttercup; little bur; sage buttercup; testiculate buttercup
- French: renoncule mâle
- Russian: rogoglavnik pryamorogii; rogoglavnik yaichkovidnyi
- Chinese: jiao guo mao gen
Local Common Names
- Uzbekistan: kuitikan; uchma
Summary of InvasivenessTop of page
Ceratocephala testiculata is a dwarf, herbaceous annual plant, approximately 2-8 cm in height, native to southeastern Europe and Asia Minor. The species was introduced accidentally to the northern and western states of the USA and also to Canada and is considered to be an invasive weed of cereal crops, rangelands and pastures. In particular it invades disturbed land, and can form extensive, dense, monospecific mats. C. testiculata has spread rapidly throughout much of western North America, locally displacing native vegetation, and is spreading into the eastern half of the continent by attachment of its seed-bearing burs to human clothing and animal fur. This species is also potentially poisonous to livestock.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Dicotyledonae
- Order: Ranunculales
- Family: Ranunculaceae
- Genus: Ceratocephala
- Species: Ceratocephala testiculata
Notes on Taxonomy and NomenclatureTop of page
Ceratocephala is a genus of flowering plants belonging to the buttercup family, Ranunculaceae, and is closely related to the genus Ranunculus (Májeková et al., 2013). According to the Plant List (2013), Ceratocephala has four accepted species: C. caulifolia, C. falcata, C. pugens and C. testiculata, and C. testiculata itself has four major synonyms: C. orthoceras,C. reflexa, Ranunculus orthoceras and R. testiculatus.
C. testiculata is commonly known in English as bur (or burr) buttercup, but other names include curveseed butterwort, curve-seed buttercup and little bur. Named after the inflorescences which ripen into hard, spiny fruits or burs, the generic name Ceratocephala is derived from the Greek keras or keratos meaning a horn and kephale meaning the head. The specific epithet testiculata means testicle-shaped and likely refers to the two lateral bulges of the fruit achenes.
DescriptionTop of page
C. testiculata is an herbaceous winter annual plant approximately 2-8 cm in height which often occurs in dense mats covering large areas. Its leaves are attached at the base of the plant and are light green with short, white hairs. Flowers are very small, bright yellow and have 2-5 petals; they mature into hard, brown, spiny, bur-like seedheads (1.2 x 1 cm), each containing 5-80 seeds, which easily attach themselves to clothing and animal fur. They have a prickly appearance because of the sword-like beaks of the achenes. The root system is fibrous with a small taproot (Hilty, 2015; Utah State University Extension, 2016b).
The botanical description in the Flora of China states: outermost ca. 4 basal leaves sessile; leaf blade linear, 4-7 x 1-1.5 mm, glabrous or subglabrous; other basal leaves 4-11; petiole 0.3-2 cm, sparsely arachnoid; leaf blade broadly cuneate or flabellate-rhombic, 3-12 x 3-20 mm, sparsely arachnoid, base cuneate or broadly cuneate, 3-sect; segments unequally 1 or 2 x 2-sect, ultimate lobules linear. Scapes 1-5.8 cm, arachnoid. Flowers 6-9 mm in diameter. Receptacle glabrous. Sepals long elliptic, 2.5-4.5 mm, abaxially densely puberulent. Petals narrowly obovate or ligulate, 4-6 x 1.2-1.8 mm, apex rounded; scale ligulate, ca. 0.3 mm. Stamens 4-10, ca. 2.5 mm; anthers ca. 0.8 mm. Carpels 10-60, ca. 2 mm; ovary densely arachnoid, longer than style. Aggregate fruit subglobose to oblong, 0.3-2 x 0.5-1 cm; achenes 1.5-2 mm, arachnoid. Persistent style 1.5-5 x 0.7-0.9 mm, straight, sparsely arachnoid (Flora of China Editorial Committee, 2016).
DistributionTop of page
C. testiculata is native to southeastern Europe and southwestern Asia (Benson, 1948; Fischer et al., 2008), but it may exist in these areas as an adventive and have an origin in Central Asia. According to GBIF (2016), collections made in Algeria and Morocco represent native populations though the native status in North Africa is uncertain. It was introduced accidentally into the USA and Canada, and in the west and north-west it is now considered to be an invasive weed as it appears to be expanding its range rapidly in arid and semiarid areas (Flora of North America Editorial Committee, 2016). It is distributed widely in the temperate desert environment of the Intermountain Area of the western USA, extending from Utah, across northern Nevada to northeastern California (Munz, 1973). Isolated populations are known from northeastern Wyoming, northern Arizona, interior British Columbia (Canada), Nebraska, South Dakota and Kansas (Tuma and Weedon, 1989), as well as eastern Washington, eastern Oregon, Idaho and Colorado (Slichter, 2010). Although more common in the west, C. testiculata is also reported, but less frequently, in pockets in the eastern states, including central and northeastern Illinois (Hilty, 2015) and as far east as New York (Mitchell, 1995).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|China||Present||Present based on regional distribution.|
|Georgia (Republic of)||Present||Native||USDA-ARS, 2016|
|India||Present||Present based on regional distribution.|
|-Jammu and Kashmir||Present||Native||GBIF, 2016|
|Pakistan||Present||Native||USDA-ARS, 2016||in northern areas|
|Canada||Present||Present based on regional distribution.|
|-British Columbia||Localised||Introduced||Invasive||Tuma and Weedon, 1989; Canadensys, 2016|
|-Ontario||Localised||Introduced||Invasive||Oldham et al., 2006|
|USA||Present||Present based on regional distribution.|
|-Arizona||Localised||Introduced||Invasive||Tuma and Weedon, 1989||in north|
|-California||Widespread||Introduced||Invasive||Munz, 1973; Calflora, 2016||in east|
|-Illinois||Localised||Introduced||1991||Swink and Wilhelm, 1994; Hilty, 2015||isolated populations in central and northeastern areas|
|-Kansas||Localised||Introduced||1975||Invasive||Tuma and Weedon, 1989|
|-Missouri||Localised||Introduced||1987||Oldham et al., 2006|
|-Nebraska||Localised||Introduced||1970||Invasive||Tuma and Weedon, 1989|
|-Nevada||Widespread||Introduced||Invasive||Munz, 1973||in north|
|-New Mexico||Present||Introduced||Invasive||USDA-NRCS, 2016|
|-New York||Localised||Introduced||1990||Mitchell, 1995||in Orange County|
|-North Dakota||Present||Introduced||USDA-NRCS, 2016|
|-Oregon||Localised||Introduced||1938||Invasive||Slichter, 2010||in east|
|-South Dakota||Localised||Introduced||Invasive||Tuma and Weedon, 1989; Utah State University Extension, 2016|
|-Utah||Widespread||Introduced||1932||Invasive||Munz, 1973; USDA-NRCS, 2016|
|-Washington||Localised||Introduced||1940||Invasive||Slichter, 2010||in east|
|-Wyoming||Localised||Introduced||Invasive||Tuma and Weedon, 1989||in north-east|
|Czech Republic||Present||Native||USDA-ARS, 2016|
|Russian Federation||Present||Native||USDA-ARS, 2016|
|-Southern Russia||Present||Native||USDA-ARS, 2016|
|-Western Siberia||Present||Native||USDA-ARS, 2016|
|Slovakia||Present||Native||Májeková et al., 2013; USDA-ARS, 2016|
History of Introduction and SpreadTop of page
C. testiculata was first collected in the USA in Utah near Salt Lake City in 1932, with subsequent collections soon after in Oregon in 1938, Washington in 1940, Colorado in 1948, Nebraska in 1970 and Kansas in 1975 (Barkworth, 1982; Young et al., 1992). The first report of the species in eastern North America is based on a 1977 collection from South Bass Island in western Lake Erie in Ohio (Cusick, 1989). Subsequent reports came from Iowa in 1984 and Missouri in 1987 (Oldham et al., 2006). In New York State it was first collected in 1990 from a campsite in Orange County (Mitchell, 1995). The first Chicago area collection was made in 1991 (Swink and Wilhelm, 1994).
In Canada, bur buttercup has been known from southern British Columbia for some time (Scoggan, 1978), where it occurs infrequently in south-central and southeastern parts of the province in dry disturbed clearings and sagebrush slopes in the steppe zone (Douglas et al., 1999). A specimen was collected in Saskatchewan in 1987 (Cody, 1988) and in 2004 the species was found at two campsites in Ontario (Oldham et al., 2006).
An interesting aspect of the establishment of bur buttercup is that the spread of this species took place after many other highly competitive, alien annual species were already in place (Young et al., 1992), as annual communities are often considered closed to seedling establishment by other species (Mack, 1981).
In Slovakia, the species had been classified as extinct but after more than 40 years it was rediscovered by a railway station in 2013 (Májeková et al., 2013).
IntroductionsTop of page
Risk of IntroductionTop of page
Several authors have noted the affinity of this species for camping grounds, particularly in eastern North America; for example, the first reports from Iowa, Missouri, New York, Ohio and the Chicago area were all from campsites. It seems likely that this species is dispersed by camping vehicles and associated equipment. The bur-like fruiting heads of the bur buttercup may readily attach to blankets and tents, and are thus carried to campsites that appear to provide ideal disturbed conditions for establishment (Oldham et al., 2006). With the continued popularity of camping as a leisure activity and the greater mobility of campers, it seems likely that C. testiculata will be introduced to other areas of North America by this means.
HabitatTop of page
In its native range, C. testiculata grows along river banks, on dry slopes and in deserts at elevations of 600-1600 m above sea level (Flora of China Editorial Committee, 2016). It prefers open ground with little competition from other kinds of plants, but is very adaptable to environmental conditions and will tolerate both wet and dry soils.
It is a weed of cereal and small-grain crops. In western North America, where it is fairly widespread as a weed, it can be found growing in lawns, gardens, roadsides, driveways, wasteland, pastures, cropland and rangeland; when present in large numbers, it is usually an indication of excessive disturbance to the land (Hilty, 2015; Utah State University Extension, 2016a). In the eastern states of the USA, where populations are relatively localized, typical habitats consist of campsites, picnic areas and car parking lots in parks, particularly in areas where the ground is barren from too much trampling. Bur buttercup can also be found on overgrazed lands and areas heavily impacted by off-road driving (Slichter, 2010; Hilty, 2015).
Habitat ListTop of page
|Terrestrial – Managed||Cultivated / agricultural land||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Managed grasslands (grazing systems)||Present, no further details|
|Disturbed areas||Principal habitat||Harmful (pest or invasive)|
|Disturbed areas||Principal habitat||Natural|
|Rail / roadsides||Principal habitat||Harmful (pest or invasive)|
|Rail / roadsides||Principal habitat||Natural|
|Urban / peri-urban areas||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Urban / peri-urban areas||Secondary/tolerated habitat||Natural|
|Terrestrial ‑ Natural / Semi-natural||Natural grasslands||Principal habitat||Harmful (pest or invasive)|
|Natural grasslands||Principal habitat||Natural|
|Scrub / shrublands||Principal habitat||Harmful (pest or invasive)|
|Scrub / shrublands||Principal habitat||Natural|
|Arid regions||Principal habitat||Natural|
Hosts/Species AffectedTop of page
It is a weed of cereal and small-grain crops.
Biology and EcologyTop of page
The chromosome number of C. testiculata is 2n = 14, although 2n = 28 has been reported for material from Iran (Kiehn et al., 1991).
C. testiculata reproduces by seed. Germination experiments by Young et al. (1992) found that germination in the laboratory was generally highest at cooler temperatures, with anything above 30°C greatly suppressing or inhibiting germination. Liu et al. (2015) have also examined seed dispersal and germination for this species and 69 others from the cold Gurbantunggut Desert in northwest China.
Physiology and Phenology
Most growth and development occurs during cool weather. Bur buttercup seeds germinate in early spring, when temperatures reach about 5°C, and seedlings emerge soon after. The plant flowers within 3 weeks of emergence, with flowering in April-May and fruiting in May. The flowerheads develop into spiny burs, and by early summer the entire plant dries out and turns brown and brittle (Flora of China Editorial Committee, 2016; Utah State University Extension, 2016a).
C. testiculata flowers are probably cross-pollinated by small bees and flies (Hilty, 2015).
Bur buttercup, like other members of the Ranunculaceae, produces ranunculin, a toxin which makes the plant poisonous to grazing animals. Sheep are particularly susceptible and 0.5 kg of plant material is reported to be enough to kill a 45 kg animal (Olsen et al., 1983).
Population Size and Structure
Without competition, C. testiculata plants can form dense mats covering large areas of ground (Utah State University Extension, 2016b).
In pastures, C. testiculata is associated with Kentucky bluegrass (Poa pratensis), cheatgrass (Bromus tectorum) and annual crested wheatgrass (Eremopyrum triticeum) (Utah State University Extension, 2016b).
Bur buttercup often forms associations with soil fungi that enable it to take up nutrients very efficiently, allowing it to grow in poor quality soils (Utah State University Extension, 2016a).
The seedheads of C. testiculata are a source of food to gamebirds such as the ring-necked pheasant and wild turkeys in Canada (Hilty, 2015).
C. testiculata is very adaptable and can tolerate a range of conditions, from moist to very dry. Drought tolerance is good, but temperatures above 30°C greatly suppress or inhibit germination (Young et al. 1992). The preference is full or partial sun, mesic to dry conditions, and a barren soil that is sandy, gravelly or compacted from trampling. This dwarf plant prefers open ground with little competition from other plants. The seeds require exposure to cold weather in order to germinate (Young et al, 1992; Hilty, 2015).
ClimateTop of page
|BS - Steppe climate||Preferred||> 430mm and < 860mm annual precipitation|
|BW - Desert climate||Preferred||< 430mm annual precipitation|
|Cf - Warm temperate climate, wet all year||Tolerated||Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year|
|Cs - Warm temperate climate with dry summer||Tolerated||Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers|
|Ds - Continental climate with dry summer||Preferred||Continental climate with dry summer (Warm average temp. > 10°C, coldest month < 0°C, dry summers)|
Latitude/Altitude RangesTop of page
|Latitude North (°N)||Latitude South (°S)||Altitude Lower (m)||Altitude Upper (m)|
Air TemperatureTop of page
|Parameter||Lower limit||Upper limit|
|Mean maximum temperature of hottest month (ºC)||30|
Notes on Natural EnemiesTop of page
Aphids, sawfly larvae and other insects are known to feed on bur buttercups, but these are species mostly confined to wetlands and woodlands (Hilty, 2015).
Means of Movement and DispersalTop of page
The lightweight burs of C. testiculata, each containing 5-80 hard, dry seeds, can be easily picked up and carried by water, to be widely distributed (Utah State University Extension, 2016a).
Vector Transmission (Biotic)
C. testiculata is dispersed by seed. Humans and animals are thought to be responsible for the movement of seed to new sites. The seedheads cling to the fur of animals and the feathers of birds and can be dispersed long distances before falling off (Hilty, 2015).
The burs of C. testiculata attach themselves to items such as clothing, blankets, tents and shoes and are distributed to new areas by humans, often great distances, which is one of the reasons why C. testiculata is often found at campsites and picnic areas in parks with natural areas in North America (Hilty, 2015).
Impact SummaryTop of page
|Human health||Positive and negative|
Economic ImpactTop of page
The bur buttercup plant contains ranunculin, which changes into the highly toxic compound protoanemonin when the plant is crushed. Sheep have been poisoned and have died in the western USA after ingesting aboveground plant material of bur buttercup. The plant is consequently considered highly toxic. Signs of poisoning include anorexia, diarrhoea, dyspnoea, recumbency, weakness and ultimately death (Utah State University Extension, 2016b). Around 0.5 kg of plant material is reported to be enough to kill a 45 kg animal (Nachman and Olsen, 1983; Olsen et al., 1983; Gunn et al., 2007), so presumably there are cost implications for farmers from such poisonings.
Environmental ImpactTop of page
Impact on Biodiversity
Without competition, C. testiculata plants can form dense mats covering large areas of ground (Utah State University Extension, 2016b).
C. testiculata is one of the alien weed species which has been highlighted as invading the habitat of Castilleja cinerea (ash-gray paintbrush), a federally listed threatened native plant species in the USA, and is included in a 5-year review for ongoing monitoring of the species in the pebble plain complexes of the San Bernardino Mountains in California (US Fish and Wildlife Service, 2013).
Although Buchanan et al. (1978) demonstrated strong allelopathic effects of bur buttercup tissue on the growth of five grass species in vitro, these effects were not significant on the germination and growth of seven grasses and two herbs when tested in soil.
The seedheads of C. testiculata are a source of food to gamebirds such as the ring-necked pheasant and wild turkeys in Canada (Hilty, 2015).
Threatened SpeciesTop of page
Social ImpactTop of page
The plant’s sap can cause irritation to human skin. The burs of C. testiculata often attach to socks, blankets and the canvas of tents and are a general nuisance at campsites and picnic areas. The stiff, prickly burs can be painful when stepped on, but are no longer toxic at this stage (Utah State University Extension, 2016a).
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Has a broad native range
- Highly adaptable to different environments
- Pioneering in disturbed areas
- Tolerant of shade
- Benefits from human association (i.e. it is a human commensal)
- Fast growing
- Ecosystem change/ habitat alteration
- Monoculture formation
- Negatively impacts animal health
- Reduced amenity values
- Reduced native biodiversity
- Threat to/ loss of endangered species
- Threat to/ loss of native species
- Causes allergic responses
- Competition - monopolizing resources
- Produces spines, thorns or burrs
- Highly likely to be transported internationally accidentally
UsesTop of page
C. testiculata is used in traditional medicine in Central Asia to treat wounds, injuries, eczema and other skin diseases. An ointment is made of the dried herb for this purpose. Oil extracts of the fresh herb have been shown to accelerate the reduction of inflammatory oedema and stimulate a steady increase in tissue granulation and wound epithelialization (Khalmatov, 1964; Zaurov et al., 2013).
Similarities to Other Species/ConditionsTop of page
C. testiculata is very similar to Ranunculus species, but is easily distinguished from them due to its dwarf size, distinctive prickly seedheads and deeply divided leaves. It is also unusual in often having flowers with as few as two petals, instead of the usual five (Hilty, 2015).
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
Cultural Control and Sanitary Measures
It is best to control C. testiculata before flowers and seeds are produced. It grows poorly when competing with grasses or other aggressive plants, and therefore maintaining a vigorous, desirable plant population will discourage its establishment (Utah State University Extension, 2016a).
Early hoeing, digging, hand pulling and tilling before flowering are very effective at controlling bur buttercup (Lowry et al., 2015; Utah State University Extension, 2016a). Good control (80-95%) can also be achieved with early mowing or cutting (DiTomaso et al., 2013). Burning is also a good form of control, if the area permits (Utah State University Extension, 2016b).
A number of chemical options are available that provide excellent control (>95%) and include the herbicides chlorsulfuron, aminocyclopyrachlor + chlorsulfuron, dicamba, glyphosate, metsulfuron, picloram, sulfometuron and triclopyr (DiTomaso et al., 2013). Utah State University Extension (2016b) also recommends 2,4-D, glufosinate-ammonium and dicamba + 2,4-D.
ReferencesTop of page
Barkworth ME, 1982. Bur buttercup: a weedy immigrant. Utah Science, 43(1):7-9.
Benson LD, 1948. A treatise on the North American Ranunculi. American Midland Naturalist, 40(1):1-261.
Buchanan BA; Harper KT; Frischknecht NC, 1978. Allelopathic effects of bur buttercup tissue on germination and growth of various grasses and forbs in vitro and in soil. Great Basin Naturalist, 38(1):90-96.
Calflora, 2016. Information on California plants for education, research, and conservation. Berkeley, California, USA: Calflora Database. http://www.calflora.org
Canadensys, 2016. Canada-wide biodiversity information network. Universite de Montreal Biodiversity Centre. Montreal, QC, Canada: Universite de Montreal Biodiversity Centre. http://data.canadensys.net/explorer/en/search
Cody WJ, 1988. Hornseed buttercup, Ceratocephalus testiculatus: a new record for the adventive flora of Saskatchewan. Canadian Field-Naturalist, 102(1):71-73.
Cusick AW, 1989. Bur buttercup (Ceratocephalus testiculatus: Ranunculaceae): a poisonous plant newly established in Ohio. Michigan Botanist, 28(1):33-35.
DiTomaso JM; Kyser GB; Oneto SR; Wilson RG; Orloff SB; Anderson LW; Wright SD; Roncoroni JA; Miller TL; Prather TS, 2013. Weed control in natural areas in the western United States. Davis, California, USA: Weed Research and Information Center, University of California, 544 pp.
Douglas GW; Meidinger D; Pojar J, 1999. Illustrated flora of British Columbia, Volume 4: Dicotyledons (Orobanchaceae through Rubiaceae). Victoria, BC, Canada: BC Ministry of the Environment, Lands and Parks, and BC Ministry of Forests, 427 pp.
Fischer MA; Oswald K; Adler W, 2008. A field flora for Austria, Liechtenstein and South Tyrol. 3rd Edition (Exkursionsflora für Österreich, Liechtenstein und Südtirol. 3. Auflage). Linz, Austria: Biologiezentrum der Oberosterreichischen Landesmuseen, 1391 pp.
Flora of China Editorial Committee, 2016. Flora of China. St. Louis, Missouri and Cambridge, Massachusetts, USA: Missouri Botanical Garden and Harvard University Herbaria. http://www.efloras.org/flora_page.aspx?flora_id=2
Flora of North America Editorial Committee, 2016. Flora of North America North of Mexico. St. Louis, Missouri and Cambridge, Massachusetts, USA: Missouri Botanical Garden and Harvard University Herbaria. http://www.efloras.org/flora_page.aspx?flora_id=1
GBIF, 2016. Global Biodiversity Information Facility. http://www.gbif.org/species
Gunn D; Panter KE; Gardner DR; Pfister JA, 2007. Poisonous range plants on the Fort Hall Reservation in Southeastern Idaho. In: Poisonous plants: global research and solutions [ed. by Panter, K. E.\Wierenga, T. L.\Pfister, J. A.]. Wallingford, UK: CABI, 423-431.
Hilty J, 2015. Illinois wildflowers. Illinois, USA. http://www.illinoiswildflowers.info/index.htm
Khalmatov KhKh, 1964. Wild-growing medicinal plants of Uzbekistan (Dikorastushchie lekarstvennye rasteniya Uzbekistana). Tashkent, Uzbekistan: Meditsina, 278 pp.
Kiehn M; Vitek E; Hellmayr E; Walter J; Tschenett J; Justin C; Mann M, 1991. Contributions to the flora of Austria - chromosome counts. (Beitrage zur Flora von Osterreich - Chromosomenzahlungen.) Verhandlungen der Zoologisch-Botanischen Gesellschaft in Osterreich, 128:19-39.
Liu HuiLiang; Zhang DaoYuan; Yang XueJun; Huang ZhenYing; Duan ShiMin; Wang XiYong, 2014. Seed dispersal and germination traits of 70 plant species inhabiting the Gurbantunggut Desert in northwest China. The Scientific World Journal, 2014:Article ID 346405. http://www.hindawi.com/journals/tswj/2014/346405/
Lowry BJ; Whitesides RE; Dewey SA; Ransom CV; Banner RE, 2015. Common weeds of the yard and garden: a guidebook. Logan, Utah, USA: Utah State University Extension, 120 pp. https://extension.usu.edu/weedguides/files/uploads/Ranunculaceae.pdf
Mack RM, 1981. Invasion of Bromus tectorum L. into western North America: an ecological chronicle. Agro-Ecosystems, 7(2):145-165.
Májeková J; Zaliberová M; Jehlík V, 2013. Extinct species Ceratocephala testiculata (Crantz) Besser rediscovered in Slovakia after 44 years. Thaiszia - Journal of Botany, 23(2):141-145. http://www.upjs.sk/public/media/9724/141-145-majekova-et-al-upr.pdf
Mitchell RS, 1995. More new exotic species and hybrids in New York. NYFA Newsletter, 6(3):3-4.
Munz PA, 1973. A California flora and supplement. Berkeley, California, USA: University of California Press, 1905 pp.
Scoggan HJ, 1978. The flora of Canada, Part 3 - Dicotyledoneae (Saururaceae to Violaceae). Ottawa, Quebec, Canada: National Museum of Natural Sciences, National Museums of Canada, 568 pp.
Slichter P, 2010. Curveseed butterwort, hornseed buttercup: Ranunculus testiculatus. The buttercups of the Columbia River Gorge. http://science.halleyhosting.com/nature/gorge/5petal/butter/ran/testiculatus.htm
Swink F; Wilhelm G, 1994. Plants of the Chicago region. 4th edition. Indianapolis, USA: Indiana Academy of Science, 921 pp.
The Plant List, 2013. The Plant List: a working list of all plant species. Version 1.1. London, UK: Royal Botanic Gardens, Kew. http://www.theplantlist.org
Tuma WC; Weedon RR, 1989. Bur buttercup: migrant and killer. Nebraska Section Society for Range Management Newsletter, 38:2-4.
US Fish and Wildlife Service, 2013. Castilleja cinerea (ash-gray paintbrush). 5-Year review: summary and evaluation. Carlsbad, CA, USA: US Fish and Wildlife Service, 45 pp. http://ecos.fws.gov/docs/five_year_review/doc4138.pdf
USDA-ARS, 2016. Germplasm Resources Information Network (GRIN). National Plant Germplasm System. Online Database. Beltsville, Maryland, USA: National Germplasm Resources Laboratory. https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch.aspx
USDA-NRCS, 2016. The PLANTS Database. Baton Rouge, USA: National Plant Data Center. http://plants.usda.gov/
Utah State University Extension, 2016. Bur buttercup. Weed Guides. Logan, UT, USA: Utah State University. https://extension.usu.edu/weedguides/files/uploads/Ranunculaceae.pdf
Utah State University Extension, 2016. Range plants of Utah: bur buttercup. Logan, UT, USA: Utah State University. http://extension.usu.edu/rangeplants/htm/bur-buttercup
Zaurov DE; Belolipov IV; Kurmukov AG; Sodombekov IS; Akimaliev AA; Eisenman S, 2013. The medicinal plants of Uzbekistan and Kyrgyzstan. In: Medicinal plants of Central Asia: Uzbekistan and Kyrgyzstan [ed. by Eisenman, S. W. \Zaurov, D. E. \Struwe, L.]. New York, USA: Springer, 15-273.
ContributorsTop of page
14/03/2016 Original text by:
Sarah Thomas and Andrew Praciak, CABI, UK
Distribution MapsTop of page
Unsupported Web Browser:
One or more of the features that are needed to show you the maps functionality are not available in the web browser that you are using.
Please consider upgrading your browser to the latest version or installing a new browser.
More information about modern web browsers can be found at http://browsehappy.com/