Invasive Species Compendium

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Hypochaeris radicata
(cat's ear)

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Datasheet

Hypochaeris radicata (cat's ear)

Summary

  • Last modified
  • 16 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Pest
  • Host Plant
  • Preferred Scientific Name
  • Hypochaeris radicata
  • Preferred Common Name
  • cat's ear
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Dicotyledonae
  • Summary of Invasiveness
  • H. radicata is a herbaceous perennial originally native to Morocco. It is a very successful colonizing species that is now present on all continents except Antarctica (...

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Pictures

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PictureTitleCaptionCopyright
Hypochaeris radicata (common cat's ear); single composite flower head.
TitleFlower head
CaptionHypochaeris radicata (common cat's ear); single composite flower head.
Copyright©Trevor James/Hamilton, New Zealand-2014
Hypochaeris radicata (common cat's ear); single composite flower head.
Flower headHypochaeris radicata (common cat's ear); single composite flower head.©Trevor James/Hamilton, New Zealand-2014
Hypochaeris radicata (common cat's ear); flowering plant.
TitleFlowering plant
CaptionHypochaeris radicata (common cat's ear); flowering plant.
Copyright©Trevor James/Hamilton, New Zealand-2014
Hypochaeris radicata (common cat's ear); flowering plant.
Flowering plantHypochaeris radicata (common cat's ear); flowering plant.©Trevor James/Hamilton, New Zealand-2014
Hypochaeris radicata (common cat's ear); vegetative rosette.
TitleVegetative rosette
CaptionHypochaeris radicata (common cat's ear); vegetative rosette.
Copyright©Trevor James/Hamilton, New Zealand-2014
Hypochaeris radicata (common cat's ear); vegetative rosette.
Vegetative rosetteHypochaeris radicata (common cat's ear); vegetative rosette.©Trevor James/Hamilton, New Zealand-2014

Identity

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Preferred Scientific Name

  • Hypochaeris radicata L.

Preferred Common Name

  • cat's ear

Other Scientific Names

  • Hypochoeris radicata L.

International Common Names

  • English: Catsear dandelion; common catsear; Flatweed; hairy cat's ear; spotted catsear
  • Spanish: Hierba de halcon
  • French: porcelle; Porcelle enracinee
  • Portuguese: almeirao-do-campo; leituga

Local Common Names

  • : cat's ears; coast dandelion; common cat's ear; false dandelion; flatweed; frogbit; Gosmore; hairy catsear; long-rooted cat's ear; pee-the-bed; rooted cat's ear; rooted cat's-ear; wild dandelion
  • : chicorée; chicorée-pays; herbe à l’épervier; porcelle enracinée
  • Brazil: almeirão-do-campo (Portuguese); almeirão-roseta (Portuguese)
  • Germany: Gemeines Ferkelkraut; Gewönliches Ferkelkraut
  • Italy: Porcellina giuncolina; Scorzonera selvatica
  • Japan: Butana; Tanpopomodoki
  • Netherlands: gewoon Biggekruid
  • Sweden: rotfibbla

EPPO code

  • HRYRA (Hypochoeris radicata)

Summary of Invasiveness

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H. radicata is a herbaceous perennial originally native to Morocco. It is a very successful colonizing species that is now present on all continents except Antarctica (Ortiz et al., 2008). In New Zealand, Healy (1992) described the distribution of the introduced H. radicata as ‘one of, if not the most widely distributed introduced weeds on a geographical and altitudinal basis.’ It is considered one of the most invasive alien plants on the island of La Reunion (ISSG, 2013). H. radicata readily invades freshly disturbed environments, such as Mount St. Helens following its 1980 eruption (Schoenfelder et al., 2010), and can crowd out more palatable and productive forage species when it invades overgrazed pasture and rangeland (DiTomaso et al., 2013). PIER (2014) indicated it is invasive in a wide range of territories and islands around the Pacific.

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Dicotyledonae
  •                     Order: Asterales
  •                         Family: Asteraceae
  •                             Genus: Hypochaeris
  •                                 Species: Hypochaeris radicata

Notes on Taxonomy and Nomenclature

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Linnaeus was not consistent in his spelling of this species’ generic name, initially naming it Hypochaeris but later Hypochoeris (Aarssen, 1981). Both names have since been used by different authorities. ITIS (2013) prefered the form Hypochaeris radicata. Mabberley (1997) included 60 species in the genus Hypochaeris: nine from Europe and the others from Asia, North Africa and especially South America

Description

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Modified from Aarssen (1981):

Herbaceous perennial growing from hard, thickened, overwintering base (caudex); fibrous-rooted, but often with several enlarged roots, appearing tap-rooted; leaves in a basal rosette, hairv (hispid), oblanceolate, toothed or pinnatifid, 3-25 cm long and 0.5-7 cm wide; stems (stalks) 15-60 cm tall , branched above, or in small plants simple, sparsely and minutely bracteate, or naked, often spreading-hispid below, possessing a ‘milky’ juice; leafless, with small scale-like bracts only; flower heads (capitula) yellow, 20-30 (-40) mm wide, usually several, terminating the branches and rather showy; florets ligulate, monoclinous and bisexual, the ligules surpassing the involucre and about four times as long as wide; involucre l0-15 mm high at anthesis, up to about 25 mm in fruit, its bracts imbricate, glabrous or hispid; fruit an achene, orange or brown, body of the achene mostly 4-7 mm long, from a little longer to more often much shorter than the slender beak, the prominent nerves and the lower part of the beak muricate; pappus plumose with two rows of hairs, shorter outer hairs commonly merely barbellate.

Plant Type

Top of page Herbaceous
Perennial
Seed propagated

Distribution

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H. radicata is a very successful colonizing species that is now present on all continents except Antarctica (Ortiz et al., 2008). It tends to be distributed in cooler, temperate parts of the world (Turkington and Aarssen, 1983). Its northern limit may be controlled more by winter cold than by lack of summer warmth.

Both Turkington and Aarssen (1983) and Ortiz et al. (2008) have questioned whether the species is truly native to the UK and Europe. Ortiz et al. (2008) proposed that the native area of distribution should be North Africa, the Iberian Peninsula and the central (and possibly eastern) Mediterranean.

Although widespread in the USA, H. radicata seems to have stabilized there and, according to DiTomaso et al. (2013), is not likely to expand beyond its present habitats. 

Distribution Table

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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/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

AzerbaijanPresentNativeUSDA-NRCS, 2013
ChinaPresentIntroducedUSDA-NRCS, 2013Yunnan
-YunnanPresentIntroducedUSDA-NRCS, 2013
Georgia (Republic of)PresentNativeUSDA-NRCS, 2013
IndiaPresentIntroducedUSDA-NRCS, 2013
JapanPresentIntroduced Invasive USDA-NRCS, 2013; PIER, 2014
Korea, Republic ofUnconfirmed recordCAB Abstracts
TaiwanPresentIntroducedUSDA-NRCS, 2013; eFloras, 2014
TurkeyPresentNativeUSDA-NRCS, 2013

Africa

AlgeriaPresentNativeUSDA-NRCS, 2013; GBIF, 2014
EthiopiaPresentIntroducedGBIF, 2014
LesothoPresentIntroducedUSDA-NRCS, 2013
LibyaPresentNativeUSDA-NRCS, 2013
MadagascarPresentIntroducedUSDA-NRCS, 2013
MoroccoPresentNativeUSDA-NRCS, 2013
MozambiquePresentIntroducedUSDA-NRCS, 2013
RéunionPresentIntroducedUSDA-NRCS, 2013
Saint HelenaPresentIntroducedGBIF, 2014
South AfricaPresentIntroducedUSDA-NRCS, 2013
Spain
-Canary IslandsPresentNativeUSDA-NRCS, 2013
SwazilandPresentIntroducedUSDA-NRCS, 2013
TunisiaPresentNativeUSDA-NRCS, 2013
ZimbabwePresentIntroducedUSDA-NRCS, 2013

North America

CanadaPresentPresent based on regional distribution.
-British ColumbiaPresentIntroducedUSDA-ARS, 2013
-New BrunswickPresentIntroducedUSDA-ARS, 2013
-Newfoundland and LabradorPresentIntroducedUSDA-ARS, 2013
-Nova ScotiaPresentIntroducedUSDA-ARS, 2013
-OntarioPresentIntroducedUSDA-ARS, 2013
-QuebecPresentIntroducedUSDA-ARS, 2013
-SaskatchewanPresentIntroducedUSDA-ARS, 2013
MexicoPresentIntroducedGBIF, 2014
Saint Pierre and MiquelonPresentIntroducedUSDA-ARS, 2013
USAPresentPresent based on regional distribution.
-AlabamaPresentIntroducedUSDA-ARS, 2013
-AlaskaPresentIntroducedUSDA-ARS, 2013
-ArkansasPresentIntroducedUSDA-ARS, 2013
-CaliforniaPresentIntroducedUSDA-ARS, 2013
-ColoradoPresentIntroducedUSDA-ARS, 2013
-ConnecticutPresentIntroducedUSDA-ARS, 2013
-DelawarePresentIntroducedUSDA-ARS, 2013
-District of ColumbiaPresentIntroducedUSDA-ARS, 2013
-FloridaPresentIntroducedUSDA-ARS, 2013
-GeorgiaPresentIntroducedUSDA-ARS, 2013
-HawaiiPresentIntroduced Invasive USDA-ARS, 2013; PIER, 2014All main islands
-IdahoPresentIntroducedUSDA-ARS, 2013
-IllinoisPresentIntroducedUSDA-ARS, 2013
-IndianaPresentIntroducedUSDA-ARS, 2013
-KentuckyPresentIntroducedUSDA-ARS, 2013
-LouisianaPresentIntroducedUSDA-ARS, 2013
-MainePresentIntroducedUSDA-ARS, 2013
-MarylandPresentIntroducedUSDA-ARS, 2013
-MassachusettsPresentIntroducedUSDA-ARS, 2013
-MichiganPresentIntroducedUSDA-ARS, 2013
-MississippiPresentIntroducedUSDA-ARS, 2013
-MissouriPresentIntroducedUSDA-ARS, 2013
-MontanaPresentIntroducedUSDA-ARS, 2013
-NevadaPresentIntroducedUSDA-ARS, 2013
-New HampshirePresentIntroducedUSDA-ARS, 2013
-New JerseyPresentIntroducedUSDA-ARS, 2013
-New MexicoPresentIntroducedUSDA-ARS, 2013
-New YorkPresentIntroducedUSDA-ARS, 2013
-North CarolinaPresentIntroducedUSDA-ARS, 2013
-OhioPresentIntroducedUSDA-ARS, 2013
-OregonPresentIntroducedUSDA-ARS, 2013
-PennsylvaniaPresentIntroducedUSDA-ARS, 2013
-Rhode IslandPresentIntroducedUSDA-ARS, 2013
-South CarolinaPresentIntroducedUSDA-ARS, 2013
-TennesseePresentIntroducedUSDA-ARS, 2013
-TexasPresentIntroducedUSDA-ARS, 2013
-UtahPresentIntroducedUSDA-ARS, 2013
-VermontPresentIntroducedUSDA-ARS, 2013
-VirginiaPresentIntroducedUSDA-ARS, 2013
-WashingtonPresentIntroducedUSDA-ARS, 2013
-West VirginiaPresentIntroducedUSDA-ARS, 2013
-WisconsinPresentIntroducedUSDA-ARS, 2013

Central America and Caribbean

BarbadosPresentIntroducedGBIF, 2014
Costa RicaPresentIntroducedUSDA-NRCS, 2013; PIER, 2014
GuatemalaPresentIntroducedUSDA-NRCS, 2013; PIER, 2014
JamaicaPresentIntroducedUSDA-NRCS, 2013

South America

ArgentinaPresentIntroducedUSDA-NRCS, 2013
BoliviaPresentIntroducedGBIF, 2014
BrazilPresentPresent based on regional distribution.
-ParanaPresentIntroducedUSDA-NRCS, 2013
-Rio Grande do SulPresentIntroducedUSDA-NRCS, 2013
-Santa CatarinaPresentIntroducedUSDA-NRCS, 2013
-Sao PauloPresentIntroducedUSDA-NRCS, 2013
ChilePresentIntroduced Invasive USDA-NRCS, 2013; PIER, 2014Mainland and Juan Fernandez and Easter islands
ColombiaPresentIntroducedPIER, 2013
EcuadorPresentIntroducedUSDA-ARS, 2013; PIER, 2014
Falkland IslandsPresentIntroducedGBIF, 2014
UruguayPresentIntroducedUSDA-NRCS, 2013

Europe

AlbaniaPresentNativeUSDA-NRCS, 2013
AndorraPresentIntroducedGBIF, 2014
AustriaPresentNativeUSDA-NRCS, 2013
BelarusPresentNativeUSDA-NRCS, 2013
BelgiumPresentNativeUSDA-NRCS, 2013
Bosnia-HercegovinaPresentNativeUSDA-NRCS, 2013
BulgariaPresentNativeUSDA-NRCS, 2013
CroatiaPresentNativeUSDA-NRCS, 2013
Czech RepublicPresentNativeUSDA-NRCS, 2013
DenmarkPresentNativeUSDA-NRCS, 2013
EstoniaPresentNativeUSDA-NRCS, 2013
FinlandPresentNativeGBIF, 2014
FrancePresentNativeUSDA-NRCS, 2013
GermanyPresentNativeUSDA-NRCS, 2013
GreecePresentNativeUSDA-NRCS, 2013
HungaryPresentNativeUSDA-NRCS, 2013
IrelandPresentNativeUSDA-NRCS, 2013
ItalyPresentNativeUSDA-NRCS, 2013
LatviaPresentNativeUSDA-NRCS, 2013
LiechtensteinPresentNativeGBIF, 2014
LithuaniaPresentNativeUSDA-NRCS, 2013
MoldovaPresentNativeUSDA-NRCS, 2013
MontenegroPresentNativeUSDA-NRCS, 2013
NetherlandsPresentNativeUSDA-NRCS, 2013
NorwayPresentNativeUSDA-NRCS, 2013
PolandPresentNativeUSDA-NRCS, 2013
PortugalPresentNativeUSDA-NRCS, 2013
-AzoresPresentIntroducedUSDA-NRCS, 2013
-MadeiraPresentNativeUSDA-NRCS, 2013
RomaniaPresentNativeUSDA-NRCS, 2013
Russian FederationPresentPresent based on regional distribution.
-Northern RussiaPresentNativeUSDA-NRCS, 2013
-Southern RussiaPresentNativeUSDA-NRCS, 2013
SerbiaPresentNativeUSDA-NRCS, 2013
SlovakiaPresentNativeUSDA-NRCS, 2013
SloveniaPresentNativeUSDA-NRCS, 2013
SpainPresentNativeUSDA-NRCS, 2013
SwedenPresentNativeUSDA-NRCS, 2013
SwitzerlandPresentNativeUSDA-NRCS, 2013
UKUnconfirmed recordCAB Abstracts; USDA-NRCS, 2013
UkrainePresentNativeUSDA-NRCS, 2013
Yugoslavia (former)PresentNativeUSDA-NRCS, 2013

Oceania

AustraliaUnconfirmed recordCAB Abstracts; USDA-NRCS, 2013
-Australian Northern TerritoryPresentIntroducedWeeds of Australia, 2013Southern parts
-Lord Howe Is.PresentIntroduced Invasive PIER, 2014
-New South WalesWidespreadIntroduced Invasive Weeds of Australia, 2013
-QueenslandUnconfirmed recordCAB Abstracts; Weeds of Australia, 2013
-South AustraliaWidespreadIntroduced Invasive Weeds of Australia, 2013South-eastern South Australia
-TasmaniaUnconfirmed recordCAB Abstracts; Weeds of Australia, 2013
-VictoriaWidespreadIntroduced Invasive Weeds of Australia, 2013
-Western AustraliaPresentIntroducedWeeds of Australia, 2013South-western West Australia
French PolynesiaPresentIntroduced Invasive PIER, 2013; PIER, 2013Tahiti
New ZealandWidespreadIntroduced Invasive Webb et al., 1988
-Kermadec IslandsPresentIntroduced Invasive PIER, 2014
NiuePresentIntroducedGBIF, 2014
Norfolk IslandPresentIntroduced Invasive PIER, 2013

History of Introduction and Spread

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H. radicata was originally native to Morocco, where the oldest populations are still found. From there the species expanded its range in the late Quaternary via at least three migratory routes, the earliest of which was apparently to the south-western Iberian Peninsula, with subsequent movement to the central Mediterranean and elsewhere. It is now considered native throughout Europe (Ortiz et al., 2008). Ortiz et al. (2008) proposed that there were possibly two or more independent colonisations of the UK.

Later, H. radicata was almost certainly taken, either accidentally or deliberately, by European migrants to new colonies in North and South America, Asia, Australia and New Zealand. Some seeds may have been taken by migrants for medicinal or food purposes; others may have been inadvertently taken in hay or straw for livestock, in straw palliasses, or in vegetation used for packing household necessities. This spread was probably helped by an important change in ecological tolerance, allowing H. radicata, originally suited to humid Mediterranean woodlands, to invade more open temperate grasslands.

Introductions

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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Australia Europe 1873 Yes Australia’s Virtual Herbarium (2013); Royal Botanic Gardens Sydney (2004); Royal Botanic Gardens Sydney (2013) Probably accidental, first record, Camperdown, Victoria
Canada Europe Pre-1884 Yes Aarssen (1981) Probably accidental
China 2009 eFloras (2014); PIER (2014) Recorded in Yunnan – status uncertain according to eFloras, naturalised and invasive according to PIER
New Zealand Europe 1867 Yes Webb et al. (1988) Probably accidental

Habitat

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In its ancestral range in Morocco, H. radicata preferred humid Mediterranean woodlands (Ortiz et al., 2008). It has since expanded its range to include a wider variety of habitats; in particular, grasslands and waste places of various kinds have also become the natural home of H. radicata. It can be found along roadsides, in orchards, vineyards, landscaped areas and gardens, often as a lawn weed.

In the UK, H. radicata is primarily a plant of regularly cut or grazed neutral grasslands, of grassland on sandy soils, and of man-made habitats with bare soil. It is most often found in pastures and lawns, on roadside verges and banks, on fixed dunes, in cliff-top grasslands, in waste places in built-up areas and on raw soil (Turkington and Aarssen, 1983).

In New Zealand it is ‘abundant in waste places, pasture and modified tussock grassland through both islands and extending from sea-level to the upper level of vegetation on the mountains’ (Healy, 1992).

In Australia, Weeds of Australia (2013) described it as ‘possibly the most widely distributed weed in south-eastern Australia’, and ‘a very common weed of parks, gardens, footpaths, lawns, roadsides, disturbed sites, waste areas, cultivation and pastures,’ but commented that it is also common in natural habitats.

In British Columbia, H. radicata has been recorded from swamps, ditches, forest edges and clearings, on beaches and cliffs and in grazed pastures and grass/forb and sedge communities (Aarssen, 1981). It is rare in the Canadian prairies.

In California, CAL-IPC (2013) described H. radicta as invading sites relatively undisturbed by human activity, but more invasive and prevalent on disturbed sites such as grazed or burned lands, especially those in coastal areas. It is widespread and abundant in coastal terrace prairie and coastal bluff scrub, often one of the more dominant species.

In Japan, it is found in all temperate areas, often in grasslands (Doi et al., 2006).

H. radicata tolerates a wide range of soil texture and pH, having been found from light sand and gravel through to clay, and from soils with a pH of 3.9 to those with pH 8.6 (Turkington and Aarssen, 1983). It occurs on some of the driest soils in the UK, but in continental Europe it prefers moist, well-drained sites, although it is absent from sites subject to prolonged waterlogging. 

Habitat List

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CategorySub-CategoryHabitatPresenceStatus
Terrestrial
 
Terrestrial – ManagedManaged grasslands (grazing systems) Principal habitat
Disturbed areas Principal habitat
Rail / roadsides Principal habitat
Urban / peri-urban areas Principal habitat

Biology and Ecology

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Genetics

Recorded diploid counts for both British and Canadian plants are 2n=8 (Aarssen, 1981; Turkington and Aarssen, 1983). Panigrahi and Kammathy (1961, cited in Aarssen, 1991) reported occasional trisomics with 2n = 9 for Indian plants.

Reproductive biology

Ho (1964, cited in Aarssen, 1981) found that mature, flowering plants can be produced from seed in as little as 2 months under favourable conditions in British Columbia. According to several sources (Fryxel, 1957; Parker 1975), H. radicata is cross-pollinated and self-incompatible. Picó et al. (2004) observed that selfing dramatically reduced seed set, but the few selfed seeds produced were larger and had a greater chance of surviving to flowering than outcrossed seeds. This ability to self-fertilise may be important for isolated individuals that are the first to reach new habitats.

Flowering begins in response to long days, in May in British Columbia and in June in the UK, and continues until October or September (Salisbury, 1964; Aarssen, 1981). Although Salisbury (1964) claimed that ‘the flower heads close at night but open in daylight even when it is dull and cloudy’, Percival (1950) said that sunlight is necessary to stimulate the flowers to open in the morning, and that the flowers do not open in rain or if rain and sun alternate for about half an hour each. Once the flower is open it cannot close for at least 3 hours. In warm sunny conditions, flowers may stay open for about 3-4 hours, or up to 6-7 hours in cool cloudy conditions (Percival, 1950). Many insects visit the flowers, some to eat, and possibly disperse pollen whilst others feed on the nectar (and presumably disperse pollen at the same time) (Aarssen, 1981). The honey bee (Apis mellifera) is one of the major beneficiaries of the large amounts of pollen the flowers produce (Percival, 1950).

The fruit heads may total 60 or more on one plant but on average only about 20 are produced, and each one contains about 44 fruits (seeds) but sometimes as many as 136 (Salisbury, 1942). The ripe fruit is orange-brown in colour, 4-5 mm long with about 15 longitudinal ridges and a beak-like apex with a pappus of an outer ring of short simple hairs and an inner ring of feathery ones. The average weight is from 0.6-0.8 mg and germination ranges from 30 to 90% (Salisbury, 1964). Ho (1964, cited in Aarssen, 1981) estimated an annual production of 2329 achenes per plant over a 27 day period in British Columbia.

Soons et al. (2004) simulated wind dispersal of grassland plant seed (one species being H. radicata) and found that ‘autocorrelated turbulent fluctuations in vertical wind velocity are the key mechanism for long-distant dispersal.’ Dispersal distances are greatest under high wind velocity, when mechanically produced turbulent air movements are large. Under very low wind velocity conditions seeds are dispersed further when there is more surface heating, but never as far as when winds are strong.

Physiology and phenology

In the UK the species begins flowering in June and continues until September, usually with a flush in each of those two seasons (Salisbury, 1964). The flower heads in the first flush are often larger, nearly 4 cm across, whilst those of the autumn flush are often about 2.5 cm across. All the individual flowers in the flower head are strap-shaped and yellow but at the margins they have a greenish underside with a purplish tinge. Intermingled with the flowers are many tapering scales.

Ho (1964, cited in Aarssen, 1981) said that freshly harvested seeds did not need a period of dormancy before germination, that light is needed for germination and that seeds lost viability rapidly in dry storage. Immediately after harvest seeds gave 68% germination but after two months of dry storage, this percentage had fallen to 4%. Grime et al. (1981) also found that dry storage (in their case for 12 months at 5oC) reduced germination from 94% for fresh seed to 31%.

Hartemink et al. (2004) found that regular and continuous removal of flower buds of H. radicata from the onset of flowering until early October led to a 3-4 fold increase in the number of flower buds produced, an increase in the number of flowering stems and greater branching of the flower stems. In addition, when flowering was prevented, plants switched their resources to greater vegetative reproduction and they generated more new rosettes. Struik (1967) found that 20% of his sampled plants (in lawns and grazed pasture) were in clusters of two to six individuals, presumably originating by vegetative reproduction of a single plant.

The rosette leaves can grow very close to the ground, which protects them and buds from mowing or grazing. The perennial roots grow far below the root depth of neighbouring species in lawns, which may explain its high mineral and trace element content (Fagan and Watkins, 1932; Coop et al., 1953; Struik, 1967) as well as its tolerance of drought (Turkington and Aarenssen, 1983). The small epidermal cells of the leaves and the large multicellular hairs (Ormrod and Renney, 1968) may also assist in its drought tolerance. In lawns and possibly elsewhere the plant is often multi-crowned, and the crown may extend 2-3 cm below the ground surface (Healy, 1962).

Longevity

H. radicata is a relatively short-lived species which lives for up to two seasons (de Kroon et al., 1987; Fone, 1989). Plants can overwinter as green leafy rosettes or, in colder climates, above-ground parts die back, leaving perennating buds at ground level (Aarssen, 1981). The seeds do not seem to persist for long in the soil seed bank.

Population size and structure

Ridley (1930, cited in Aarssen, 1981) claimed that H. radicata has been known to displace every other plant in pastures, including white clover (Trifolium repens). Ho (1964, cited in Aarssen, 1981) found little reduction in top and root development or number of seeds produced when plants were growing in grass compared with plants growing alone.

H. radicata may exert allelopathic effects on other grassland species (Aarseen, 1981). Root leachates were found to reduce shoot dry weight of several grassland species (Newman and Rovira. 1975). Leaf extracts caused a significant decline in germination rate and seedling shoot length in Agrostis tenuis (now known as A. capillaris). The same authors found that H. radicata is autotoxic, its own exudates inhibiting its growth by more than that of neighbouring plants, which may explain why it is often found as isolated individuals or in small clusters rather than forming large patches or pure stands (Aarssen, 1981).

Guthrie-Smith (1953) observed H. radicata to be one of the early colonisers after fire in grassland in New Zealand.

Nutrition

Coop et al. (1953) analysed the chemical components of H. radicata in New Zealand: protein 10-15%, fibre 10-20%, calcium 1-2%, phosphorus 0.15-0.5% and copper 5-10 ppm, on a dry matter basis. Grace and Scott (1974) and Turkington and Aarssen (1983) presented further information on the concentration of mineral elements in New Zealand and British plant material.

Brun et al. (2003) experimented with different levels of copper added to soil and measured its effects on H. radicata and other species found in European vineyards, where high concentrations of copper are found in the soil surface due to the repeated use of copper-based fungicides for protection against vine downy mildew (Plasmopara viticola). High concentrations of copper in the soil led to lower survival, lower total plant biomass, a delay in flowering and fruiting, and low seed set in the five species tested. H. radicata was especially sensitive to high concentrations of copper in the soil, although it still produced seeds at all levels of copper except the highest tested (400 mg kg-1 of added copper, making the total copper load in the soil 558 mg kg-1).

Associations

Turkington and Aarssen (1983) presented a large table of species associated with H. radicata in the Sheffield area in England, UK, and also listed many communities in which it occurs. In the Sheffield area it was associated with 197 other species, almost all species of open grassland like Agrostis capillaris, Anthoxanthum odoratum, Festuca rubra, Holcus lanatus, Lolium perenne and Trifolium spp.

Notes on Natural Enemies

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The stalks of H. radicata often show gall swellings caused by the hymenopteran insect Aulax hypochaeridis. Guthrie-Smith (1953) observed broomrape (Orobanche minor) attached to the roots of H. radicata in New Zealand. Both Aarssen (1981) and Turkington and Aarssen (1983) listed invertebrate species that parasitise or feed on H. radicata, and Turkington and Aarssen (1983) also listed fungi and viruses found on H. radicata (see Natural Enemies table).

Means of Movement and Dispersal

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Natural dispersal (non-biotic)

The large numbers of wind-dispersed achenes (seeds) ensure their wide dispersal from the parent plants.

Vector transmission (biotic)

Ridley (1930, cited in Aarssen, 1981) reported that birds are known to disperse the fruit by attachment to their feet and plumage, and ants have been observed carrying seeds of H. radicata.

Accidental introduction

Seeds may have been inadvertently transported to the Americas, Asia, Australia and New Zealand by European migrants as contaminants of grass seed, straw or hay for livestock, straw palliasses, or vegetation used for packing household necessities.

Intentional introduction

Seeds may have also been taken by European migrants to North and South America, Asia, Australia and New Zealand deliberately for medicinal or food purposes.

Impact Summary

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CategoryImpact
Economic/livelihood Positive and negative

Economic Impact

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The consumption of H. radicata apparently causes stringhalt, a disease of horses, at least in Australia and New Zealand (Cahill et al., 1995). Stringhalt refers to a myoclonic affliction of one or both hindlimbs seen as spasmodic overflexion of the joints (Merck Veterinary Manual, 2013). MacKay et al. (2013) observed dose-dependent cytotoxicity when they exposed cultured cells of neural tissue to extracts of H. radicata.

Time, energy and expense are spent by gardeners in controlling H. radicata when it invades lawns and golf courses, and by municipal councils in killing it on roadsides and waste places around towns and cities.

Risk and Impact Factors

Top of page Invasiveness
  • Invasive in its native range
  • Proved invasive outside its native range
  • Has a broad native range
  • Abundant in its native range
  • Is a habitat generalist
  • Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
  • Pioneering in disturbed areas
  • Benefits from human association (i.e. it is a human commensal)
  • Fast growing
  • Has high reproductive potential
  • Has propagules that can remain viable for more than one year
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Difficult to identify/detect as a commodity contaminant

Uses

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Economic value

Modified slightly from Aarssen (1981):

In New Zealand and Australia H. radicata has been considered one of the most palatable species occurring in tussock grassland and, being more productive than other herbs, is therefore useful to livestock (Coop et al., 1953; Healy, 1962). It often invades thin, overgrazed and under-fertilised pastures and thus tends to offset the reduced carrying capacity of these pastures (Sewell, 1950; Lamp and Collett, 1976). Sheep preferentially eat H. radicata before any other herb or grass (Struik, 1967; Hughes, 1975). H. radicata is superior to many grasses in nutritive value and is comparable to white clover, being high in protein, low in fibre, exceptionally high in calcium and quite good for copper content (Coop et al., 1953). It is also rich in sulphur, phosphorus (Begg and Freney, 1960) and chloride (Fagan and Watkins, 1932). Highest nutritive value occurs in spring and winter months (Coop et al., 1953). Stapledon (1948) suggested sowing H. radicata in grazed grasslands along with a non-aggressive grass.

The shoots of H. radicata are eaten by sheep (Ovis ovis), pigs (Sus scrofula), snowshoe hares (Lepus americanus) (Radwan and Campbell, 1968), slugs (Healy 1962), snails (Helix aspersa (Weiner, 1993), birds and ants. Pigs uproot the plants and feed on the roots.

Social benefit

H. radicata leaves have been used as in salads or cooked as a vegetable (PFAF, 2013). Leaves can be rather bitter, although young leaves are milder. The roots can also be dried and ground and used as a coffee substitute.

The plant also has properties useful to herbalists and for natural medicines. Jamuna et al. (2012) described its use in traditional medical practice for its anticancer, anti-inflammatory, anti-diuretic and hepatoprotective activity, and also in treating kidney problems. In Nilgiris (Tamil Nadu, India), traditional healers prescribed H. radicata for wound healing and skin diseases caused by pathogens. Jamuna et al. (2012) also investigated the antibiotic properties of roots and leaves and found that ‘the antibacterial activity of the methanolic extracts of both parts was comparable to that of the standard drug, ampicillin.’

Similarities to Other Species/Conditions

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H. radicata can be confused with other rosette weeds with similar bright yellow flowers in the same family, including H. glabra, Crepis capillaris, Leontodon autumnalis and the true dandelion Taraxacum officinale (Aarssen, 1981).Aarssen (1981) provided a key for separating these species (but did not include Crepis capillaris), and Healy (1992) provided a useful guide to distinguishing these species. In essence, in the rosette stage H. radicata has rounded leaf lobes, hairs on the leaf margins, a thick, rough leaf surface, and simple leaf hairs. When flowering, it has leafless branched flower stalks and large flower heads. The stalks of both H. radicata and H. glabra often show gall swellings caused by the hymenopteran insect Aulax hypochaeridis.

 

Prevention and Control

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Physical/mechanical control

Ploughing and cultivating for one or two years before reseeding gave effective control (Aarssen, 1981, quoting the Canadian Dept. of Agriculture). Pigs may exert some control by uprooting plants, but by disturbing the ground they probably aid rapid reinfestation by H. radicata.

The taproot must be cut several inches below the crown and removed to stop it resprouting (DiTomaso et al., 2013).

Chemical control

In Canada, Turkington and Aarssen (1983) mentioned that H. radicata was ‘resistant’ to atrazine and dalapon and moderately ‘resistant’ to paraquat, asulam, picloram and other herbicides. However, they suggested that adequate selective control can be achieved in grassland or turfgrasses with MCPA, 2,4-D, or mecoprop.

DiTomaso et al. (2013) presented a long list of herbicides that can be used to control H. radicata in different circumstances. Some of these are selective and will not affect grasses; others will kill any green plant they contact. The list includes 2,4-D, aminocyclopyrachlor, aminopyralid, chlorsulfuron, clopyralid, dicamba, fluroxypyr, glyphosate, hexazinone, imazapyr, metsulfuron, picloram, sulfometuron and triclopyr.

Control by utilization

The species is considered highly palatable and nutritious to sheep and cattle, although the rosette leaves can be strongly appressed to the ground and may sometimes be hard for livestock to access.

Livestock grazing benefits the growth and reproduction of H. radicata. Struik (1967) studied the size and growth of H. radicata in mown and unmown lawns and in heavily and lightly grazed pastures in New Zealand. Dry weight per plant was least in the mown lawns and greatest in grazed pasture; the greatest vegetative weight was achieved under heavy grazing and the highest reproductive weight under lax grazing. Relative weight of leaves and roots decreased and relative weight of floral organs increased with decreasing stand defoliation. Relative root biomass decreased with increasing relative weight of floral organs. 

References

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Links to Websites

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WebsiteURLComment
GISD/IASPMR: Invasive Alien Species Pathway Management Resource and DAISIE European Invasive Alien Species Gatewayhttps://doi.org/10.5061/dryad.m93f6Data source for updated system data added to species habitat list.

Contributors

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: Original text by:

Ian Popay, consultant, New Zealand, with the support of Landcare Research.

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