Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Lolium perenne
(perennial ryegrass)

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Datasheet

Lolium perenne (perennial ryegrass)

Summary

  • Last modified
  • 19 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Pest
  • Host Plant
  • Preferred Scientific Name
  • Lolium perenne
  • Preferred Common Name
  • perennial ryegrass
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Monocotyledonae
  • Summary of Invasiveness
  • Lolium grasses have many weedy characteristics. They are capable of adapting rapidly to their environment, produce large amounts of seed, and are easily dispersed, usually by humans. The perennial ryegrass, ...

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Pictures

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PictureTitleCaptionCopyright
Lolium perenne (perennial ryegrass); plants as weeds in maize crop
TitleHabit
CaptionLolium perenne (perennial ryegrass); plants as weeds in maize crop
Copyright©Trevor James/Hamilton, New Zealand
Lolium perenne (perennial ryegrass); plants as weeds in maize crop
HabitLolium perenne (perennial ryegrass); plants as weeds in maize crop©Trevor James/Hamilton, New Zealand
Lolium perenne (perennial ryegrass); vegetative plant. New Zealand. March 2007
TitleVegetative plant
CaptionLolium perenne (perennial ryegrass); vegetative plant. New Zealand. March 2007
Copyright©Trevor James/Hamilton, New Zealand
Lolium perenne (perennial ryegrass); vegetative plant. New Zealand. March 2007
Vegetative plantLolium perenne (perennial ryegrass); vegetative plant. New Zealand. March 2007©Trevor James/Hamilton, New Zealand
Lolium perenne (perennial ryegrass) collar zone at base of leaf blade showing ligule
TitleLigule
CaptionLolium perenne (perennial ryegrass) collar zone at base of leaf blade showing ligule
Copyright©Trevor James/Hamilton, New Zealand
Lolium perenne (perennial ryegrass) collar zone at base of leaf blade showing ligule
LiguleLolium perenne (perennial ryegrass) collar zone at base of leaf blade showing ligule©Trevor James/Hamilton, New Zealand
Lolium perenne (perennial ryegrass); plant with inflorescence
TitlePlant with inflorescence
CaptionLolium perenne (perennial ryegrass); plant with inflorescence
Copyright©Trevor James/Hamilton, New Zealand
Lolium perenne (perennial ryegrass); plant with inflorescence
Plant with inflorescenceLolium perenne (perennial ryegrass); plant with inflorescence©Trevor James/Hamilton, New Zealand
Lolium perenne (perennial ryegrass); inflorescence
TitleInflorescence
CaptionLolium perenne (perennial ryegrass); inflorescence
Copyright©Trevor James/Hamilton, New Zealand
Lolium perenne (perennial ryegrass); inflorescence
InflorescenceLolium perenne (perennial ryegrass); inflorescence©Trevor James/Hamilton, New Zealand
Lolium perenne (perennial ryegrass); close-up of inflorescence
TitleInflorescence
CaptionLolium perenne (perennial ryegrass); close-up of inflorescence
Copyright©Trevor James/Hamilton, New Zealand
Lolium perenne (perennial ryegrass); close-up of inflorescence
InflorescenceLolium perenne (perennial ryegrass); close-up of inflorescence©Trevor James/Hamilton, New Zealand

Identity

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Preferred Scientific Name

  • Lolium perenne L.

Preferred Common Name

  • perennial ryegrass

International Common Names

  • English: English ryegrass; Italian ryegrass; perennial rye grass
  • Spanish: ballico perenne; raigras ingles; vallico
  • French: ivraie vivace; ray-grass anglais
  • Portuguese: azevem-vivaz; gazao

Local Common Names

  • : cesped ingles; raygrass
  • : eavers; ray grass
  • : gazun
  • : hei mei cao
  • Germany: Deutsches Weidelgras; Englisches Raygras
  • Italy: loglio inglese; loglio perenne; loietto inglese
  • Japan: hosomugi
  • Korea, Republic of: homilpul
  • Netherlands: engels Raaigras
  • South Africa: meerjarige raaisgra
  • Sweden: engelski rajgras; engelskt Rajgraes

EPPO code

  • LOLPE (Lolium perenne)

Summary of Invasiveness

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Lolium grasses have many weedy characteristics. They are capable of adapting rapidly to their environment, produce large amounts of seed, and are easily dispersed, usually by humans. The perennial ryegrass, L. perenne, is native to central Asia, the Middle East, North Africa and southern Europe, from Bulgaria in the east to France in the west. It was introduced by early European pastoralists to many corners of their earlier empires, including North America, Australasia, South Africa and elsewhere. As a result it has been sown in many countries and has become extremely widespread both as a cultivated species for livestock grazing and for fodder (as hay or silage). It is also a useful cover crop for soil stabilisation and pasture improvement, as well as an excellent grass for lawns and turf.

From sown pastures it has spread to occupy footpaths, roadsides, tracks, waste places, sand dunes and river beds. In New Zealand and Australia, the species is considered an environmental weed and in Australia the grass impacts the threatened spiny peppercress (Lepidium aschersonii) and the vulnerable red darling pea (Swainsona plagiotropis). It is also a principal weed species in endangered tableland basalt forests and fuzzy box (Eucalyptus conica) woodlands in various parts Australia.

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Monocotyledonae
  •                     Order: Cyperales
  •                         Family: Poaceae
  •                             Genus: Lolium
  •                                 Species: Lolium perenne

Notes on Taxonomy and Nomenclature

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Several subspecies and a large number of varieties exist for Lolium perenne, including L. perenne subsp. multiflorum, L. perenne subsp. remotum and L. perenne var. cristatum (The Plant List, 2013). L. perenne itself shows considerable variation in growth form, from erect, few-tillered individuals to prostrate compact cushions with many vegetative shoots. Beddows (1967) describes several forms with abnormal inflorescences and abnormal spikelet development. L. perenne has also been intensively bred for many years in different countries and many improved varieties of both diploid and tetraploid forms are now available for pasture or turf.

L. perenne freely crosses with Lolium multiflorum (Italian ryegrass); producing fertile hybrids (L. x hybridum) with intermediate characteristics. It also forms hybrids with species of Schedonorus (formerly Festuca) such as S. arundinaceus, S. giganteus and S. pratensis (ITIS, 2013; The Plant List, 2013).

Description

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L. perenne does not produce stolons or rhizomes, its shoot buds arise at or near the soil level in young plants but may develop from higher nodes in large single plants. The nodal roots are variable, and may be white, thick, glossy, straight, unbranched and covered with root hairs or more slender and soon becoming fibrous (Beddows, 1967). The initial stem within the germinating seed is about 2 mm long and 2.8 mm in diameter and all the leaves, tillers and roots originate from this. Primary and adventitious roots arise from the base of the embryo (Soper and Mitchell, 1956). Beddows (1958) described L. perenne as a hemicryptophyte with a semi-rosette form before head emergence.

The following detailed description is adapted from Clayton et al. (2013).

Habit: perennial grass; caespitose. Culms erect, or decumbent; 30–90 cm long. Leaf-sheath oral hairs lacking. Leaf-sheath auricles falcate. Ligule an eciliate membrane. Leaf-blades 3–20 cm long; 2–6 mm wide.

Inflorescence: Composed of racemes. Racemes 1; single; bilateral; 4–30 cm long. Rhachis semiterete. Spikelet packing adaxial; 1 their length apart; regular; 2 -rowed.

Spikelets appressed; solitary. Fertile spikelets sessile.

Fertile spikelets: comprising 4–14 fertile florets; with diminished florets at the apex. Spikelets oblong; laterally compressed; 7–20 mm long; breaking up at maturity; disarticulating below each fertile floret.

Glumes: One the lower absent or obscure; persistent; shorter than spikelet; similar to fertile lemma in texture. Upper glume lanceolate; coriaceous; without keels; 5–7 -veined. Upper glume surface smooth. Upper glume apex obtuse.

Florets: Fertile lemma oblong; 5–7 mm long; coriaceous; without keel; 5 -veined. Lemma apex obtuse; muticous. Palea keels scaberulous. Apical sterile florets resembling fertile though underdeveloped.

Flower: Ovary glabrous.

Fruit: Hilum linear.

Plant Type

Top of page Grass / sedge
Perennial
Seed propagated

Distribution

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L. perenne is native to central Asia, the Middle East, North Africa and southern Europe, from Bulgaria in the east to France in the west. It was introduced by early European pastoralists to many corners of their earlier empires, including North America, Australasia, South Africa and elsewhere. It is now found in all the USA from Alaska to Hawaii, and was present in Virginia from as early as 1782 (Sullivan, 1992). It occurs in all the States of Australia and in many other countries. It has also been found in very remote southern sub-Antarctic islands, including the Crozet Islands, Possession Island and the Kerguelen Islands (Australian Antarctic Division, 2013).

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

AfghanistanPresentNativeUSDA-ARS, 2013
ArmeniaPresentNativeUSDA-ARS, 2013
AzerbaijanPresentNativeUSDA-ARS, 2013
Chagos ArchipelagoPresentIntroducedPIER, 2013
ChinaWidespreadIntroducedeMonocot, 2013North-central, south-central, southeast
-Hong KongPresentIntroducedPIER, 2013
Georgia (Republic of)PresentNativeUSDA-ARS, 2013
IndiaPresentIntroducedUSDA-ARS, 2013
IranPresentNativeUSDA-ARS, 2013
IraqPresentNativeUSDA-ARS, 2013
IsraelPresentNativeUSDA-ARS, 2013
JapanPresentIntroducedeMonocot, 2013
JordanPresentNativeUSDA-ARS, 2013
KazakhstanPresentIntroducedeMonocot, 2013
Korea, Republic ofPresentIntroducedeMonocot, 2013
KyrgyzstanPresentIntroducedeMonocot, 2013
LebanonPresentNativeUSDA-ARS, 2013
MalaysiaPresentIntroducedeMonocot, 2013
NepalPresentIntroducedeMonocot, 2013
PakistanPresentNativeUSDA-ARS, 2013
Saudi ArabiaPresentNativeUSDA-ARS, 2013
Sri LankaPresentIntroducedeMonocot, 2013
SyriaPresentNativeUSDA-ARS, 2013
TaiwanPresentIntroducedPIER, 2013
TurkeyPresentNativeUSDA-ARS, 2013
TurkmenistanPresentIntroducedeMonocot, 2013
UzbekistanPresentIntroducedeMonocot, 2013
YemenPresentNativeeMonocot, 2013

Africa

AlgeriaPresentNativeUSDA-ARS, 2013
EgyptPresentNativeUSDA-ARS, 2013
EritreaPresentIntroducedeMonocot, 2013
LesothoPresentNativeUSDA-ARS, 2013
LibyaPresentNativeUSDA-ARS, 2013
MauritaniaPresentIntroducedeMonocot, 2013
MauritiusPresentIntroducedUSDA-ARS, 2013
MoroccoPresentNativeUSDA-ARS, 2013
RéunionPresentIntroducedUSDA-ARS, 2013
Rodriguez IslandPresentIntroducedPIER, 2013
South AfricaPresentIntroducedeMonocot, 2013Cape Provinces, Free State, KwaZulu-Natal, Lesotho, Northern Provinces
Spain
-Canary IslandsPresentNativeUSDA-ARS, 2013
TunisiaPresentNativeUSDA-ARS, 2013
ZimbabwePresentIntroducedeMonocot, 2013

North America

CanadaPresentPresent based on regional distribution.
-AlbertaPresentIntroducedUSDA-NRCS, 2013
-British ColumbiaPresentIntroducedUSDA-NRCS, 2013
-ManitobaPresentIntroducedUSDA-NRCS, 2013
-New BrunswickPresentIntroducedUSDA-NRCS, 2013
-Newfoundland and LabradorPresentIntroducedUSDA-NRCS, 2013
-Northwest TerritoriesPresentIntroducedUSDA-NRCS, 2013
-Nova ScotiaPresentIntroducedUSDA-NRCS, 2013
-NunavutPresentIntroducedUSDA-NRCS, 2013
-OntarioPresentIntroducedUSDA-NRCS, 2013
-Prince Edward IslandPresentIntroducedUSDA-NRCS, 2013
-QuebecPresentIntroducedUSDA-NRCS, 2013
-SaskatchewanPresentIntroducedUSDA-NRCS, 2013
-Yukon TerritoryPresentIntroducedUSDA-NRCS, 2013
GreenlandPresentIntroducedUSDA-NRCS, 2013
MexicoPresentIntroducedUSDA-ARS, 2013
Saint Pierre and MiquelonPresentIntroducedUSDA-NRCS, 2013
USAPresentPresent based on regional distribution.
-AlabamaPresentIntroducedUSDA-NRCS, 2013
-AlaskaPresentIntroducedUSDA-NRCS, 2013
-ArizonaPresentIntroducedUSDA-NRCS, 2013
-ArkansasPresentIntroducedUSDA-NRCS, 2013
-CaliforniaPresentIntroducedUSDA-NRCS, 2013
-ColoradoPresentIntroducedUSDA-NRCS, 2013
-ConnecticutPresentIntroducedUSDA-NRCS, 2013
-DelawarePresentIntroducedUSDA-NRCS, 2013
-District of ColumbiaPresentIntroducedUSDA-NRCS, 2013
-FloridaPresentIntroducedUSDA-NRCS, 2013
-GeorgiaPresentIntroducedUSDA-NRCS, 2013
-HawaiiPresentIntroducedUSDA-NRCS, 2013
-IdahoPresentIntroducedUSDA-NRCS, 2013
-IllinoisPresentIntroducedUSDA-NRCS, 2013
-IndianaPresentIntroducedUSDA-NRCS, 2013
-IowaPresentIntroducedUSDA-NRCS, 2013
-KansasPresentIntroducedUSDA-NRCS, 2013
-KentuckyPresentIntroducedUSDA-NRCS, 2013
-LouisianaPresentIntroducedUSDA-NRCS, 2013
-MainePresentIntroducedUSDA-NRCS, 2013
-MarylandPresentIntroducedUSDA-NRCS, 2013
-MassachusettsPresentIntroducedUSDA-NRCS, 2013
-MichiganPresentIntroducedUSDA-NRCS, 2013
-MinnesotaPresentIntroducedUSDA-NRCS, 2013
-MississippiPresentIntroducedUSDA-NRCS, 2013
-MissouriPresentIntroducedUSDA-NRCS, 2013
-MontanaPresentIntroducedUSDA-NRCS, 2013
-NebraskaPresentIntroducedUSDA-NRCS, 2013
-NevadaPresentIntroducedUSDA-NRCS, 2013
-New HampshirePresentIntroducedUSDA-NRCS, 2013
-New JerseyPresentIntroducedUSDA-NRCS, 2013
-New MexicoPresentIntroducedUSDA-NRCS, 2013
-New YorkPresentIntroducedUSDA-NRCS, 2013
-North CarolinaPresentIntroducedUSDA-NRCS, 2013
-North DakotaPresentIntroducedUSDA-NRCS, 2013
-OhioPresentIntroducedUSDA-NRCS, 2013
-OklahomaPresentIntroducedUSDA-NRCS, 2013
-OregonPresentIntroducedUSDA-NRCS, 2013
-PennsylvaniaPresentIntroducedUSDA-NRCS, 2013
-Rhode IslandPresentIntroducedUSDA-NRCS, 2013
-South CarolinaPresentIntroducedUSDA-NRCS, 2013
-South DakotaPresentIntroducedUSDA-NRCS, 2013
-TennesseePresentIntroducedUSDA-NRCS, 2013
-TexasPresentIntroducedUSDA-NRCS, 2013
-UtahPresentIntroducedUSDA-NRCS, 2013
-VermontPresentIntroducedUSDA-NRCS, 2013
-VirginiaPresentIntroducedUSDA-NRCS, 2013
-WashingtonPresentIntroducedUSDA-NRCS, 2013
-West VirginiaPresentIntroducedUSDA-NRCS, 2013
-WisconsinPresentIntroducedUSDA-NRCS, 2013
-WyomingPresentIntroducedUSDA-NRCS, 2013

Central America and Caribbean

Costa RicaPresentIntroducedUSDA-ARS, 2013
GuatemalaPresentIntroducedUSDA-ARS, 2013
HondurasPresentIntroducedUSDA-ARS, 2013
PanamaPresentIntroducedUSDA-ARS, 2013

South America

ArgentinaPresentIntroducedUSDA-ARS, 2013
BoliviaPresentIntroducedUSDA-ARS, 2013
BrazilPresentIntroducedUSDA-ARS, 2013
ChilePresentIntroducedUSDA-ARS, 2013
EcuadorPresentIntroducedUSDA-ARS, 2013
Falkland IslandsLocalisedIntroducedFalklands Conservation, 2012
French GuianaPresentIntroducedUSDA-ARS, 2013
PeruPresentIntroducedUSDA-ARS, 2013
UruguayPresentIntroducedUSDA-ARS, 2013

Europe

AlbaniaPresentNativeeMonocot, 2013
AustriaPresentNativeeMonocot, 2013
BelarusPresentNativeeMonocot, 2013
BelgiumPresentNativeeMonocot, 2013
BulgariaPresentNativeFitter et al., 2013
CroatiaPresentNativeUSDA-ARS, 2013
CyprusPresentNativeeMonocot, 2013
Czech RepublicPresentNativeUSDA-ARS, 2013
Czechoslovakia (former)PresentNativeeMonocot, 2013
DenmarkPresentNativeeMonocot, 2013
FinlandPresentNativeeMonocot, 2013
FrancePresentNativeeMonocot, 2013
-CorsicaPresentNativeFitter et al., 2013
GermanyPresentNativeeMonocot, 2013
GreecePresentNativeeMonocot, 2013
HungaryPresentNativeeMonocot, 2013
IcelandPresentNativeeMonocot, 2013
IrelandPresentNativeeMonocot, 2013
ItalyPresentNativeeMonocot, 2013
LuxembourgPresentNativeFitter et al., 2013
MoldovaPresentNativeUSDA-ARS, 2013
NetherlandsPresentNativeeMonocot, 2013
NorwayPresentNativeeMonocot, 2013
PolandPresentNativeeMonocot, 2013
PortugalPresentNativeeMonocot, 2013
-AzoresPresentNativeeMonocot, 2013
-MadeiraPresentNativeUSDA-ARS, 2013
RomaniaPresentNativeeMonocot, 2013
Russian FederationPresentIntroducedeMonocot, 2013
-Central RussiaPresentIntroducedeMonocot, 2013
-Northern RussiaPresentIntroducedeMonocot, 2013
-Southern RussiaPresentIntroducedeMonocot, 2013
-Western SiberiaPresentIntroducedeMonocot, 2013
SerbiaPresentNativeUSDA-ARS, 2013
SlovakiaPresentNativeUSDA-ARS, 2013
SloveniaPresentNativeUSDA-ARS, 2013
SpainPresentNativeeMonocot, 2013
SwedenPresentNativeeMonocot, 2013
SwitzerlandPresentNativeeMonocot, 2013
UKPresentNativeeMonocot, 2013
UkrainePresentIntroducedeMonocot, 2013

Oceania

AustraliaWidespreadIntroduced Invasive eMonocot, 2013
-Australian Northern TerritoryPresentIntroducedeMonocot, 2013
-New South WalesWidespreadIntroducedeMonocot, 2013
-QueenslandPresentIntroducedeMonocot, 2013
-South AustraliaWidespreadIntroducedeMonocot, 2013
-TasmaniaWidespreadIntroducedeMonocot, 2013
-VictoriaWidespreadIntroducedeMonocot, 2013
-Western AustraliaWidespreadIntroducedeMonocot, 2013
New CaledoniaPresentIntroduced Invasive USDA-ARS, 2013
New ZealandWidespreadIntroduced Invasive eMonocot, 2013
Papua New GuineaPresentIntroducedeMonocot, 2013

History of Introduction and Spread

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Mabberley (1997) suggests that L. perenne was ‘probably the first grass deliberately sown for pastures’. As a result it has been sown in many countries and has become extremely widespread both as a cultivated species for livestock grazing and for fodder (as hay or silage), and as a useful cover crop for soil stabilisation and pasture improvement, as well as an excellent grass for lawns and turf. It has probably been cultivated in England for about 300 years, and from there colonists took it to the USA, South Africa, Australasia and elsewhere (Hubbard, 1984). It was deliberately planted in many of these areas and in some places it has invaded native environments and can threaten native species.

The cultivated form of L. perenne has been described as a ‘camp-follower’ of man (Jenkin, 1951; 1959; Beddows, 1967), and to have a more southerly origin than the highly tillered, late-heading types found in the best old (English) grazing pastures.

Introductions

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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Australia 1873 Escape from confinement or garden escape (pathway cause) Yes CHAH (2014); Council of Heads of Australasian Herbaria (2013) Victoria
New Zealand UK early 1800s Escape from confinement or garden escape (pathway cause) Yes CHAH (2014); Council of Heads of Australasian Herbaria (2013) Growing 'admirably' in 1838
USA Europe 1782 Escape from confinement or garden escape (pathway cause) Yes Frakes (1973); Gould and Shaw (1983); Sullivan (1992) A good producer in Virginia

Risk of Introduction

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The species has already been introduced to many temperate countries and to higher altitude regions of tropical countries. It could be introduced to yet more places, but as a grass renowned for its productivity, it has probably been tested for its ability to grow almost anywhere. For example, attempts have been made to grow the grass in higher altitude pastures in Kenya but it did not establish successfully, being susceptible to competition from tropical grasses like Cenchrus clandestinus (formerly Pennisetum clandestinum) (Clayton, 1973; Orodho, 2013).

Habitat

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It is a plant of heath and shrubland, riparian habitats, freshwater wetlands and coastal beaches (PIER, 2014). In the UK, L. perenne has been widely used in the sowing down of leys for hay production for many years, and has thus become widely naturalised (Beddows, 1967). From these pastures it has become a common component of footpaths and roadsides both in the UK and elsewhere.

L. perenne is also a principal weed species in endangered tableland basalt forests and fuzzy box (Eucalyptus conica) woodlands in various parts of New South Wales, Australia (University of Queensland, 2013). In Western Australia, it grows on granite outcrops, in swamps, and along roadsides between Perth and Albany. It is also a weed of waterways and wetlands in the cooler and wetter areas of south-western Western Australia (University of Queensland, 2013).

It only occurs in upland pastures where phosphate and lime have been applied. In Hawaii, it is naturalized and common in grasslands and pastures (PIER, 2014). Beddows (1967) suggests annual rainfall of about 90 cm or a fairly high water table as desirable for its growth. 

In the United States, Sullivan (1992) notes that it is adapted to a wide range of soil types and drainage conditions, including wet or temporarily flooded areas. It can grow in areas up to 2000 m.

Habitat List

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CategoryHabitatPresenceStatus
Terrestrial-managed
Cultivated / agricultural land Secondary/tolerated habitat Natural
Disturbed areas Secondary/tolerated habitat Natural
Managed grasslands (grazing systems) Principal habitat Productive/non-natural
Rail / roadsides Secondary/tolerated habitat Natural
Urban / peri-urban areas Secondary/tolerated habitat Natural
Terrestrial-natural/semi-natural
Natural forests Present, no further details Harmful (pest or invasive)

Hosts/Species Affected

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The threatened spiny peppercress (Lepidium aschersonii) and the red darling pea (Swainsona plagiotropis) have both been reported as being threatened by L. perenne (University of Queensland, 2013). 

A dense, uniform sward of L. perenne provides a very effective barrier to the germination and establishment of many common pasture weeds such as thistles (Popay and Medd, 1995).

Biology and Ecology

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Genetics

The chromosome number is reported to be 2n=14, but tetraploid plants have been artificially produced with colchicine (Beddows, 1967). The tetraploids have slightly longer, wider and thicker leaves, fewer, more robust tillers, and larger spikelets, florets, pollen grains and caryopses. They are also more winter hardy and rust resistant. Initially these tetraploids were no more productive than diploids, but plant breeding has led to more productive cultivars, which are available commercially. These are more palatable to livestock than diploids, but require more care in their maintenance to prevent overgrazing or treading damage (Agriseeds, 2013). 

Reproductive Biology

The climatic requirements for inflorescence development show marked regional differences (Beddows, 1967). Varieties from more northern climates (in the Northern Hemisphere) require exposure to winter conditions of cold or short-days followed by photoperiods of 13 hours or more. By contrast, Mediterranean varieties have little or no need of cold or short days and floral initiation can occur during the short photoperiods of winter or early spring (9-10 hours). 

The first spikelets to have open flowers are the apical and third or fourth below the apex of the inflorescence, and in these anthesis begins with the lowest one or two florets in the spikelet. As the paleas separate the two feather-like stigmas emerge laterally and almost simultaneously the anthers are raised up on the elongating filaments until their weight becomes too great and they become pendulous (Beddows, 1967).

Exsertion of stigmas and anthers does not occur on dull overcast mornings but if the sun breaks through soon after midday anthesis is likely to follow, otherwise flowering is delayed until the first subsequent morning that provides suitable conditions (Beddows, 1967).

The caryopses (‘fruits’ or ‘seeds’) ripen in 4-5 weeks and the seeds readily separate from each other and the rhachis, to which the upper glumes remain attached. The caryopses show no resting or after-ripening phase so that germination can take place immediately (Beddows, 1967).

Physiology and Phenology

L. perenne does not produce stolons or rhizomes, its shoot buds arise at or near the soil level in young plants but may develop from higher nodes in large single plants. The nodal roots are variable, and may be white, thick, glossy, straight, unbranched and covered with root hairs or more slender and soon becoming fibrous (Beddows, 1967). The initial stem within the germinating seed is about 2 mm long and 2.8 mm in diameter and all the leaves, tillers and roots originate from this. Primary and adventitious roots arise from the base of the embryo (Soper and Mitchell, 1956). Beddows (1958) described L. perenne as a hemicryptophyte with a semi-rosette form before head emergence.

Individual shoots are annual or winter-annual, depending on the time taken to develop and mature their inflorescences. The seeds of L. perenne do not seem to persist for long in the soil. Roberts (1986) found that when seeds were incorporated into the soil, very few emerged after the first flush, which occurred soon after sowing in September in the UK.

L. perenne is most productive in spring and autumn. If spring grazing is hard enough to limit flower head production without damaging vegetative growth then this can prolong the spring grazing season (Waller and Sale, 2001). In dry summers it can become dormant and if overgrazed at that time of the year the grass may not survive to regrow in autumn. It may not survive very cold winters (minus 6oC or less; Cool et al., 2004).

In the UK, the relative growth rate of seedlings of L. perenne ranges from less than 0.03 g day-1 in winter to over 0.2 g day-1 in summer, corresponding to a range in net assimilation rate of 0.10 to 1.00 mg cm-2 day-1. The conversion of light energy falls from about 15% in winter to only 2-3% in summer because light saturation of photosynthesis occurs at about 3000-3500 feet - candles (32291 – 37673 lux) (Beddows, 1967). The efficiency of light conversion by a complete crop canopy in the summer is higher than for individual seedlings, 4-6%, with a possible crop growth rate of over 15 g-2 day-1. Beddows (1967) quoted Cooper (1967) and MacColl and Cooper (1967) in saying that the highest annual dry matter recorded is 22.6 tons ha-1, corresponding to 2.7% conversion of light energy through the year.

Gregor (1928) found that most plants tested for self-fertilisation set seed in less than 3% of the florets, although one plant produced many more than that. However, Jenkin (1926) observed that the progeny of self-fertilised plants showed a marked lack of vigour.

Caryopses have no after-ripening requirement and can germinate before the endosperm has hardened. Seed falling on the soil surface germinates readily (Beddows, 1967). Surface sowing (called oversowing in New Zealand and Australia and overseeding in the USA) of ryegrass seed to improve pastures or turfs is widely practiced in some countries, and even aerial application of L. perenne seed is not uncommon in New Zealand and possibly elsewhere (Pottinger et al., 1993). Germination in the laboratory reaches 90-95% or more, but this is rarely achieved under field conditions. In one study, seed stored dry in a laboratory only lost viability very slowly over a period of 3 years but after that time viability diminished more quickly: 7- or 8-year old seeds had germination on only 0.7 and 1.3% (Beddows, 1967). Perennial ryegrass is tolerant of salinity levels between 0 and 8 mmhos cm-1 (Cool and Hannaway, 2004).

Hunt and Easton (1989) produced a useful review of research on ryegrass in New Zealand, which includes information on biology, ecology, physiology, cultivation and management from the 1920s onward.

Longevity

Beddows (1967) commented that the potential life-span of plants of L. perenne is not known, but the population in a well-grazed old pasture is apparently ‘ageless’. However, he found that plants from such a habitat grown as spaced plants in a breeding nursery did not survive in a vigorous condition for more than two years and had to be regenerated vegetatively. He suggested that the deterioration may be partly because they were allowed to develop inflorescences and reach the hay stage, but may also be due to root disturbance during cleaning operations. He also questions how the species maintains itself in old pastures, because not all inflorescences are grazed back. In general if flowering is prevented or restricted by spring and summer grazing the plants continue to produce vegetative matter.  

Nutrition

As a source of nutrition for grazing animals, Duke (1983) reported that the green grass contains 26.6% dry matter, 3.0% crude protein, 1.3% fat, 6.7% fibre, 13.2% nitrogen free extract, 2.4% ash (Ca, 0.12%; P, 0.07%; K, 0.51%). The hay contains 12% H2O, 88% DM, 9.2% protein, 3.1% fat, 24.2% fibre, 43.4% nitrogen free extract, 8.1% ash.

Plant Associations

In high quality pastures Trifolium pratense is the clover most closely associated with L. perenne, in the UK, New Zealand and elsewhere. Beddows (1967) lists some of the better known locations of such pastures in the UK. Sheath and Boom (1985) describe how, in New Zealand hill country, as soil fertility and moisture increase, communities move from being dominantly low fertility demanding grasses to associations dominated by these two species. They also form the basis of specialty pastures for today’s booming dairy industry, where diploid or tetraploid plants of L. perenne usually containing improved endophytes are commonly used (DairyNZ, 2013).

Fungal Associations - Endophytes

The endophyte present in ryegrass (Neotyphodium lolii) grows intercellularly as hyaline, sparsely septate hyphae which are present in the leaf sheaths and flowering stems of L. perenne, less so in the leaf blades, and they do not occur in the roots (Menna et al., 2012).

Although ‘wild-type’ endophytic fungi can cause severe grass staggers problems in livestock grazing pastures in Australia, New Zealand and elsewhere (see Economic Impact section), improved endophytes are now being used in L. perenne and these confer resistance to several insect pests without causing serious damage to livestock (Menna et al., 2012; Johnson et al., 2013). Endophytic fungi are only transmitted through infected seed, and the fungus can be killed in the seed by treatment with fungicides, by heat treatment (although this often reduces germination and seedling size), or simply by storage at 5oC or higher for 14 months or more (Rolston et al., 1986). Some authors such as Cunningham et al. (1993) suggested that at least 3 years of storage at room temperature is needed to kill the endophyte.

Besides the toxins responsible for ryegrass staggers and some other disorders in grazing livestock, the endophyte/ryegrass symbiosis also produces toxins that help protect the ryegrass from insect attack. Peramine, for example, is a potent toxin that protects against Argentine stem weevil (Listronotus bonariensis), whilst ergovaline deters feeding by adult weevils and by adult black beetles (Heteronychus arator) (Menna, 2012) (but is also toxic to mammals). Endophyte infected ryegrass also reduced numbers of pasture mealy bug (Balanococcus poae) (Pennell et al., 2005). The natural (‘wild’) endophyte strains in ryegrass can have moderate but inconsistent or transient effects on porina (Wiseana spp.), root aphid (Aploneura lentisci), slugs, and plant parasitic nematodes (Eerens et al., 1998; Jensen and Popay, 2004; Popay et al., 2004; Barker, 2008).

Environmental Requirements

L. perenne is a C3 grass, best suited for growing in temperate climates: its optimum growth temperature is 18-20oC (Mitchell, 1956).   

It is sensitive to drought (Garwood and Sinclair, 1979), which leads to a reduction in herbage production under mild moisture deficit and dormancy or death under severe drought. The inability of perennial ryegrass to survive dry summers in areas where annual rainfall is below 650-700 mm limits its use in Australia (Waller and Sale, 2001). Minimum annual rainfall requirement is 457 to 635 mm (Thorogood, 2003). However, there is some natural variation in drought tolerance in accessions collected from consistently dry habitats, compared with commercial cultivars (Reed et al., 1999). Some perennial ryegrass cultivars can survive drought for 2 years with cutting, but are not as productive as tall fescue. Its roots are able to draw water from approximately 80 cm deep in the soil (Garwood and Sinclair, 1979).  

Perennial ryegrass grows best on fertile, well-drained soils but has a wide range of soil adaptability, and tolerates both acidic and alkaline soils (pH range of 5.2 to 8.0; Cool et al., 2004). It responds well to applications of nitrogen (either as fertiliser N or N fixed by legumes) and phosphorus, and is moderately tolerant of acid soils although there is a sensitivity to aluminium concentration when soil pH is low (pHCa < 4.4) (Waller and Sale, 2001). Nitrogen application has been proposed as a measure to improve persistence of perennial ryegrass in intensively grazed dairy pastures (Harris et al., 1996). In the USA, Sullivan (1992) notes that it is adapted to a wide range of soil types and drainage conditions, including wet or temporarily flooded areas. It can grow in areas up to 2000 m altitude.

Beddows (1967) reported that British varieties are less winter-hardy than those developed elsewhere in Europe, and that cold weather, coupled with wind causes the herbage to lose chlorophyll and turn a pale buff colour. In general, the shorter the vegetation the greener it will remain (Davies and Fagan, 1938; Beddows and Jones, 1958; Beddows, 1967). L. perenne can survive drought periods reasonably well, but this depends on its grazing management before and during the dry period (Beddows and Jones, 1958). It is also tolerant of salt spray and is suitable as a pioneer grass of land with a salt content of up to 0.3%.

Climate

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ClimateStatusDescriptionRemark
Cf - Warm temperate climate, wet all year Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year

Latitude/Altitude Ranges

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Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)
60-65

Notes on Natural Enemies

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Beddows (1967) lists a number of insects and fungi and a virus that attack L. perenne in Europe. They include Melolontha melolantha (Coleoptera), Contarinia lolii (Diptera), Oscinellafrit (fruit fly – Diptera), Ligniera junci (Plasmodiophorales, attacks the roots), Gaeumannomyces graminis (attacks the stem base), Puccinia coronata var. lolii (affects the leaves), Erysiphe graminis (affects the leaves), Rhynchosporium secalis (affects the leaves), Helminthosporium siccans (affects the leaves), Monographella nivalis (affects the leaves), Gibberella zeae (affects the leaves), Laetisaria fuciformis (affects the leaves), Ustilago striiformis (affects the seedheads), Tilletia lolii (affects the seedheads), Claviceps purpurea (affects the seedheads), Gloeotinia granigena (affects the seedheads), and the virus barley yellow dwarf virus (BYDV).

 In New Zealand this nutritious grass has attracted the attention of two native insect species; grass grub (Costelytra zealandica) and porina (Wiseana spp.). Abundance of both species of insect has increased as the grass has become more widely used in pastures. Grass grubs are the larvae of the grass grub beetle; they live in the soil and attack the roots of grasses, often severing the tops of the plants completely so the turf can be peeled back. They generally remain in the ground as larvae from December through to October (although in cooler environments they may be in the ground for nearly two years), with most damage occurring from March onwards. They then pupate in October and November, emerging as beetles to fly, mate and feed. The females lay two or three batches of eggs, usually close to where they emerge, so infestations tend to be localised. The best control in permanent pasture is to do nothing – eventually natural cycles of disease organisms will balance the population which then remains at manageable levels. However, insecticides and biological control agents are available (Zydenbos et al., 2011). Porina is found in southern north island and South Island. The large, unattractive caterpillar causes the damage, emerging from its burrow at night and consuming any vegetation within reach. The larvae pupate around September (depending on species) and the adults emerge mainly in October but some further emergence occurs until February. Females drop eggs whilst flying above pasture, with many but not all dropping eggs close to where they emerged (Zydenbos et al., 2011). Other native pests include manuka beetle (Pyronota spp.) and pasture mealybug (Balanococcus poae). Introduced pests include Tasmanian grass grub (Aphodiustasmaniae), Argentine stem weevil (Listronotus bonariensis), black beetle (Heteronychus arator), root aphid (Aploneura lentisci) and soldier fly (Inopus rubriceps).

The main insect pests of perennial ryegrass in Australia are black field cricket, black headed pasture cockchafer, red headed pasture cockchafer, common army worm, common cutworm, pasture tunnel moth and cereal rust mite (Cunningham et al., 1994). Pasture scarabs and Corbie grubs attack roots just below the ground.

The main fungal pathogens of perennial ryegrass in Australia are crown rust, stem rust, net blotch and blind seed disease (Cunningham et al., 1994). Crown rust can seriously damage perennial ryegrass turf in the Autumn, especially under conditions of low fertility (Meyer and Belanger, 1997). Stem rust and blind seed disease can be serious problems for grass seed production in southern Australia. Blind seed disease reduces seed quality and yield and has cost the Victorian seed industry up to $2.5 million in some years, especially when humidity is high during seed harvest (Cunningham et al., 1994). Barley yellow dwarf virus (BYDV) and ryegrass mosaic potyvirus (RMV) have been reported in perennial ryegrass in Australia (Eagling et al., 1989; Eagling et al., 1992). 

Means of Movement and Dispersal

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Natural Dispersal

Seeds have no special characteristics to aid their dispersal by wind or water. The plants can spread laterally to some extent through tillering, sending up new shoots from the base of the plant.

Vector Transmission

There is little likelihood of seeds of L. perenne travelling far without animal or, more importantly, human intervention.

Grass seeds are capable of germination after passing through the digestive systems of grazing animals such as cattle, sheep (Janzen, 1984; Chambers and MacMahon, 1994; Hulme, 1994; OGTR, 2007)or horses (Campbell and Gibson, 2001; OGTR, 2007). When the potential of cattle to disperse the seeds of perennial ryegrass was assessed by Yamada and Kawaguchi (1972) and Yamada et al. (1972), seeds could be recovered from faeces 12-24 hours after feeding. Viable seeds were recovered and seedlings started to emerge after one week. In a study of seed dispersal by sheep, seeds of Italian and perennial ryegrass were transported in the wool of grazing sheep, and in the case of perennial ryegrass the seeds remained in the wool for 1-2 months (Fischer et al., 1996).  

Accidental Introduction

Due to its widespread global distribution and high productivity it has probably been tested for its ability to grow almost anywhere; making new accidental introductions unlikely.

Intentional Introduction

It is highly likely that perennial ryegrass has mainly been introduced deliberately, as it is widely seen as one of the most valuable pasture species, well known for its palatability, nutritious qualities and growth in many environments. 

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Animal productionCommonly grazed species Yes Yes
Seed tradeCommonly sown species Yes Yes

Impact Summary

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CategoryImpact
Economic/livelihood Positive and negative
Environment (generally) Negative

Economic Impact

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Generally, to the countries to which it has been introduced (and those to which it is native) the benefits of L. perenne as a high-producing pasture and forage species outweigh its negative impacts as an invasive species. New Zealand’s year round grazing systems, and the country’s economy, rely heavily on ryegrass, the seeds of which it grows and exports in substantial quantities. The USA are also major exporters of the seed, producing 8000 MT of perennial ryegrass seed and over 5500 MT of tall fescue seed in 2003-2004 (OGTR, 2013). 

The main negative economic impacts relate to animal toxicity problems associated with L. perenne. These include ryegrass staggers, grass staggers or hypomagnesemia and facial eczema. Occasional nitrate poisoning from ryegrass has been reported when rapid growth of the grass is followed by a period of drought, but in New Zealand reports have mostly referred to tetraploid forms of L. multiflorum rather than L. perenne itself (Connor, 1977).

Ryegrass staggers refers to a seasonal mycotoxicosis of grazing livestock (cattle, sheep, deer, horses, alpacas) characterised by tremors, poor coordination and a staggering gait. This often occurs in Australia and New Zealand and is sometimes seen in Argentina and North America, but is not a major problem in Europe (Menna et al., 2012). Outbreaks in summer and autumn occur only on pasture in which endophyte (Neotyphodium lolii)-infected L. perenne predominates and usually where animals are grazed intensively. Animals recover when moved to different pastures or when rain has promoted new growth. Although the disease was reported in New Zealand before 1906, not until 1981 was its cause shown to be an endophytic fungus which produces secondary metabolites poisonous to livestock – ergovaline and lolitrems. In New Zealand, the wild-type endophyte also causes heat stress and reduced liveweight gains in livestock caused by ergovaline; these effects are a milder form of the toxicosis caused by the endophyte in tall fescue. Even if the endophyte is removed from the grass the plants are then soon killed by insect pests: the endophyte toxins also deterred insect feeding. Following the discovery that peramine, another secondary metabolite was one of the alkaloids responsible for insect deterrence, a large screening effort then ensued (Johnson et al., 2013) to find endophytes less toxic to livestock while retaining the ability to produce insect deterrent alkaloids. Simultaneously endophytes suitable for reducing the toxicity to cattle of tall fescue (Schedonorus arundinaceus, formerly Festuca arundinacea) caused by endophyte infection were also discovered and put into commercial production. (See also Fungal associations – Endophytes above).

A different form of staggers – grass staggers tetany, also known as hypomagnesemia - occurs when livestock do not ingest enough magnesium in their diet. The clinical signs can occur very quickly because the cow does not store magnesium, and is thus reliant on its daily dietary intake. Hypomagnesaemia is most commonly a disease of lactating cows at grass, because grass can be very low in magnesium and the output in milk is high (The Cattle Site, 2013). ‘The increase in disease in spring occurs because rapidly growing grasses, particularly ryegrasses, are very low in magnesium. The cure for affected cattle is an injection of calcium and magnesium, but the problem can be prevented by oral supplementation of magnesium or by dusting the pasture with magnesium oxide.’

Facial eczema, a condition of severe dermatitis in cattle, sheep, and goats, is caused by a toxin in the spores of the saprophytic fungus Pithomyces chartarum. The skin lesions are the secondary result of liver damage, rather than the direct result of the plant toxin. The fungus grows in the moist, protected dead material at the base of forage plants, especially perennial ryegrass. Fungal growth is favoured by warm, wet, humid weather, heavy dew, or irrigation. Intensive grazing practices increase the risk of facial eczema. Relief is brought by moving the animals off the pasture and providing shade, cool water, and a good diet until the liver cells have regenerated and the skin has healed (Oregon State University, 2013).

Ergot is another fungal disease associated with pasture grasses, including perennial ryegrass and tall fescue. The disease is caused by a number of species of Claviceps depending on grass type (eg Claviceps purpurea is associated with perennial ryegrass and tall fescue), and can be toxic to grazing animals and humans (Clarke, 1999). Summer ill-thrift or winter lameness in livestock is associated with ingestion of ergot alkaloids (Harris and Lowien, 2004). Clinical signs include behavioural changes, swelling, lameness, abortions, convulsions, gangrene, and death. In sublethal cases, once the source of ergot is removed, recovery from neurologic signs is likely but recovery from the vascular effects and gangrene is unlikely(OGTR, 2008). 

Environmental Impact

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Impact on Habitats

The perennial ryegrass itself causes minimal direct impact to habitats, but it may contribute to the cumulative damage caused by a large number of invasive grass species. Alone, however, it does affect many different habitats in the State of Victoria in Australia. It is regarded as a high threat weed species in floodplain riparian woodlands in the Highlands-Northern Fall bioregion, as a weed of natural alpine vegetation in north-eastern Victoria, and as a weed of native grassland communities in the south-west of the state (University of Queensland, 2013).

Impact on Biodiversity

University of Queensland (2013) mentions two species native to Australia that are threatened by L. perenne and other invasive grass species. These are the threatened spiny peppercress (Lepidium aschersonii) and the red darling pea (Swainsona plagiotropis). In saltmarsh communities at Lake Beeac, Victoria, Australia the invasion of L. perenne has resulted in the suppression of spiny peppergrass populations (L. aschersonii) and has inhibited the regeneration of this species.

L. perenne is also a principal weed species in endangered tableland basalt forests and fuzzy box (Eucalyptus conica) woodlands in various parts of New South Wales, Australia (University of Queensland, 2013).

In North America, L. perenne does not seem to be regarded as a serious invasive species, but the related species L. multiflorum, sometimes known as L. perenne subspecies multiflorum, is as widespread as L. perenne and is invasive, according to Cal-IPC (2013). However L. multiflorum frequently interbreeds with L. perenne and the hybrids can be difficult to distinguish from the parent species.

Threatened Species

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Threatened SpeciesConservation StatusWhere ThreatenedMechanismReferencesNotes
Lepidium aschersoniiNational list(s) National list(s)Competition - monopolizing resourcesUniversity of Queensland, 2013
Swainsona plagiotropisNational list(s) National list(s)University of Queensland, 2013

Social Impact

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L. perenne is one of the most serious of a large number of grasses that cause hay fever and similar respiratory allergies in humans, largely because it is so widespread in many temperate countries. A human respiratory intake of 1 μg of grass pollen may be sufficient to cause symptoms of hay fever in susceptible individuals (OGTR, 2008).

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
  • 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)
  • Long lived
  • Fast growing
  • Has high reproductive potential
  • Has high genetic variability
Impact outcomes
  • Increases vulnerability to invasions
  • Modification of fire regime
  • Modification of nutrient regime
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Highly likely to be transported internationally deliberately

Uses

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Economic Value

The world-wide economic value of L. perenne is difficult to estimate. New Zealand’s year round grazing systems, and the country’s economy, rely heavily on ryegrass and white clover. In June 2012, pastoral land occupied about 78,883 km2 with stock numbers grazing it being 3.7 million beef cattle, 6.4 million dairy cattle, 31.3 million sheep and 1.1 million deer (Moot et al., 2009; Statistics NZ, 2013). New Zealand also grows and exports substantial quantities of ryegrass seed.

L. perenne is also important to Australian agriculture. Pasture containing perennial ryegrass was estimated to cover an area of 35, 420 km2 (OGTR, 2008). Within Australia in 2003, sales of ryegrass seed for pasture were estimated at 6200 tonnes, with approximately 60% of this being perennial ryegrass (Australian Seeds Authority Ltd., 2006).

Ryegrass seed is also produced in North America and in Europe. The Alberta Agriculture, Food and Rural Development estimated 2003 worldwide seed production for perennial ryegrass at 185,352 megatonnes (MT), the majority in the USA. In 2003/2004, nearly 8000 MT of perennial ryegrass seed and over 5500 MT of tall fescue seed was exported from the USA (OGTR, 2013).

In addition to its use as a forage or hay crop, L. perenne is also extensively used as a lawn or turf grass, with low-slow-growing cultivars high in wild-type endophytes (that give resistance to insect attack) being commonly used for this purpose.

The use of the species as a biofilter for treating aquaculture water discharge has been suggested in the past (Nduwimana et al., 2007). Duke (1983) also suggested it could be used as a source of biomass.

Social Benefit

L. perenne must have had huge social benefits over the years, increasing pastoral production and the populations it supports in many countries. It has also, apparently been casually used in folk remedies for cancer, diarrhea, hemorrhage (Duke and Wain, 1981; Duke, 1983), and malaria (List and Horhammer, 1969; Duke, 1983).

Uses List

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Animal feed, fodder, forage

  • Fodder/animal feed
  • Forage

Environmental

  • Erosion control or dune stabilization
  • Land reclamation
  • Landscape improvement
  • Revegetation
  • Soil conservation
  • Soil improvement

General

  • Ornamental

Similarities to Other Species/Conditions

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L. perenne freely crosses with Lolium multiflorum (Italian ryegrass), producing fertile hybrids (L. x hybridum) with intermediate characteristics. The two species differ primarily in their life span, the former being perennial and the latter being annual or biennial. L. perenne does not have awned lemmas and its new leaves are folded in two when newly emerging from the leaf sheath. Whereas, L. multiflorum has lemmas with fine straight awns up to 10 mm and its new leaves are rolled in the young shoots (Hubbard, 1984). Both species and intermediate forms are widely used in breeding programmes for improved pastures, both short term leys and permanent pasture. 

L. perenne itself shows considerable variation in growth form, from erect, few-tillered individuals to prostrate compact cushions with many vegetative shoots. Beddows (1967) describes several forms with abnormal inflorescences and abnormal spikelet development. L. perenne has also been intensively bred for many years in different countries and many improved varieties of both diploid and tetraploid forms are now available for pasture or turf.

It also forms hybrids with species of Schedonorus (formerly Festuca) such as S. arundinaceus, S. giganteus and S. pratensis. The hybrids are sometimes difficult to identify: for example Edgar and Connor (2010) note that plants of L. perenne with branched inflorescences are probably hybrids between that species and S. arundinaceus. ITIS (2013) places all such hybrids under the name of X Schedolium loliaceum (Huds.) Holub.

Prevention and Control

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Physical/Mechanical Control

L. perenne belongs to a group of perennial grasses that are very difficult to control with flaming. Rask et al. (2011) investigated the use of flame weeding for control of a well-established dense stand of L. perenne ‘Maurice’ in Denmark. They showed that full control can be achieved with flaming, but it depends on the number of treatments as well as the dose of propane. At mean doses above 80 kg propane ha-1 with treatments carried out every second week for a year all weeds were completely killed and no regrowth was seen in the following two weeks.

On a small scale, such as in a garden, perennial ryegrass can be controlled by pulling (if the ground is soft) or by digging. On a larger scale, ploughing by turning the sod or rotary hoeing is often the standard method of destroying a perennial ryegrass crop, sometimes with the aim of renewing the pasture with newer or more appropriate cultivars of the same species.

Biological Control

L. perenne is ideally suited for biological control as there are a large number of insect pests and diseases that can damage or even kill the grass. However, being an extremely valuable and desirable pasture and turf species, biological control is unlikely to be used.

Chemical Control

Treatment of isolated individual plants and of very large areas of perennial ryegrass with glyphosate has been a widely established agricultural practice for many years now. Initial problems with temporary spring-time resistance to the herbicide were overcome with the addition of appropriate surfactants to the herbicide (Bishop and Field, 1987).

DiTomaso et al. (2013) suggest the following herbicides for control of L. perenne in the western USA: aminocyclopyrachlor and chlorsulfuron, clethodim, fluazifop, hexazinone, imazapic, imazapyr, sethoxydim, sulfometuron, as well as glyphosate. Some of these are selective, killing grasses and not broad-leaf plants; others will kill most plants.

However, when using herbicides, care must be taken not to encourage the development of herbicide resistance, which usually arises from repeated use of the same herbicide or of herbicides from the same resistance group. Although only a few cases have been reported, L. perenne has shown resistance to some of the more commonly used herbicides.

In Argentina, resistance to glyphosate has developed in some biotypes of L. perenne where the species is a weed in barley, cropland, soybean, and wheat (Heap, 2013). Glyphosate is a ‘Group G/9’ herbicide, known as glycines (inhibition of EPSP synthase), and L. perenne may be cross-resistant to other Group G/9 herbicides. Positive identification of glyphosate resistant populations has now been found in New Zealand (Ghanizadeh et al., 2013).

Resistance to Group A/1 (ACCase inhibitors) such as clodinafop-propargyl and diclofop-methyl has been found in Chile, where L. perenne is a weed in cereals. In Germany this species first evolved multiple resistance (to two herbicide sites of action) in 2008 and infests wheat. Multiple resistance there has now evolved to herbicides in Groups A/1, and B/2 (ALS inhibitors). These particular biotypes are known to have resistance to iodosulfuron-methyl-sodium, pinoxaden, and pyroxsulam and may be cross-resistant to other herbicides in the Groups A/1, and B/2 (Heap, 2013). In California and Texas, perennial ryegrass growing on roadsides and along railways has developed resistance to sulfometuron-methyl in the B/2 group of herbicides.

IPM

Both Italian ryegrass and perennial ryegrass are good soil stabilizers and therefore are sometimes deliberately seeded with more aesthetically pleasing grasses to aid establishment. However, because both show vigorous seedling growth and thus are very competitive, the ryegrass component in the final stand often needs to be reduced. Close, early mowing following establishment can often inhibit the ryegrasses (Brede and Duich, 1984; Brede and Brede, 1988).

If it becomes necessary in a sports field or other grassed amenity area to remove or replace a dominant species, it is generally common practice to favour the management of the desired grass and persistently overseed this grass, with the expectation that it will eventually crowd out the unwanted grass. As an example, in the conversion of perennial ryegrass golf fairways to Kentucky bluegrass fairways, high seeding of the bluegrass into the mature ryegrass fairway turf followed by low mowing (0.6 cm twice weekly for 4 weeks) allowed for successful establishment of the bluegrass (Kraft et al., 2004).

Control by Utilization

Overgrazing of L. perenne, especially when it is under stress, such as in a dry summer will lead to death of many of the plants and possibly their replacement by other, often weedy grass and herb species.

References

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Agriseeds, 2013. Managing tetraploid perennials. Christchurch, New Zealand: Agriseeds. http://www.agriseeds.co.nz/downloads/Pasture%20management%20-%20managing%20tetraploids%202012.pdf

Anderson MW; Cunningham PJ; Reed KFM; Byron A, 1999. Perennial grasses of Mediterranean origin offer advantages for central western Victorian sheep pasture. Australian Journal of Experimental Agriculture, 39(3):275-284.

Australian Antarctic Division, 2013. Australian Antarctic Data Centre: Biodiversity database. Tasmania, Australia: Commonwealth of Australia. https://data.aad.gov.au/aadc/biodiversity/

Australian Seeds Authority Ltd, 2006. Certified seed produced under OECD, AOSCA and domestic seed certification schemes in Australia in the 12 months to 30 September 2006. Queensland, Australia: Australian Seeds Authority Ltd. http://aseeds.net.au/

Barker GM, 2008. Mollusc herbivory influenced by endophytic clavicipitaceous fungal infections in grasses. Annals of Applied Biology, 153(3):381-393. http://www3.interscience.wiley.com/cgi-bin/fulltext/120735902/HTMLSTART

Beddows AR, 1967. Biological Flora of the British Isles. Lolium perenne L. Journal of Ecology, 55(2):567-87.

Beddows AR; Jones LLI, 1958. Grasses in winter. 1. Observations at Aberystwyth; 2. Suggestions regarding winter herbage. Journal of the British Grassland Society, 13(3):170-6.

Bishop NG; Field RJ, 1987. Controlling perennial ryegrass with glyphosate in spring. In: Proceedings, New Zealand Weed and Pest Control Conference. 194-198.

Brede AD; Brede JL, 1988. Establishment clipping of tall fescue and companion annual ryegrass. Agronomy Journal, 80(1):27-30.

Brede AD; Duich JM, 1984. Initial mowing of Kentucky bluegrass - perennial ryegrass seedling turf mixtures. Agronomy Journal, 76:711-714.

Cal-IPC (California Invasive Plant Council), 2004. Cal-IPC Plant Assessment Form for Anthoxanthum odoratum. Berkeley, California, USA: California Invasive Plant Council. http://www.cal-ipc.org/paf/site/paf/257

Cal-IPC (California Invasive Plant Council), 2013. California Invasive Plants Council. Berkeley, California, USA: California Invasive Plant Council. http://www.cal-ipc.org/

Campbell JE; Gibson DJ, 2001. The effect of seeds of exotic species transported via horse dung on vegetation along trail corridors. Plant Ecology, 157(1):23-35.

Chambers JC; MacMahon JA, 1994. A day in the life of a seed: movements and fates of seeds and their implications for natural and managed systems. Annual Review of Ecology and Systematics, 25:263-292.

Clarke R, 1999. Ergot of pasture grasses. State of Victoria, Department of Primary Industries. Melbourne, Victoria, Australia: The State of Victoria. http://www.depi.vic.gov.au/

Clayton WD, 1973. Flora of Tropical East Africa [ed. by Milne-Redhead, E. \Polhill, R. M.]. London, UK: Crown Agents.

Clayton WD; Vorontsova MS; Harman KT; Williamson H, 2013. GrassBase - The Online World Grass Flora. http://www.kew.org/data/grasses-db/

Connor HE, 1977. The poisonous plants of New Zealand. Second edition. New Zealand Department of Scientific and Industrial Research Bulletin, 99:247 pp.

Cool M; Hannaway DB; Larson C; Myers D, 2004. Perennial ryegrass (Lolium perenne L.). Forage fact sheet. Oregon, USA: Oregon State University. http://forages.oregonstate.edu/php/fact_sheet_print_grass.php?SpecID=6&use=

Cooper JP, 1967. Proceedings 10th International Grasslands Congress, 1966, Helsinki. 715-720 pp.

Council of Heads of Australasian Herbaria, 2013. Australia's virtual herbarium. Australia: Council of Heads of Australasian Herbaria. http://avh.ala.org.au

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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.
Global register of Introduced and Invasive species (GRIIS)http://griis.org/Data source for updated system data added to species habitat list.

Contributors

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11/08/2013: Original text by:

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

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