Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Anthoxanthum odoratum
(sweet vernal grass)

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Datasheet

Anthoxanthum odoratum (sweet vernal grass)

Summary

  • Last modified
  • 27 September 2018
  • Datasheet Type(s)
  • Invasive Species
  • Host Plant
  • Preferred Scientific Name
  • Anthoxanthum odoratum
  • Preferred Common Name
  • sweet vernal grass
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Monocotyledonae
  • Summary of Invasiveness
  • Anthoxanthum odoratum is a perennial grass of Eurasian origin that has been introduced to much of North America and Australia, and a number of other countries. It is presumed to have been introduced by European...

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Pictures

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PictureTitleCaptionCopyright
Anthoxanthum odoratum (sweet vernalgrass); general habit of flowering plant.
TitleHabit
CaptionAnthoxanthum odoratum (sweet vernalgrass); general habit of flowering plant.
Copyright©Trevor James/Hamilton, New Zealand-2014
Anthoxanthum odoratum (sweet vernalgrass); general habit of flowering plant.
HabitAnthoxanthum odoratum (sweet vernalgrass); general habit of flowering plant.©Trevor James/Hamilton, New Zealand-2014
Anthoxanthum odoratum (sweet vernalgrass); flower heads - (a) terminal florets with exserted stamens (b) florets with exserted stigmas.
TitleFlower heads
CaptionAnthoxanthum odoratum (sweet vernalgrass); flower heads - (a) terminal florets with exserted stamens (b) florets with exserted stigmas.
Copyright©Trevor James/Hamilton, New Zealand-2014
Anthoxanthum odoratum (sweet vernalgrass); flower heads - (a) terminal florets with exserted stamens (b) florets with exserted stigmas.
Flower headsAnthoxanthum odoratum (sweet vernalgrass); flower heads - (a) terminal florets with exserted stamens (b) florets with exserted stigmas.©Trevor James/Hamilton, New Zealand-2014
Anthoxanthum odoratum (sweet vernalgrass); flower heads: (a) florets with stigmas; (b) older head containing seeds
TitleFlower heads
CaptionAnthoxanthum odoratum (sweet vernalgrass); flower heads: (a) florets with stigmas; (b) older head containing seeds
Copyright©Trevor James/Hamilton, New Zealand-2014
Anthoxanthum odoratum (sweet vernalgrass); flower heads: (a) florets with stigmas; (b) older head containing seeds
Flower headsAnthoxanthum odoratum (sweet vernalgrass); flower heads: (a) florets with stigmas; (b) older head containing seeds©Trevor James/Hamilton, New Zealand-2014

Identity

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Preferred Scientific Name

  • Anthoxanthum odoratum L.

Preferred Common Name

  • sweet vernal grass

International Common Names

  • English: buffalo grass; holy grass; large sweet vernal grass; scented vernal grass; sweet vernalgrass; sweet-scent vernal grass; vanilla grass
  • Spanish: alesta olorosa; grama de olor; Pasto oloroso
  • French: flouve odorante; foin d'odeu
  • Chinese: huang hua mao; xiang huang hua mao
  • Portuguese: feno-de-cheiro

Local Common Names

  • Germany: Gemeines Ruchgras; Gewohnliches Ruchgras; Ruchgras; Wohlriechendes Ruchgras
  • Italy: Paglietta odorata; Paleino odoroso; paleo odoroso
  • Japan: harugaya
  • Netherlands: Reukgras
  • Sweden: vårbrodd

EPPO code

  • AOXOD (Anthoxanthum odoratum)

Summary of Invasiveness

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Anthoxanthum odoratum is a perennial grass of Eurasian origin that has been introduced to much of North America and Australia, and a number of other countries. It is presumed to have been introduced by European emigrants in the 18th and 19th centuries, both accidentally and as a pasture plant (although it is now not highly regarded for this purpose). It produces large numbers of seeds which can remain viable for several years, and tolerates a wide range of conditions. It can be a weed of pastures and natural habitats; in parts of Australia it is a threat to some endangered native species. It contains coumarins which in some plant species can be toxic to livestock, and it is listed as a cause of such toxicity, but it is also reported that the concentrations of these compounds are too low to cause problems.

PIER (2013) assessed this species as ‘High Risk’ for Hawaii, because of its rapid spread elsewhere, high seed production and possible toxicity to stock. Cal-IPC (2004) assess it as a Moderate threat to natural habitats in California.

Taxonomic Tree

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

Notes on Taxonomy and Nomenclature

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The Plant List (2010) lists 17 recognised species of Anthoxanthum; between them they are found throughout the world although most species are of limited distribution.

ITIS (2013) lists 10 subspecies and varieties of A. odoratum, but only two are listed as ‘accepted’: Anthoxanthum odoratum ssp. nipponicum (Honda) Tzvelev and Anthoxanthum odoratum ssp. odoratum L..

A related annual species, A. aristatum, originally from the Mediterranean, North Africa and Western Asia, is now naturalized in the United States, Australia, and elsewhere, but is not so widespread as A. odoratum and does not seem to pose so many problems. (See ‘Similarities to Other Species/Conditions’ section).

Description

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(Modified from Clayton et al., 2013)

Habit Perennial; caespitose. Butt sheaths papery; withering. Culms erect, or geniculately ascending; 10–75(–100) cm long; 1–3 -noded. Lateral branches lacking. Leaves mostly basal. Ligule an eciliate membrane; 1–5(–7) mm long. Leaf-blades 1–12(–30) cm long; 1.5–5(–9) mm wide; aromatic. Leaf-blade surface glabrous, or pubescent; hairy on both sides. Leaf-blade apex acuminate.

Inflorescence a panicle. Panicle spiciform; oblong, or ovate; continuous, or interrupted; 1–12 cm long; 0.6–1.5 cm wide. Spikelets solitary. Fertile spikelets pedicelled. Pedicels oblong; 0.5–1 mm long; pubescent.

Fertile spikelets comprising 2 basal sterile florets; 1 fertile floret; without rhachilla extension. Spikelets lanceolate; laterally compressed; 7–9.5 mm long; breaking up at maturity; disarticulating below each fertile floret.

Glumes persistent; dissimilar; exceeding apex of florets; thinner than fertile lemma; shiny. Lower glume ovate; 3.7–5.2 mm long; 0.5–0.6 x length of upper glume; membranous; 1-keeled; 1 -veined. Lower glume primary vein smooth. Lower glume lateral veins absent. Lower glume surface pubescent. Lower glume apex acuminate. Upper glume elliptic; 7–9.5 mm long; 3–5 x length of adjacent fertile lemma; membranous; with hyaline margins; 1-keeled; 3 -veined. Upper glume primary vein smooth. Upper glume surface pubescent. Upper glume apex acuminate.

Florets Basal sterile florets dissimilar; barren; without significant palea; attached to and deciduous with the fertile. Lemma of lower sterile floret oblong; 2.8–3.6 mm long; 1.5–2 x length of fertile lemma; membranous; without keels; 4–5 -veined; pilose; emarginate; awned. Awn of lower sterile floret dorsal; arising 0.6 of way up back of lemma; 2–4 mm long. Lemma of upper sterile floret oblong; 3–3.5 mm long; 1 length of lower sterile floret; membranous; pilose; emarginate; awned. Awn of upper sterile floret dorsal; arising 0.1–0.2 of way up back of lemma; geniculate; 6–9 mm long. Fertile lemma orbicular; 1.7–2.4 mm long; cartilaginous; shiny; without keel; 5 -veined. Lemma lateral veins obscure. Lemma margins convolute; covering most of palea. Lemma apex obtuse. Palea oblong; 1 length of lemma; 1-veined; without keels.

Flower Lodicules absent. Anthers 2; (2.9–)3.5–4.8(–5.5) mm long. Stigmas 2; protogynous; pubescent.

Fruit Caryopsis with adherent pericarp; ellipsoid; 2 mm long. Embryo 0.33 x length of caryopsis. Hilum punctiform.

Plant Type

Top of page Grass / sedge
Perennial
Seed propagated

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

ArmeniaPresentNativeUSDA-ARS, 2013
AzerbaijanPresentNativeUSDA-ARS, 2013
ChinaPresentNativeUSDA-ARS, 2013
-HeilongjiangPresentNativeUSDA-ARS, 2013
-JiangxiPresentNativeeFloras, 2013
-JilinPresentNativeUSDA-ARS, 2013
-LiaoningPresentNativeUSDA-ARS, 2013
-XinjiangPresentNativeUSDA-ARS, 2013
Georgia (Republic of)PresentNativeUSDA-ARS, 2013
IranPresentNativeUSDA-ARS, 2013NW
JapanPresentNativeUSDA-ARS, 2013
KazakhstanPresentNativeUSDA-ARS, 2013
Korea, Republic ofPresentNativeUSDA-ARS, 2013
KyrgyzstanPresentNativeUSDA-ARS, 2013
LebanonPresentNativeUSDA-ARS, 2013
MongoliaPresentNativeUSDA-ARS, 2013
PakistanPresentMissouri Botanical Garden, 2013Baluchistan & N.W.F.P.
SyriaPresentNativeUSDA-ARS, 2013
TaiwanPresentIntroducedeFloras, 2013
TurkeyPresentNativeUSDA-ARS, 2013

Africa

AlgeriaPresentNativeUSDA-ARS, 2013
MauritiusPresentIntroducedUSDA-ARS, 2013
MoroccoPresentNativeUSDA-ARS, 2013
RéunionPresentIntroducedUSDA-ARS, 2013
South AfricaPresentIntroducedUSDA-ARS, 2013
Spain
-Canary IslandsPresentNativeUSDA-ARS, 2013
TunisiaPresentNativeUSDA-ARS, 2013

North America

CanadaPresentPresent based on regional distribution.
-British ColumbiaPresentIntroduced Invasive Allred and Barkworth, 2006; USDA-NRCS, 2013
-New BrunswickPresentIntroducedUSDA-NRCS, 2013
-Newfoundland and LabradorPresentIntroducedUSDA-NRCS, 2013
-Nova ScotiaPresentIntroducedUSDA-NRCS, 2013
-OntarioPresentIntroducedUSDA-NRCS, 2013
-Prince Edward IslandPresentIntroducedUSDA-NRCS, 2013
-QuebecPresentIntroducedUSDA-NRCS, 2013
GreenlandPresentIntroducedUSDA-NRCS, 2013
Saint Pierre and MiquelonPresentIntroducedUSDA-NRCS, 2013
USAPresentIntroducedUSDA-ARS, 2013
-AlabamaPresentIntroducedUSDA-NRCS, 2013
-AlaskaPresentIntroducedUSDA-NRCS, 2013
-ArkansasPresentIntroducedUSDA-NRCS, 2013
-CaliforniaPresentIntroducedUSDA-NRCS, 2013
-ColoradoPresentIntroducedUSDA-NRCS, 2013
-ConnecticutPresentIntroducedUSDA-NRCS, 2013
-DelawarePresentIntroducedUSDA-NRCS, 2013
-District of ColumbiaPresentIntroducedUSDA-NRCS, 2013
-GeorgiaPresentIntroducedUSDA-NRCS, 2013
-HawaiiPresentIntroducedUSDA-NRCS, 2013
-IdahoPresentIntroducedUSDA-NRCS, 2013
-IllinoisPresentIntroducedUSDA-NRCS, 2013
-IndianaPresentIntroducedUSDA-NRCS, 2013
-KentuckyPresentIntroducedUSDA-NRCS, 2013
-LouisianaPresentIntroducedUSDA-NRCS, 2013
-MainePresentIntroducedUSDA-NRCS, 2013
-MarylandPresentIntroducedUSDA-NRCS, 2013
-MassachusettsPresentIntroducedUSDA-NRCS, 2013
-MichiganPresentIntroducedUSDA-NRCS, 2013
-MississippiPresentIntroducedUSDA-NRCS, 2013
-MissouriPresentIntroducedUSDA-NRCS, 2013
-New HampshirePresentIntroducedUSDA-NRCS, 2013
-New JerseyPresentIntroducedUSDA-NRCS, 2013
-New MexicoPresentIntroducedUSDA-NRCS, 2013
-New YorkPresentIntroducedUSDA-NRCS, 2013
-North CarolinaPresentIntroducedUSDA-NRCS, 2013
-OhioPresentIntroducedUSDA-NRCS, 2013
-OklahomaPresent, few occurrencesIntroducedButhod and Hoagland, 2011Prairie hay meadow in McIntosh County in east-central Oklahoma and roadside ditch in Pushmataha County in southeastern Oklahoma
-OregonPresentIntroducedUSDA-NRCS, 2013
-PennsylvaniaPresentIntroducedUSDA-NRCS, 2013
-Rhode IslandPresentIntroducedUSDA-NRCS, 2013
-South CarolinaPresentIntroducedUSDA-NRCS, 2013
-TennesseePresentIntroducedUSDA-NRCS, 2013
-TexasPresentIntroducedUSDA-NRCS, 2013
-VermontPresentIntroducedUSDA-NRCS, 2013
-VirginiaPresentIntroducedUSDA-NRCS, 2013
-WashingtonPresentIntroducedUSDA-NRCS, 2013
-West VirginiaPresentIntroducedUSDA-NRCS, 2013
-WisconsinPresentIntroducedUSDA-NRCS, 2013

South America

ChilePresentIntroducedPIER, 2013

Europe

AlbaniaPresentNativeUSDA-ARS, 2013
AustriaPresentNativeUSDA-ARS, 2013
BelarusPresentNativeUSDA-ARS, 2013
BelgiumPresentNativeUSDA-ARS, 2013
Bosnia-HercegovinaPresentNativeUSDA-ARS, 2013
BulgariaPresentNativeUSDA-ARS, 2013
CroatiaPresentNativeUSDA-ARS, 2013
Czech RepublicPresentNativeUSDA-ARS, 2013
DenmarkPresentNativeUSDA-ARS, 2013
EstoniaPresentNativeUSDA-ARS, 2013
Faroe IslandsPresentNativeUSDA-ARS, 2013
FinlandPresentNativeUSDA-ARS, 2013
FrancePresentNativeUSDA-ARS, 2013
GermanyPresentNativeUSDA-ARS, 2013
GreecePresentNativeUSDA-ARS, 2013
HungaryPresentNativeUSDA-ARS, 2013
IcelandPresentNativeUSDA-ARS, 2013
IrelandPresentNativeUSDA-ARS, 2013
ItalyPresentNativeUSDA-ARS, 2013
LatviaPresentNativeUSDA-ARS, 2013
LithuaniaPresentNativeUSDA-ARS, 2013
MoldovaPresentNativeUSDA-ARS, 2013
MontenegroPresentNativeUSDA-ARS, 2013
NetherlandsPresentNativeUSDA-ARS, 2013
NorwayPresentNativeUSDA-ARS, 2013
PolandPresentNativeUSDA-ARS, 2013
PortugalPresentNativeUSDA-ARS, 2013
-AzoresPresentIntroducedUSDA-ARS, 2013
-MadeiraPresentNativeUSDA-ARS, 2013
RomaniaPresentNativeUSDA-ARS, 2013
Russian FederationPresentPresent based on regional distribution.
-Eastern SiberiaPresentNativeUSDA-ARS, 2013
-Southern RussiaPresentNativeUSDA-ARS, 2013
-Western SiberiaPresentNativeUSDA-ARS, 2013
SerbiaPresentNativeUSDA-ARS, 2013
SlovakiaPresentNativeUSDA-ARS, 2013
SloveniaPresentNativeUSDA-ARS, 2013
SpainPresentNativeUSDA-ARS, 2013
-Balearic IslandsPresentNativeUSDA-ARS, 2013
SwedenPresentNativeUSDA-ARS, 2013
SwitzerlandPresentNativeUSDA-ARS, 2013
UKPresentNativeUSDA-ARS, 2013
UkrainePresentNativeUSDA-ARS, 2013

Oceania

AustraliaPresentIntroducedUSDA-ARS, 2013
-New South WalesLocalisedIntroduced Invasive University of Queensland, 2013In eastern areas and Australian Capital Territory
-QueenslandPresent, few occurrencesIntroducedUniversity of Queensland, 2013South-eastern areas
-South AustraliaLocalisedIntroducedUniversity of Queensland, 2013South-eastern areas
-TasmaniaWidespreadIntroduced Invasive University of Queensland, 2013
-VictoriaWidespreadIntroduced Invasive University of Queensland, 2013
-Western AustraliaLocalisedIntroducedUniversity of Queensland, 2013South-western areas
New ZealandPresentIntroduced Invasive USDA-ARS, 2013
Norfolk IslandPresentIntroducedUniversity of Queensland, 2013

History of Introduction and Spread

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Grant and Antonovics (1978) suggested that A. odoratum colonized the USA from Europe in the late 18th century. The first record in Australia was in Tasmania in 1840 (Council of Heads of Australasian Herbaria, 2013). Along with many other invasive plant species, it was presumably carried to the Americas, Australia and elsewhere by migrants from Europe who travelled to these ‘new’ countries and took with them pasture seeds as well as hay and straw for their animals, straw-filled palliasses and straw and other vegetation as packing material for their belongings. In 1843 the Agricultural and Horticultural Society of Auckland (New Zealand) recommended the importation of A. odoratum as a grass for pastures and by 1870 this species was being sown (Esler, 1987).  Lambrechtsen (1968) reported that he found a record of the species being grown in New Zealand in 1847 and that it then spread rapidly throughout the country.

Risk of Introduction

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A. odoratum has already been spread to many countries where it can grow successfully. It could still be accidentally or deliberately spread further within those countries and to other countries where it has not yet established, but modern phytosanitary precautions at borders should limit the chances of further spread to more countries.

Habitat

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In the British Isles, to which A. odoratum is native, Hubbard (1984) describes it as occurring in a great variety of habitats, often very abundant, on heaths and moors, in hill country grassland, old pastures, meadows and open woodlands. He goes on to say that it occurs on a wide range of soils from sands to clays, and in both wet and dry places.

In North America, where it has been introduced, it grows in meadows, pastures, grassy beaches, old hay fields, waste places, and openings in coniferous forests (occasionally in dense shade) or as a weed in lawns. In southern British Columbia, it is rapidly invading the moss-covered bedrock coastal bluffs and will soon exclude many native species (Allred and Barkworth 2006). Pitcher and Russo (1988) say that it is commonly a weed of pastures, hay fields, roadsides, and ditch banks in the southeastern United States. In Hawaii it is reported as naturalised in pastures, disturbed areas in wet forest, and sometimes subalpine shrubland, at altitudes of 840-2,140 m. (Wagner et al., 1999, in PIER, 2013).

In China, where it is native, its habitat is described as ‘meadows, alpine steppe; 1400–2900 m.’ (eFloras, 2013).

In Australia, where it has been introduced, the University of Queensland (2013) describes the species as commonly a weed of pastures, roadsides, disturbed sites and waste areas in temperate regions of the country. It also invades coastal environs, heathlands, heathy woodlands, grasslands, open woodlands, moist forests, temperate rainforest margins, riparian vegetation, freshwater wetlands, and alpine and sub-alpine vegetation; it is most invasive in moist or low fertility soils in sunny or semi-shaded sites. In New Zealand, too, it is widely distributed on roadsides, waste land, pasture and tussock grassland, in scrub or forest clearings, sometimes in boggy or sandy or rocky, stony ground, from sea level to alpine areas (Edgar and Connor, 2000).

Habitat List

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

Hosts/Species Affected

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In Victoria, Australia, A. odoratum is seen as a threat to the survival of some rare and threatened native ground-cover species. For example, it invades the preferred habitat of wrinkled buttons (Leiocarpa gatesii), a small annual species restricted to a small area. Invasion by this and other weed species is seen as the most serious threat facing the Gorae leek orchid (Prasophyllum diversiflorum), an endangered species known from only six isolated populations (University of Queensland, 2013).

Host Animals

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Animal nameContextLife stageSystem
Bos indicus (zebu)
Bos taurus (cattle)

List of Symptoms/Signs

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SignLife StagesType
Cardiovascular Signs / Tachycardia, rapid pulse, high heart rate Sign
Digestive Signs / Abdominal distention Sign
Digestive Signs / Anorexia, loss or decreased appetite, not nursing, off feed Sign
Digestive Signs / Bloody stools, faeces, haematochezia Sign
Digestive Signs / Melena or occult blood in faeces, stools Sign
General Signs / Dehydration Sign
General Signs / Forelimb lameness, stiffness, limping fore leg Sign
General Signs / Forelimb swelling, mass in fore leg joint and / or non-joint area Sign
General Signs / Generalized lameness or stiffness, limping Sign
General Signs / Generalized weakness, paresis, paralysis Sign
General Signs / Haemorrhage of any body part or clotting failure, bleeding Sign
General Signs / Hindlimb lameness, stiffness, limping hind leg Sign
General Signs / Hindlimb swelling, mass in hind leg joint and / or non-joint area Sign
General Signs / Inability to stand, downer, prostration Sign
General Signs / Internal abdominal mass, swellings, adhesions abdomen Sign
General Signs / Pale mucous membranes or skin, anemia Sign
General Signs / Petechiae or ecchymoses, bruises, ecchymosis Sign
General Signs / Sudden death, found dead Sign
General Signs / Swelling skin or subcutaneous, mass, lump, nodule Sign
Nervous Signs / Dullness, depression, lethargy, depressed, lethargic, listless Sign
Pain / Discomfort Signs / Colic, abdominal pain Sign
Reproductive Signs / Bloody milk, red, pink, brown milk Sign
Respiratory Signs / Dyspnea, difficult, open mouth breathing, grunt, gasping Sign

Biology and Ecology

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Genetics

2n = 20. A. odoratum is almost completely self-incompatible (Borrill, 1963) although a small amount of self-fertilization can occur (Antonovics, 1968). This, combined with prolific seed production (Lambrechtsen, 1968) and rapid turnover of populations (Lambrechtsen, 1968; Antonovics, 1972) means that adaptation of the species to different conditions is often rapid. For example, Snaydon (1970) reported the evolution of specific adaptation and possibly of increased adaptability among populations in less than 40 years and over distances of less than 30 m. Furthermore, Freeland et al. (2010) have established that nutrient additions have resulted in genome-wide divergence (not just in characteristics subject to selection) between experimental plots in the same field over fewer than 75 generations, despite the high potential for ongoing gene flow. This means that A. odoratum can change both phenologically and genetically over a remarkably short time to adapt to local conditions – a reason for its great success as a colonizer of new habitats and as an invasive species.

Reproductive Biology

Lambrechtsen (1968) in his thesis on A. odoratum in New Zealand observed that its seed is light, germinates quickly in light and has no dormancy or only a short dormancy period. The seedlings establish and develop rapidly, with minimal environmental requirements, quickly forming tillers. Flowering was initiated by three months of short-day periods followed by about 10 days at about 5°C. Subsequent emergence of the panicle is influenced by both day length and temperature (Lambrechtsen, 1968).  In the field, the species is often reported as flowering early in the season (Hubbard, 1984; Pitcher and Russo, 1988).

The species is protogynous, the long and feathery stigmata being exserted some time before the anthers, reducing considerably the likelihood of self-fertilisation (Lambrechtsen, 1968). Seed production is copious. Lambrechtsen (1968) recorded about 30,000 seeds per plant, but mentioned that other authors had reported smaller numbers. The same author went on to say that although seeds germinate readily in the light, if buried they can remain viable in the soil for five years or more. Milton (1936), reported in Lambrechtsen (1968), found up to 6.2 million A. odoratum seeds per hectare in fields with swards up to five years old, and up to 11.25 million seeds per hectare in fields with swards more than five years old.

Physiology and Phenology

Harris (1961) showed that A. odoratum seed sown in the field germinated both in autumn and in spring, and even in the next autumn. Most growth of A. odoratum takes place in autumn or early winter and in spring or early summer (Lambrechtsen, 1968). The roots are relatively shallow (Pitcher and Russo, 1988), so plants only absorb nutrients from the upper 10 cm of soil.

A. odoratum is well known for its sweet smell, characteristic of new-mown hay, caused by the organic compound coumarin. Although coumarins in spoilt, mouldy hay containing Melilotus spp. can cause ‘sweet clover disease’ in cattle and sheep, their concentrations in Anthoxanthum species appear to be too low to cause any problems (Davies and Ashton, 1964). These coumarins may play a part in the allelopathic activity of the species -- chemicals produced by its roots inhibit the germination of seed of other species without affecting its own (Scott, 1975). Yamamoto (1995) also considered the allelopathic activity of A. odoratum invading Zoysia grassland in Japan.

Longevity

Plants can live for 3 to 5 years (Lambrechtsen, 1968); Antonovics (1972) suggested that in practice the half-life of a population is about 2 years. However, seeds buried in the soil can last for 5 years or more and large populations can accumulate in seed banks in the soil (Milton, 1936).

Population Size and Structure

In a study of populations of A. odoratum in North Carolina, Grant and Antonovics (1978) found that populations varied from 28 to 99 plants m-2 in a ‘moderate to high population density’ successional old field over a two-year period, with lower densities in a nearby young pine (Pinus taeda) woodland and in the ecotone between them. In the open field, plants were much larger, with more tillers than in the other two habitats. Furthermore the population in the field was made up of older individuals than in the other locations.

Nutrition

A. odoratum seems to be able to grow at low levels of soil nutrients, although the level of nutrition plants require depends on where they were originally grown (Lambrechtsen, 1968).  Thus plants from a montane locality took up decisively different amounts of P and S when compared to plants from four lowland localities.

In the famous Park Grass Experiment at Rothamsted, UK, the long-term fertilizer and liming treatments have caused large differences in soil chemical composition between plots but A. odoratum occurs on almost every plot of the experiment, and therefore grows on soils with widely different contents of N, P, K, Mg and Na, and with soil pH values ranging from 3 7 to 7.5 (Davies and Snaydon, 1973).

Associations

Given the wide variety of habitats in which A. odoratum occurs, it associates with very many other species. It is perhaps most commonly found in pastures or grassland, where it associates with other common grassland species like Lolium perenne, Dactylis glomerata, and Holcus lanatus.

Environmental requirements

A. odoratum is a species of temperate climates that can tolerate a wide variety of habitats, rainfall amounts, soil types and soil nutrient levels.

Climate

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ClimateStatusDescriptionRemark
C - Temperate/Mesothermal climate Preferred Average temp. of coldest month > 0°C and < 18°C, mean warmest month > 10°C

Soil Tolerances

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Soil drainage

  • free
  • impeded

Soil reaction

  • acid
  • alkaline
  • neutral
  • very acid

Soil texture

  • heavy
  • light
  • medium

Special soil tolerances

  • infertile

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Aptinothrips rufus Herbivore
Aspergillus Pathogen
Cerodontha denticornis Herbivore
Chirothrips manicatus Herbivore
Claviceps purpurea Pathogen
Costelytra zealandica Herbivore
Drechslera dematioidea Pathogen
Epichloe typhina Pathogen
Hydrellia tritici Herbivore
Pithomyces chartarum Pathogen
Pratylenchus penetrans Parasite
Puccinia brachypodii Pathogen
Puccinia coronata Pathogen
Puccinia graminis Pathogen
Tilletia anthoxanthi Pathogen

Notes on Natural Enemies

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A. odoratum is presumably susceptible to many of the insects, fungi, nematodes and viruses that attack a wide range of grasses in every country. For example, in New Zealand Lambrechtsen (1968) recorded a few natural enemies of the species, including the fungi Aspergillus sp., Claviceps purpurea, Helminthosporium dematioideum [Drechslera dematioidea], Pithomyces chartarum, Puccinia graminis, Puccinia poae-nemoralis [P. brachypodii], Tilletia anthoxanthi and Epichloe typhina, the viruses cereal yellow dwarf virus and a mosaic virus, and some insects: the leaf-mining flies Cerodontha denticornis and Hydrellia tritici, the thrips Chirothrips manicatus, Chirothrips (?) pallidicornis and Aptinothrips rufus, and the larvae of the beetle Costelytra zealandica.

Means of Movement and Dispersal

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Natural Dispersal (Non-Biotic)

The seeds are light and may be carried a short distance in air currents.

Vector Transmission (Biotic)

Lambrechtsen (1968) said that the long barbed awn and hairy spikelet easily hook onto animals and probably even birds so that animals may contribute markedly to the distribution of A. odoratum seed.

Accidental Introduction

Accidental introduction of the species, probably in hay and straw, must have occurred in the past, but accidental introduction to new countries would probably now be restricted by modern phytosanitary requirements.

Intentional Introduction

In the past this species has been seen as a useful pasture component and although it is not highly regarded at the present time, it might still be deliberately introduced as a possible pasture species.

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Forage Yes Yes
HitchhikerProbably in hay and straw Yes Yes

Impact Summary

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

Economic Impact

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Although A. odoratum has been considered to be a useful pasture plant, Lambrechtsen (1968) reviewed production figures for different species and found that although there was variation in earlier workers’ results, in most cases A. odoratum produced less forage than other pasture plants like Lolium perenne. In pastures and grassland it may replace more valuable plants.

Although A. odoratum contains coumarins, the compounds which in spoilt, mouldy hay containing Melilotus spp. can cause ‘sweet clover disease’ in cattle and sheep, their concentrations in Anthoxanthum species appear to be too low to cause any problems (Davies and Ashton, 1964). On the other hand A. odoratum is mentioned by White (2014) as a cause of such poisoning.

Environmental Impact

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Impact on Habitats

The environmental impact of this species is probably similar to that of any other ‘weedy’ perennial grass. According to Pitcher and Russo (1988) it is not at present seen as a significant threat to Californian Nature Conservancy preserves, but at least in some of those reserves, elimination is the ultimate goal. According to sources cited in Cal-IPC (2013), it invades disturbed areas and prevents re-establishment of native species, but is not observed to completely displace either native or non-native plants, even as a dominant species in heavily invaded areas. In southern British Columbia, it is reported that it is rapidly invading the moss-covered bedrock coastal bluffs and will soon exclude many native species (Allred and Barkworth 2006). In Australia it is often a weed of remnant native grassy vegetation, where it can form dense swards that suppress and replace native groundcover species (University of Queensland, 2013).

Impact on Biodiversity

In Victoria, Australia, A. odoratum is seen as a threat to the survival of some rare and threatened native ground-cover species. For example, it invades the preferred habitat of wrinkled buttons (Leiocarpa gatesii), a small annual species restricted to a small area. Invasion by A. odoratum and other weed species is seen as the most serious threat facing the Gorae leek orchid (Prasophyllum diversiflorum), an endangered species known from only six isolated populations (University of Queensland, 2013). In New South Wales and the Australian Capital Territory, A. odoratum is abundant at two of the three known sites where the Tarengo leek orchid (Prasophyllum petilum) still exists, and considered to be the most serious threat to its survival at one of them.

Threatened Species

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Threatened SpeciesConservation StatusWhere ThreatenedMechanismReferencesNotes
Leiocarpa gatesiiNational list(s) National list(s)VictoriaCompetition - monopolizing resourcesUniversity of Queensland, 2013
Prasophyllum diversiflorumNational list(s) National list(s)VictoriaCompetition - monopolizing resourcesUniversity of Queensland, 2013
Prasophyllum petilumNational list(s) National list(s)New South WalesCompetition - monopolizing resourcesUniversity of Queensland, 2013
Phyllostegia racemosa (kiponapona)NatureServe NatureServe; USA ESA listing as endangered species USA ESA listing as endangered speciesHawaiiCompetition - monopolizing resourcesUS Fish and Wildlife Service, 2001
Speyeria zerene hippolyta (Oregon silverspot butterfly)USA ESA listing as threatened species USA ESA listing as threatened speciesCalifornia; OregonEcosystem change / habitat alterationUS Fish and Wildlife Service, 1998

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Has a broad native range
  • Is a habitat generalist
  • Fast growing
  • Has high reproductive potential
  • Has propagules that can remain viable for more than one year
  • Reproduces asexually
  • Has high genetic variability
Impact outcomes
  • Ecosystem change/ habitat alteration
  • Negatively impacts animal health
  • Reduced native biodiversity
  • Threat to/ loss of endangered species
  • Threat to/ loss of native species
Impact mechanisms
  • Allelopathic
  • Competition - monopolizing resources
  • Poisoning

Uses

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Economic Value

A. odoratum has in the past been regarded as a useful pasture plant, but ceased to be so regarded because of its low productivity and palatability relative to other grasses (Lambrechtsen, 1968). Davies (1925) found that it was grazed by sheep in autumn, winter and early spring but hardly in summer. He considered it not very palatable.

Uses List

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Animal feed, fodder, forage

  • Forage

Materials

  • Essential oils

Medicinal, pharmaceutical

  • Traditional/folklore

Similarities to Other Species/Conditions

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A related annual species, A. aristatum, originally from the Mediterranean, North Africa and Western Asia, is now naturalized in the United States, Australia, and elsewhere, but is not as widespread as A. odoratum (and does not seem to pose so many problems). The University of Queensland (2013) notes that ‘Sweet vernal grass (A. odoratum) is very similar to the relatively rare introduced species A. aristatum, which is only naturalized in some parts of Victoria. However, A. aristatum is a short-lived (i.e. annual) species that does not form large tufts and has relatively loose seed-heads.’ A. aristatum also differs from A. odoratum in being a branched annual with glabrous glumes and awns 4-5 mm long, much longer than the glumes (C. Parker, consultant, UK, personal communication, 2014).

Prevention and Control

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Physical/Mechanical Control

Hand pulling or hoeing is an effective if labour intensive method of control. Mowing before seeds have matured may reduce or delay seed set but if moisture is adequate the plants will regrow and flower again.

Biological Control

Grasses have rarely been successfully targeted in biocontrol activities because too many useful grasses might also be affected. 

Chemical Control

Many herbicides (for example glyphosate) give excellent control of A. odoratum but will also kill other grasses or other species that they contact. Pitcher and Russo (1988) suggest that dalapon could be useful: it kills other grasses, but not broadleaf plants. Dalapon is also recommended in the Florabase database (Western Australian Herbarium, 2013). More modern herbicides like fluazifop-butyl or haloxyfop also kill most grasses without damaging broad-leafed plants. Spot treatment or broadcast spraying with herbicides is possible, but bare areas must be resown with desirable species as soon as possible afterwards.

Grazing

Cattle and sheep readily graze A. odoratum in most seasons, but it may become less palatable in summer, possibly because of higher levels of coumarin (Lambrechtsen, 1968).

References

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Allred KW, Barkworth ME, 2006. Anthoxanthum L. In: Flora of North America, North of Mexico, Volume 24: Magnoliophyta: Commelinidae (in part): Poaceae, part 1 [ed. by Flora of North America Editorial Committee \Barkworth, M. E. \Capels, K. M. \Long, S. \Anderton, L. K.]. USA: Oxford University Press. http://herbarium.usu.edu/webmanual/info2.asp?name=Anthoxanthum_odoratum&type=treatment

Antonovics J, 1968. Evolution in closely adjacent plant populations. V. Evolution of self-fertility. Heredity, 23:219-38.

Antonovics J, 1972. Population dynamics of the grass Anthoxanthum odoratum on a zinc mine. Journal of Ecology, 60(2):351-365.

Borrill M, 1963. Experimental studies of evolution in Anthoxanthum (Gramineae). Genetica, 34:183-210.

Buthod AK, Hoagland BW, 2011. New to Oklahoma: Anthoxanthum odoratum L. (Poaceae). Phytoneuron, 51:1-2.

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

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

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

Davies EG, Ashton WM, 1964. Coumarin and related compounds of Anthoxanthum puelii and Melilotus alba and dicoumarol formation in spoilt sweet vernal and sweet clover hay. Journal of the Science of Food and Agriculture, 15:733-738.

Davies MS, Snaydon RW, 1973. Physiological differences among populations of Anthoxanthum odoratum L. collected from the Park Grass Experiment, Rothamsted. 1. Response to calcium. Journal of Applied Ecology, 10(1):33-45.

Davies W, 1925. The relative productivity of pasture plants. Journal of the Ministry of Agriculture, 32(2):106-116.

Edgar E, Connor HE, 2000. Flora of New Zealand: Vol V, Grasses. Lincoln, New Zealand: Manaaki Whenua Press, 650 pp.

eFloras, 2013. Flora of China. St. Louis, Missouri and Cambridge, Massachusetts, USA: Missouri Botanical Garden and Harvard University Herbaria. http://www.efloras.org/flora_page.aspx?flora_id=2

Esler AE, 1987. The naturalisation of plants in urban Auckland, New Zealand. 1. The introduction and spread of alien plants. New Zealand Journal of Botany, 25(4):511-522.

Freeland JR, Biss P, Conrad KF, Silvertown J, 2010. Selection pressures have caused genome-wide population differentiation of Anthoxanthum odoratum despite the potential for high gene flow. Journal of Evolutionary Biology, 23(4):776-782. http://www.blackwell-synergy.com/loi/jeb

Grant MC, Antonovics J, 1978. Biology of ecologically marginal populations of Anthoxanthum odoratum. 1. Phenetics and dynamics. Evolution, 32(4):822-838.

Harris GS, 1961. The periodicity of germination in some grass species. New Zealand Journal of Agricultural Research, 4:3-4, 253-60.

Hubbard CE, 1984. Grasses, a guide to their structure, identification, uses and distribution in the British Isles (Third edition). Harmondsworth, UK: Penguin Books Ltd, 476 pp.

ITIS, 2013. Integrated Taxonomic Information System (ITIS). Washington, DC, USA: Smithsonian Institution/NMNH. http://www.itis.gov/

Lambrechtsen NC, 1968. Some aspects of the biology of Anthoxanthum odoratum L. Christchurch, New Zealand: University of Canterbury. http://ir.canterbury.ac.nz/bitstream/10092/5664/1/lambrechtsen_thesis.pdf

Milton WEJ, 1936. Investigations on the improvement of hill grazings. III. The buried viable seeds of enclosed and unenclosed hill land. ABERYSTWYTH. Welsh Plant Breeding Station Bull. Ser. H, No. 14:58-86.

Missouri Botanical Garden, 2013. Tropicos database. St Louis, USA: Missouri Botanical Garden. http://www.tropicos.org/

PIER, 2013. Pacific Islands Ecosystems at Risk. Honolulu, Hawaii, USA: HEAR, University of Hawaii. http://www.hear.org/pier/index.html

Pitcher D, Russo MJ, 1988. Element Stewardship Abstract for Anthoxanthum odoratum: Sweet Vernal Grass. Arlington, Virginia, USA: The Nature Conservancy, 9 pp. http://www.invasive.org/gist/esadocs/documnts/anthodo.pdf

Scott D, 1975. Allelopathic interactions of resident tussock grassland species on germination of oversown seed. New Zealand Journal of Experimental Agriculture, 3(2):135-141.

Snaydon RW, 1970. Rapid population differentiation in a mosaic environment. I. The response of Anthoxanthum odoratum populations to soils. Evolution, 24:257-69.

The Plant List, 2010. The Plant List Version 1. UK: Royal Botanic Gardens, Kew and Missouri Botanical Gardens. http://www.theplantlist.org/

University of Queensland, 2013. Weeds of Australia, Biosecurity Queensland edition. Queensland, Australia. http://keyserver.lucidcentral.org/weeds/

US Fish and Wildlife Service, 1998. In: Big Island II: Addendum to the Recovery Plan for the Big Island Plant Cluster. US Fish and Wildlife Service, 80 pp. + appendices.

US Fish and Wildlife Service, 2001. In: Revised Recovery Plan for the Oregon Silverspot Butterfly (Speyeria zerene hippolyta). US Fish and Wildlife Service, 121 pp.. http://ecos.fws.gov/docs/recovery_plan/010822.pdf

USDA-ARS, 2013. Germplasm Resources Information Network (GRIN). Online Database. Beltsville, Maryland, USA: National Germplasm Resources Laboratory. https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch.aspx

USDA-NRCS, 2013. The PLANTS Database. Baton Rouge, USA: National Plant Data Center. http://plants.usda.gov/

Wagner WL, Herbst DR, Sohmer SH, 1999. Manual of the flowering plants of Hawaii. Revised edition. Honolulu, Hawaii, USA: University of Hawaii Press/Bishop Museum Press, 1919 pp.

Western Australian Herbarium, 2013. FloraBase. Australia: Western Australian Herbarium. http://florabase.dec.wa.gov.au/

White ME, 2014. Consultant: a diagnostic support system for veterinary medicine. Ithaca, New York, USA: Cornell University College of Veterinary Medicine. http://www.vet.cornell.edu/consultant/

Yamamoto Y, 1995. Allelopathic potential of Anthoxanthum odoratum for invading Zoysia-grassland in Japan. Journal of Chemical Ecology, 21(9):1365-1373. http://link.springer.com/article/10.1007%2FBF02027568

Contributors

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09/04/13: Original text by:

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

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