Click on images to enlarge
large infestation (Photo: Forest and Kim Starr, USGS)
infestation (Photo: Sheldon Navie)
habit (Photo: Sheldon Navie)
habit (Photo: Sheldon Navie)
base of plant, with tufts of leaves and several upright stems (Photo: Sheldon Navie)
close-up of old leaves and young growth at the base of a plant (Photo: Sheldon Navie)
upper part of stem, with leaves and young seed-heads (Photo: Sheldon Navie)
mature seed-heads (Photo: Sheldon Navie)
leafy bracts of a mature seed-head (Photo: Sheldon Navie)
close-up of seeds being dispersed (Photo: Sheldon Navie)
Schizachyrium microstachyum, and emerging weed species in south-eastern Queensland, can be easily be confused with whisky grass (Photo: Sheldon Navie)
Andropogon virginicus L.
Gramineae (South Australia)Poaceae (Queensland, New South Wales, the ACT, Victoria, Tasmania, Western Australia and the Northern Territory)
Native to North America (i.e. south-eastern Canada, eastern USA and Mexico), Central America (i.e. Belize, Costa Rica, Guatemala, Honduras, Nicaragua and Panama), the Caribbean and tropical South America (i.e. Colombia).
Widely naturalised in eastern Australia (i.e. in south-eastern Queensland, eastern New South Wales and some parts of Victoria). It was also naturalised in the ACT, but has not been collected there for many years.
Also naturalised in New Zealand, Hawaii and beyond its native range in south-western USA (i.e. California).
a long-lived tufted grass usually growing 0.5-1 m tall.
the older stems and leaves turn reddish-brown or brownish-orange in colour during summer.
its elongated leaves (10-40 cm long and 2-5 mm wide) can be either flat or folded.
its flower-spikelets fall off entire at maturity, usually with numerous long white silky hairs.
Stems and Leaves
The leaves consist of a hairy to hairless (i.e. pubescent to glabrous) leaf sheath, which partially encloses the stem, and a spreading leaf blade. These leaf blades can be either flat or folded (10-40 cm long and 2-5 mm wide) and are hairless except for some long (i.e. pilose) hairs that are occasionally found towards the base of their upper surfaces. Where the leaf sheath meets the leaf blade there is a small membranous structure topped with hairs (i.e. a ciliate ligule).
Flowers and Fruit
The leafy seed-heads are long and narrow and consist of several to numerous pairs (occasionally triplets or quadruplets) of tiny branches (i.e. racemes). Each pair of branches (2-3 cm long) is partly enclosed by brownish or bronze-coloured leafy bract (i.e. spathe) 2.5-6 cm long. The stalks of these branches are very slender and they bear several flower spikelets among clusters of long white hairs (5-10 mm long). The flower spikelets are arranged in pairs, with one of the flower spikelets in each pair being stalkless (i.e. sessile) and the other being borne on a short stalk (i.e. pedicel). The stalkless or sessile spikelet (2.5-4 mm long and about 1 mm wide) has both male and female parts (i.e. it is bisexual and fertile), while the stalked or pedicellate spikelet is sterile and is sometimes absent entirely (i.e. only a stalk is present). The stalkless spikelets consist of a pair of bracts (i.e. glumes) and two tiny flowers (i.e. florets), only one of which is fully formed. The fully formed floret has only one obvious floral bract (i.e. a lemma) that is topped with a delicate and straight awn (1-2.5 cm long), three stamens, and an ovary topped with a two-branched feathery stigma. flowering occurs from autumn through to summer (i.e. from March to December).
Reproduction and Dispersal
This species reproduces mainly by seed. These light seeds may be easily spread by wind and water and can also adhere to animals, clothing and vehicles. They are also commonly dispersed to new areas when seeding plants are slashed or mown, and can also move longer distances in contaminated soil and agricultural produce.
Whisky grass (Andropogon virginicus) is regarded as an environmental weed in New South Wales and Queensland. This species invades open woodlands, grasslands, forests and other native vegetation in eastern Australia. However it prefers very open sunny areas and is particularly common along tracks and roadsides. Unlike many exotic weeds, it is also known to invade native plant communities that are extremely deficient in nutrients. Whisky grass (Andropogon virginicus) is highly flammable at certain times of the year and can significantly alter the fire regime in areas where it invades. It is also known to affect other ecosystem-level functions (e.g. it lowers soil evaporation and causes accelerated erosion).
This species is currently of most concern in eastern New South Wales, where it is seen as a threat to the integrity of several plant communities and the survival of some rare and threatened species. It appears on numerous local and regional environmental weed lists in New South Wales (e.g. in the wider Sydney and Blue Mountains region, in the North Coast, Central Coast and South Coast regions, and in the Warringah, Manly, Pittwater and Byron Councils) and also occurs in several conservation areas in this state (e.g. Warriewood Wetlands,
The "invasion of native plant communities by exotic perennial grasses" was recently listed as a "key threatening process" in New South Wales, and whisky grass (Andropogon virginicus) is one of the species specifically mentioned in this listing. Whisky grass (Andropogon virginicus) is also mentioned as being a significant threat or principal weed species in eucalypt grassy forest/woodlands of the New England Tableland bioregion and swamp sclerophyll forests on coastal floodplains, both of which are endangered ecological communities in New South Wales.
Grassy weeds, such as whisky grass (Andropogon virginicus), are also degrading the habitat occupied by the vulnerable Charmhaven apple (Angophora inopina) and may be having a direct impact on the regeneration of this species. It has also been recorded as a weed threat at some of the sites occupied by the vulnerable downy wattle (Acacia pubescens) in the Sydney region.
In Queensland, whisky grass (Andropogon virginicus) is mainly a problem in the south-eastern corner of the state. It is ranked among the top 200 most invasive plant species in this region and has been recorded in conservation areas on the Gold Coast (e.g. in the Pimpama
Overseas, whisky grass (Andropogon virginicus)
Overseas, whisky grass (Andropogon virginicus)is also a serious problem in Hawaii and parts of mainland USA. It is common and often dominant along roadsides and in disturbed dry to mesic forests and shrublands in Hawaii. It also forms continuous cover in boggy, open mesic or dry habitats in the USA. These dense stands persist as a result of competition and allelopathy, and provide excellent fuel for fires, which further stimulate its invasion. Studies in mainland USA have found that both fire intensity and area of land burnt are higher in areas where whisky grass (Andropogon virginicus) occurs.
Because this species is of low nutritional value to livestock, it can reduce the productivity of invaded pastures. It may also be a fire hazard (i.e. it can increase the damage caused by bushfires).
Whisky grass (Andropogon virginicus) is very similar to the native firegrass (Schizachyrium fragile) and the recently introduced Schizachyrium microstachyum. However, these grasses have their seed-head branches (i.e. racemes) borne singly instead of in pairs.
It may occasionally also be confused with grader grass (Themeda quadrivalvis ) and the native kangaroo grass (Themeda triandra), which also turn reddish-brown in colour. However these species have their flower spikelets arranged in drooping triangular-shaped clusters, with very large and twisted awns.
This species is not declared or considered noxious by any state or territory government in Australia.
For information on the management of this species see the following resources:
- the Whisky grass page on the South Coast Weeds website at http://www.esc.nsw.gov.au/Weeds/index.asp.
Anonymous (2003). Downy Wattle (Acacia pubescens) Recovery Plan. NSW National Parks and Wildlife Service, Hurstville, New South Wales.
Anonymous (2006). Andropogon virginicus L. Broomsedge bluestem. Plants Profile, The Plants Database. http://plants.usda.gov/java/profile?symbol=ANVI2. National Plant Data Center, National Resources Conservation Service, United States Department of Agriculture, Baton Rouge, Louisiana, USA.
Anonymous (2006). Andropogon virginicus L., Poaceae. Pacific Island Ecosystems at Risk (PIER): plant threats to Pacific ecosystems. http://www.hear.org/Pier/species/andropogon_virginicus.htm. Institute of Pacific Islands Forestry, Hawaii, USA.
Anonymous (2006). Germplasm Resources Information Network (GRIN). http://www.ars-grin.gov/cgi-bin/npgs/html/index.pl. National Germplasm Resources Laboratory, National Genetic Resources Program, Agricultural Research Service (ARS), United States Department of Agriculture (USDA), Beltsville, Maryland, USA.
Anonymous (2006). National List of Naturalised Invasive and Potentially Invasive Garden Plants. Version 1.2. World Wildlife Fund - Australia (WWF Australia).
Anonymous (2007). Charmhaven Apple - profile. NSW National Parks and Wildlife Service, Department of Environment and Climate Change, Sydney, New South Wales.
Anonymous (2007). Invasion of native plant communities by exotic perennial grasses - key threatening process listing. NSW National Parks and Wildlife Service, Department of Environment and Climate Change, Sydney, New South Wales.
Batianoff, G.N. and Butler, D.W. (2002). Assessment of invasive naturalized plants in south-east Queensland. Plant Protection Quarterly 17: 27-34.
Bostock, P.D. and Holland, A.E. (2007). Census of the Queensland Flora 2007. Queensland Herbarium, Environmental Protection Agency (EPA), Brisbane, Queensland.
Jacobs, S.W.L. and Wall, C.A. (2007). Andropogon virginicus L. New South Wales Flora Online. PlantNET - The Plant Information Network System of Botanic Gardens Trust. http://plantnet.rbgsyd.nsw.gov.au. Royal Botanic Gardens and Domain Trust, Sydney, New South Wales.
Lepschi, B.J., Adams, L.G., Mallinson, D.J. and Jones, D.L. (2007). Census of the Vascular Plants of the Australian Capital Territory. http://www.anbg.gov.au/cpbr/ACT-census/. Centre for Plant Biodiversity Research, Canberra, ACT.
Sharp, D. and Simon, B. (2002). Ausgrass: an interactive key to Australian grasses. CD-ROM. Queensland Herbarium, Brisbane, Queensland.
Walsh, N.G. and Stajsic, V. (2007). A Census of the Vascular Plants of Victoria. Eighth Edition. National Herbarium of Victoria, South Yarra, Victoria.
Wheeler, D.J.B., Jacobs, S.W.L. and Whalley, R.D.B. (2002). Grasss of New South Wales. 3rd Edition. University of New England, Armidale, New South Wales.