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Scientific Name
Common Names
Family
Origin
Naturalised Distribution
Cultivation
Habitat
Distinguishing Features
Habit
Stems and Leaves
Flowers and Fruit
Reproduction and Dispersal
Impacts
Other Impacts
Similar Species
Legislation
Management
Sources
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Click on images to enlarge


large infestation (Photo: Sheldon Navie)


dense infestation in flower (Photo: Sheldon Navie)


habit (Photo: Sheldon Navie)


drooping, strap-like leaves (Photo: Sheldon Navie)


close-up of the three-angled flowering stem (Photo: Sheldon Navie)


flower buds enclosed in two papery bracts (Photo: Sheldon Navie)


close-up of flowers showing the green stripes on their 'petals' (Photo: Sheldon Navie)


older flowers close and begin to droop (Photo: Sheldon Navie)


close-up of older flowers and immature fruit (Photo: Sheldon Navie)


the small onion-like bulbs (Photo: Sheldon Navie)


seedlings (Photo: Sheldon Navie)

Three-cornered garlic
Allium triquetrum

Scientific Name

Allium triquetrum L.

Common Names

angled onion, flowering onion, onionweed, stinking onion, three corner garlic, three cornered garlic, three cornered leek, three-corner garlic, threecorner leek, three-cornered garlic, three-cornered leek, triangular stalked garlic, triquetrous garlic, triquetrous leek, white-flowered onion, wild onion

Family

Alliaceae (Queensland, New South Wales, the ACT and Western Australia)
Liliaceae (Victoria, Tasmania and South Australia)

Origin

Native to north-western Africa (i.e. Algeria, Morocco and Tunisia), the Azores, the Madeira Islands and southern Europe (i.e. Italy, France and Spain).

Naturalised Distribution

A widely naturalised species that is most common in the southern parts of Australia. It is very common in Victoria, Tasmania, south-eastern South Australia and south-western Western Australia. Also scattered in the southern and eastern parts of New South Wales and occasionally naturalised in other parts of South Australia. Three-cornered garlic (Allium triquetrum) was also naturalised in the cooler parts of south-eastern Queensland, but there have been no records in this region for many years.

Naturalised overseas in the UK, western USA (i.e. California and Oregon), tropical Asia and New Zealand.

Cultivation

This species was commonly cultivated as a garden ornamental, but it is not often deliberately cultivated these days.

Habitat

A weed of wetter temperate and cooler sub-tropical regions that favours shaded areas. It inhabits waterways and riparian areas, gardens, parks, footpaths, roadsides, waste areas, disturbed sites, orchards, open woodlands, forests and moist pastures.

Distinguishing Features

Habit

A small, upright (i.e. erect), long-lived (i.e. perennial), herbaceous plant usually growing 18-50 cm tall. Its aboveground parts re-grow each autumn from an underground bulb and die back again during summer.

Stems and Leaves

The slightly fleshy (i.e. semi-succulent) flowering stems grow up to 50 cm long, but are usually only 20-40 cm long. They are triangular in cross-section (i.e. triquetrous), green in colour, and hairless (i.e. glabrous). The stems and leaves give off a rather unpleasant onion-like or garlic-like odour when bruised or damaged.

The leaves are alternately arranged, but clustered towards the base of the stems. They are light green in colour with sheaths that enclose the lower part of the stems. These leaves (12-50 cm long and 3-20 mm wide) are soft, slightly fleshy (i.e. semi-succulent), and often drooping or weeping in nature. They are strap-like (i.e. linear) and have a 'keel' (i.e. prominent midrib) on their undersides. Their margins are entire and they are hairless (i.e. glabrous).

Flowers and Fruit

The flowers are borne in a cluster (3.5-7.5 cm across) at the tips of the stems (i.e. in a terminal umbel). Their buds are initially enclosed in two whitish-coloured papery bracts, which open to reveal a cluster of 3-15 bell-shaped (i.e. tubular) flowers. Each flower is borne on a stalk (i.e. pedicel) 10-25 mm long and they droop towards the ground after opening (i.e. they are pendulous). The flowers (10-15 mm long and 10-18 mm across) have six white 'petals' (i.e. tepals or perianth segments) that are fused together at the base. Each of these 'petals' (10-15 mm long) has a prominent green stripe running down its middle and a pointed or rounded tip (i.e. acute or obtuse apex). The flowers also have six yellow stamens (5-6 mm long) and an ovary topped with a stigma consisting of three short curved branches. Flowering occurs mostly during late winter and spring.

The fruit are rounded (i.e. globular) capsules that are initially green in colour. These capsules (4-7 mm across) turn light brown as they mature and contain several small black seeds (2-5 mm long) that are oblong in shape.

Reproduction and Dispersal

This plant reproduces by seed and also vegetatively by is long-lived bulbs. The small bulbs (5-20 mm across) are egg-shaped (i.e. ovoid) and white in colour. Their outer layers consist of the swollen bases of the leaf sheaths and numerous smaller bulbs (i.e. bulblets or bulbils) are produced from the base of these bulbs each year.

The bulbs and bulblets are spread when soil is moved or cultivated. Seeds may be dispersed by ants, water, in contaminated soil, or in dumped garden waste.

Impacts

Three-cornered garlic (Allium triquetrum) is a significant environmental weed in Victoria, South Australia, Western Australia and Tasmania. This species invades a large number of vegetative formations in the temperate regions of Australia (e.g. dry coastal vegetation, lowland grasslands, grassy woodlands, dry sclerophyll forests, wet sclerophyll forest and freshwater wetlands), but is most prominent in wetter shady sites and areas near watercourses (i.e. in riparian vegetation).

It is known to have serious impacts on the natural habitats that it invades and is very aggressive, having the potential to rapidly occupy large tracts of land. Three-cornered garlic (Allium triquetrum) forms dense and persistent stands that totally dominate the ground-flora when conditions are suitable. These stands crowd out and displace the indigenous grasses and groundcovers and can also seriously impede the regeneration of the over-storey vegetation.

Three-cornered garlic (Allium triquetrum) is probably most widespread in Victoria, where it is regarded as a very serious threat to one or more vegetation formations. It appears very prominently on a plethora of local and regional environmental weed lists in this state (e.g. in Monash City, Knox City, Banyule City, Sherbrooke Forest, Kananook Creek, the Shire of Yarra Ranges, Nillumbik Shire, the Surf Coast Shire, Mitchell Shire, Geelong City, Manningham City, Kingston City, Corangamite Shire, Mornington Peninsula Shire, Colac-Otway Shire, the Goulburn Broken Catchment and the Bendigo region).

It is also a common environmental weed of the Adelaide region in south-eastern South Australia and has been recorded in several conservation areas in this state (e.g. in Marino Conservation Park, Sturt Gorge Recreation Park, Onkaparinga National Park, Belair Reserve, Belair National Park, Anstey Hill Recreation Park and Cleland Conservation Park).

This species favours moist soils around creeklines and granite rocks in south-western Western Australia, and is regarded as a potentially very serious bushland weed in this state. It was given a moderately high priority ranking in the recent Environmental Weed Strategy of Western Australia. In Tasmania, three-cornered garlic (Allium triquetrum) is a common weed of coastal environs and grasslands in the north-western and southern parts of the state. This species is also invasive along creeks in the Sydney region, in New South Wales, and is listed as an environmental weed in the wider Sydney and Blue Mountains region.

Other Impacts

Three-cornered garlic (Allium triquetrum) can also taint milk and meat, however stock tend to avoid it due to its onion-like flavour. Hence, when growing in pastures, it can significantly reduce the productivity of heavily invaded areas.

Similar Species

Three-cornered garlic (Allium triquetrum) may be confused with crow garlic (Allium vineale ), wild onion (Nothoscordum borbonicum ), onion weed (Asphodelus fistulosus ), dune onion weed (Trachyandra divaricata ) and snowdrops (Leucojum aestivum ). These species can be distinguished by the following differences:

Native species such as milkmaids (Burchardia umbellata and Burchardia congesta), garland lily (Calostemma purpureum) and vanilla lily (Sowerbaea laxiflora) may also be confused with three-cornered garlic (Allium triquetrum). However, these species don't smell like garlic and do not have any green stripes on their petals. The petals of milkmaids (Burchardia umbellata and Burchardia congesta) are entirely white, while those of garland lily (Calostemma purpureum) and vanilla lily (Sowerbaea laxiflora) are pink or purple in colour.

Legislation

This species is declared under legislation in the following states and territories:

Management

For information on the management of this species see the following resources:

Sources

Anonymous (2001). Allium triquetrum L. Electronic Flora of South Australia Species Fact Sheet. eFloraSA: Electronic Flora of South Australia. http://www.flora.sa.gov.au. Plant Biodiversity Centre, SA Department for Environment and Heritage, Hackney, South Australia.

Anonymous (2002). A Global Compendium of Weeds. http://www.hear.org/gcw. Hawaiian Ecosystems at Risk Project and Department of Agriculture - Western Australia.

Anonymous (2002). Angled onion. Coast Action/ Coastcare. Coastal Notes. Department of Natural Resources and Environment, State of Victoria.

Anonymous (2002). Australia's Virtual Herbarium. http://www.anbg.gov.au/avh. Australian National Botanic Gardens, Environment Australia, Canberra, ACT.

Anonymous (2006). Allium triquetrum L. Threecorner leek. Plants Profile. http://plants.usda.gov/java/profile?symbol=ALTR4. National Plant Data Center, National Resources Conservation Service, United States Department of Agriculture, Baton Rouge, Louisiana, 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). Angled onion. Environmental Weed Fact Sheet No. 1. http://www.yarraranges.vic.gov.au/Files/1_Fact_Sheet-Angled_Onion.pdf. Shire of Yarra Ranges, Victoria.

Anonymous (2007). Weeds Australia. http://www.weeds.org.au. National Weeds Strategy Executive Committee, Launceston, Tasmania.

Auld, B.A. and Medd, R.W. (1996). Weeds: an illustrated botanical guide to weeds of Australia. Inkata Press, Sydney, New South Wales.

Barker, B., Barker, R., Jessop, J. and Vonow, H. (2005). Census of South Australian Vascular Plants. Fifth Edition. The Botanic Gardens of Adelaide and State Herbarium, Government of South Australia, Adelaide, South Australia.

Blood, K. (2001). Environmental Weeds: a field guide for SE Australia. C.H. Jerram and Associates - Science Publishers, Mt. Waverley, Victoria.

Bostock, P.D. and Holland, A.E. (2007). Census of the Queensland Flora 2007. Queensland Herbarium, Environmental Protection Agency (EPA), Brisbane, Queensland.

Buchanan, A.M. (2007). A Census of the Vascular Plants of Tasmania and Index to The Student s Flora of Tasmania. Web Edition for 2007. http://www.tmag.tas.gov.au/Herbarium/TasVascPlants.pdf. Tasmanian Herbarium, Tasmanian Museum and Art Gallery (TMAG), Hobart, Tasmania.

Ermert, S. (2001). Gardener's Companion to Weeds. 2nd Edition. Reed New Holland, Sydney, New South Wales.

Godden, D.C. (2007). Allium triquetrum 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.

Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds: a guide to the weeds of Western Australia. The Plant Protection Society of Western Australia, Victoria Park, Western Australia.

Keighery, G. and Longman, V. (2004). The naturalized vascular plants of Western Australia. 1: checklist, environmental weeds and distribution in IBRA regions. Plant Protection Quarterly 19: 12-32.

Lamp, C. and Collet, F. (1989). Field Guide to Weeds in Australia. Inkata Press, Melbourne, Victoria.

Lazarides, M., Cowley, K. and Hohnen, P. (1997). CSIRO Handbook of Australian Weeds. CSIRO Publishing, Collingwood, Victoria.

Moore, J. and Wheeler, J. (2002). Southern Weeds and their Control. Department of Agriculture of Western Australia, Perth, Western Australia.

Muyt, A. (2001). Bush Invaders of South-East Australia. R.G. and F.J. Richardson, Meredith, Victoria.

Navie, S.C. (2004). Declared Plants of Australia. CD-ROM. The University of Queensland, St. Lucia, Brisbane, Queensland.

Paczkowska, G. (1994). *Allium triquetrum L. Three-cornered garlic. FloraBase: The Western Australian Flora. http://florabase.calm.wa.gov.au. Western Australian Herbarium, Department of Conservation and Land Management (CALM), Perth, Western Australia.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious Weeds of Australia. Inkata Press, Melbourne, Victoria.

Roy, B., Popay, I., Champion, P., James, T. and Rahman, A. (1998). An Illustrated Guide to Common Weeds of New Zealand. New Zealand Plant Protection Society, Lincoln, New Zealand.

Stanley, T.E. and Ross, E.M. (1989). Flora of South-eastern Queensland. Volume 3. Department of Primary Industries, 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.