Quick Facts

Quick facts

• Originally from southern Europe and North Africa, Three-Cornered Garlic (Allium triquetrum) is a bulbous perennial herb with three-angled stems, drooping white flowers with green stripes and a strong onion smell when crushed.
• It grows in moist, poorly drained soils in urban areas, roadsides, pasture and bushland.
• It is not a big problem in improved pastures but can taint milk and meat when consumed by grazing animals.
• In bushland and urban areas it can completely cover the ground in some places.
• Control can be implemented by cultivation and physical removal of all bulbs and/or by chemical means.

What Does It Look Like?

What is it?

Three-Cornered Garlic (Allium triquetrum) is a bulbous perennial herb 100-500 mm high, reproducing by seeds and vegetatively by the production of numerous underground bulblets (a bulb arising from another bulb). The bulbs are almost globose (nearly spherical), small 10–20 mm in diameter, white, with a transparent covering membrane, the outer layers consisting of the swollen base of the leaf sheaths with the numerous smaller bulblets attached. The roots attached to the bulbs are fibrous, shallow and spreading. The stems 100-500 mm are erect, leafy towards the base, triangular in cross-section. The bright green leaves are mostly produced from the base, sometimes limp, rather fleshy, slightly channeled, 150–500 mm long, 5–20 mm wide, and have a strong onion smell when crushed.

The flower buds are initially enclosed in 2 white papery bracts (modified leaves). The bell-shaped drooping flowers are white with green stripes and clustered at the end of the stems.

The round and green fruit is an ovoid capsule ovoid, . 4-6 mm in diameter, and 6–7 mm long, with black oblong seeds. (Hussey et al. 1997; Parsons & Cuthbertson 2001; VicFlora 2016).

For further information and assistance with identification of Three-Cornered Garlic, contact the herbarium in your state or territory.

Flower colour

White

Growth form (weed type/habit)

Herb

Where it currently grows? Preferred habitat

Three-Cornered Garlic favours moist, to poorly drained soils along creek lines and roadsides. It also occurs as a weed of urban areas and pastures (Parsons & Cuthbertson 2001).

Are there similar species?

Three-Cornered Garlic looks similar to the ornamental Snowdrop (Leucojum vernum) but the latter has no green spots on the leaves and no odour.

Why Is It A Weed?

What are its impacts?

Three-Cornered Garlic (Allium triquetrum)  is a weed of urban areas, roadsides pastures (Parsons & Cuthbertson 2001) and a variety of native vegetation. It is  most prominent in wetter shady sites and areas near watercourses (i.e. in riparian vegetation) in South East Australia (Queensland Government 2016).  Three-Cornered Garlic is becoming an increasing problem as a riparian, bushland, roadside and domestic garden weed, as it can soon dominate the ground layer (Muyt 2001; Parsons & Cuthbertson 2001).

Agriculture: Three-Cornered Garlic does not compete strongly with crops and improved pastures, but imparts a strong onion flavour and unpleasant odour to dairy products and meat, making them unfit for sale. It takes about a day of grazing on non-contaminated feed before these taints are lost from milk.

Native ecosystems:  Experience in Victoria has shown that three-cornered garlic can completely replace native ground vegetation in poorly drained soils along watercourses, especially under deciduous trees, growing with introduced perennial grasses or in pure stands that leave soil bare in its summer dormant period (Government of South Australia 2015). 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 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 ground covers and can also seriously impede the regeneration of the over-storey vegetation (Queensland Government 2016).

Urban areas: In urban areas it can invade native and ornamental parkland's, roadsides, abandoned sites and gardens, preferring organic rich soil, to poorly drained heavy soils, also surviving on some poorer soils in some areas.

How does it spread?

Three-Cornered Garlic is spread as bulbs and seed in agricultural produce and in mud sticking to animals, machinery and vehicles. It is also spread in garden refuse and contaminated soil moved during road grading or as garden top dressing (Parsons & Cuthbertson 2001).

What is its history in Australia?

It is not known how, when and why Three-Cornered Garlic initially entered Australia but it was known to be naturalised in South Australia by 1909 (Parsons & Cuthbertson 2001, AVH 2021).

How To Manage It?

Best practice management

Control of Three-Cornered Garlic  (Allium triquetrum) is difficult due to the high number of bulbs and bulblets in the soil. However, chemical and physical / mechanical methods can be used for control, but follow-up over several years is required in most cases.

Chemical control: In a bushland situation Three-Cornered Garlic can be spot sprayed with herbicide just before flowering. In an agricultural situation autumn and spring cultivation kills many plants but must be repeated for several years to ensure that all bulbs have germinated and are killed, effectively removing the area from cropping. A good method is to combine spring or autumn cultivation with spraying just before Three-Cornered Garlic flowers (Brown & Brook 2002; Parsons & Cuthbertson 2001).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au 

Non-chemical control: Physical control: can  be used for single or few outliers, making sure to remove all bulbs. Not effective for larger populations

Mechanical control: Autumn and spring cultivation can be used  to kill plants normally in conjunction with follow-up spraying of chemicals.

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

The bulbs of Three-Cornered Garlic go into dormancy over the summer months with the leaves and above ground part dieing back to ground level, resprout with autumn rains. Flowering stems emerge in late winter/spring and seeds develop in late spring. Seeds germinate in autumn and seedlings grow slowly during winter producing 2 or 4 leaves, the bases of which swell to form a bulb in late winter and spring, the aerial parts dying back in early summer. The seeds and bulbs produced germinate the following autumn (Muyt 2001; Parsons & Cuthbertson 2001).

Where Is It Found?

Which states and territories is it found?

ACT, NSW, SA, TAS, VIC, WA

QLD (formerly naturalised?)

What areas within states and territories is it found?

In ACT, found only in a few locations. 

In New South Wales, Three-Cornered Garlic occurs on the North and Central Coasts, the Western Slopes of the Great Dividing Range and on the South Western Plains of New South Wales.

In South Australia it is common around the Adelaide hills and plains and  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). Also from the higher rainfall areas of the South East (Mount Gambier and surrounds), on Kangaroo Island, and lower Eyre Peninsula.

In Tasmania, it is a common urban weed of the populated areas. It is also scattered in natural and agricultural areas in localised patches around the island, and is a common weed of coastal environment and grasslands in the north-western and southern parts of the state.

In Victoria  it appears in coastal areas, the Dandenong Ranges of Victoria, but also found in many regional areas around towns.

In Western Australia 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 Queensland Government (2016). Common in the wetter lower south-west of Western Australia.(Parsons & Cuthbertson 2001).

It is also previously naturalised in Queensland with only older records from 1958 showing (APC 2021, AVH 2021)

Where does it originate?

Three-Cornered Garlic originates in southern Europe and North Africa.

It occurs commonly in cool to warmer temperate parts of Australia and New Zealand (Parsons & Cuthbertson 2001).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

VIC

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Allium triquetrum

Other scientific names (synonyms)?

Does it have other known common name(s)?

Angled Onion, Three-Cornered Leek, Triquetrous Garlic, Triquetrous Leek