Allium triquetum

Onion weed

Also known as:

Three-cornered garlic

Family: Liliaceae

Origin: Mediterranean

White flowers of the onion weed.
A pungent herb that has white onion-like bulbs and bright green leaves. Stems have a unique triangular shape that is noticeable when you hold it.
Photo credit: Jonathan Boow

Regional Pest Management Plan (RPMP) status

  • Not a legally declared pest

View more about the RPMP statuses

General description

Perennial herb < 60 cm tall. Bulbs are white, < 2 cm in diameter and ovoid, with smaller bulblets produced from the base. Stems are three-angled. Leaves are linear, fleshy, alternate and have a prominent underside midrib. Stems and leaves give off a strong garlic smell when crushed. Flowers are white with green stripes down petal centres, tubular, pendulous and borne on stems in October-November. Seed capsules are round, < 7mm in diameter, green maturing to brown and contain black seeds.

What you need to know

Although onion weed is not a legally declared pest plant, it may still be invasive in some situations. Consider lower-risk alternatives for your garden, such as native plants.


Riparian, forest and shrubland margins, open areas, disturbed sites, wasteland, roadsides.


Seeds are dispersed by water, ants and soil movement. Vegetative spread from bulbs or bulblets. Human-mediated dispersal through dumping of garden waste and movement of contaminated soil and machinery.

Impact on environment

Can form dense infestations, displacing native vegetation and suppressing seedling recruitment.


Site Management

Follow up treated areas each year. Encourage natural regeneration of native plants or replant treated areas where possible after 2-3 treatments to establish dense ground cover and minimise reinvasion. In regenerating habitats it is often best to leave it to minimise disturbance.

Recommended approaches

Physical control

Method: Dig out.

Plant parts requiring disposal: Seeds and bulbs.

Disposal options: Small amounts can be rotted in a covered water barrel and bulbs can be crushed. Remove to greenwaste or landfill.


Biocontrol is currently not available for this species.

Community agrichemical control recommendations

Certified Handler/Experienced agrichemical user: Foliar spray with 3g metsulfuron-methyl per 10L and 20ml penetrant.

Caution: When using any herbicide or pesticide please read the label thoroughly to ensure that all instructions and safety requirements are followed.

Onion weed in flower.
A common home garden invader that is able to quickly spread and take over a garden or lawn. Small white flowers produce viable seed that can spread by water and ants.
Photo credit: Jonathan Boow