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Onion weed

Three-cornered garlic  |  Allium triquetum

Onion weed is a grass like perennial that grows up to 60 cm tall and has a strong garlic smell. It grows from small main bulbs (10–15 mm diameter) and produces offset bulbs.

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What does it look like?

Onion weed is a grass like perennial that grows up to 60 cm tall and has a strong garlic smell. It grows from small main bulbs (10–15 mm diameter) and produces offset bulbs. The fleshy, straight leaves (2–5 per plant) are 20–60 cm long, with white papery sheaths, and usually die back in late spring.
A soft, fleshy, three sided flower stalk grows 20–60 cm high, surrounded by leaves at the base. It supports bell shaped, five petalled flowers that are white with green stripes and appear from October to November. Seed capsules are about 7 mm in diameter and contain black seeds.
Seed and bulbs are spread via water and soil movement, dumped vegetation, contaminated machinery and nursery plants. Sources include wasteland, roadsides, sprayed areas, hedgerows, gardens.

Why is it a problem?

Seeds and offset bulbs ensure distribution. It also tolerates hot and cold, wind, semi-shade, damp heavy soils. It’s intolerant of strong competition for space and heavy shade. It forms dense mats in winter/spring in disturbed sites, discourages native species from establishing.

It’s likely to invade disturbed forest and shrubland, sides of streams, herb fields, bare land, especially after spraying or other clearance to bare land

Control methods

Physical control
Dig out small patches (all year round) and dispose of at refuse transfer station.

Herbicide control
Overall spray using metsulfuron-methyl 600g/kg (3g/10L). Note: Metsulfuron overspray will kill other (desirable) broadleaf plants and has residual activity in the soil which aids in killing below ground parts.

Spraying with glyphosate only gives plant more room to expand. Better to overplant with taller species. In regenerating habitats, often better to leave altogether to minimise disturbance.
CAUTION: When using any herbicide or pesticide, PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.

More information

Also known as “Three-cornered garlic”.

Related links

Onion weed
Onion weed

Taxonomies

FamilyLiliaceae

TypePlants

GroupPerennial

HabitatLand

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