SafePlants

Onion Weed: A Persistent Garden Challenge

Onion weed is a common name applied to several different plant species, often causing frustration for gardeners. This article explores key information about these plants, their characteristics, and management.

Considerations for Pets

• Onion weed has a strong onion-like smell.
• Some onion weed species reproduce from bulbs.

Considerations for Children

• Onion weed has a strong onion-like smell.
• Some onion weed species reproduce from bulbs.

Scientific Names and Common Names

• Several species are commonly called "Onion Weed." This article discusses three prominent ones:
  • Allium triquetrum, also known as three-cornered leek or three-cornered garlic.
  • Nothoscordum inodorum, also known as wild onion.
  • Asphodelus fistulosus, also known as hollow-stemmed asphodel, onion-leafed asphodel, or pink asphodel.

Taxonomy and Nomenclature

• Allium triquetrum:
  • Family: Liliaceae (lily family)
  • Both the English name "three-cornered leek" and the specific epithet "triquetrum" refer to the plant's triangular stem.
• Nothoscordum borbonicum:
  • Synonyms: Nothoscordum gracilis, Nothoscordum inodorum
• Asphodelus fistulosus:
  • Family: Liliaceae
  • Synonym: Asphodelus tenuifolius

Distribution and Habitat

• Asphodelus fistulosus is native to the Mediterranean region.
• Onion weed is prevalent in areas like Wellington, New Zealand, and Western Australia.

Ecological Role

• Onion weed (specifically Asphodelus fistulosus) is considered a noxious weed in many regions, including most of New South Wales and Western Australia, and all of Tasmania, South Australia, and Victoria.
• It is an unpalatable pioneer plant on bare sandy soils.
• It can be difficult to eradicate and may be near impossible to completely kill.

Morphological Characteristics

• Onion weed typically has a strong onion-like smell.
• Leaves:
  • Allium triquetrum has slender, light green, strap-like leaves that sprout in clumps and can grow to around knee height.
  • Nothoscordum gracile has thin strappy leaves and a small white bulb that grows new little bulbs.
  • Asphodelus fistulosus has hollow, somewhat succulent, cylindrical leaves that are 180-400 mm long.
• Flowers: Allium triquetrum has a sweet, dainty snowbell flower.
• Habit: Some species are herbaceous perennials. Asphodelus fistulosus can be an annual or perennial.
• Size: Onionweed can grow to about a foot tall and almost as wide.

Quirky Facts

• Onionweed (likely Asphodelus fistulosus) was once grown as an ornamental plant in Arizona.

Interactions with Other Organisms

• Onions do not compete well with weeds.

Control Methods

• Control can be difficult.
• Digging out the weeds is often ineffective.
• Suggested sprays include Roundup™ (glyphosate) or Amitrole™.
• Selective removal from warm-season grasses may be possible.
• Early season control is important in onion crops.

Further Information

• USDA APHIS Archives
• Collins English Dictionary
• ARKive