What is this onion-style weed?

[denu]

This is a problem for

 

me and I have not been able to identify it and then eradicate it.

[EricL]

Hello @denu 

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about the weeds in your garden.

What you have there appears to be a young onion weed (also known as Nothoscordum or Allium triquetrum, depending on the species). The key identifiers are: A small bulb at the base (often reddish or brown). Thin, grass-like leaves or stems that can have a slight onion smell when crushed. White roots coming from the base. It grows from a small bulb, which makes it persistent and hard to fully eliminate if bulbs are left in the soil. 

This weed is common in gardens and lawns across Australia and spreads easily through both seeds and underground bulbs. To manage it, try to dig it out carefully with the bulb intact, breaking the bulb off and leaving it in the soil will allow it to regrow.

Due to its resilience, it is very difficult to supress and control. For a direct approach, I suggest using Yates 1L 490g/L Zero Weed Killer Super Concentrate in conjunction with Yates Zero Weeding Herbicide Applicator Brush. It is a non-selective herbicide which kills everything on contact, make sure to apply only to the weeds and be mindful of accidental drips and spills. Please make sure to wear personal protection such as gloves, goggles and a mask when using chemicals in your garden.

If you need further assistance, please let us know.

Eric

[denu]

Thanks Eric for the information, you have included a lot of detail.

However it is not “onion weed” of this I am certain. I am very familiar with onion weed and have successfully removed it previously, there  is no doubt in my mind that this is not onion weed. Onion weed smells like onion, whereas this thing has no odour and the bulb is a different colour to onion weed.

  

thanks for your contribution 

[MitchellMc]

Hi @denu,

What you've pulled up does look similar to onion weed in terms of structure: slender leaves, elongated white stems, and small rounded bulbs with fine fibrous roots. Even though you're not noticing an onion smell, that can fade in some species or be hard to detect in younger plants.

It's worth noting there are a few lookalikes (such as Romulea or Triteleia) that also grow from bulbs and mimic the grass-like appearance of onion weed. However, from a control perspective, they behave the same way — spreading via bulbils and resisting typical surface-level weeding.

So, whether it's onion weed or a very close cousin, the eradication method remains the same. Carefully dig them out with the entire bulb attached, or spot-apply a non-selective herbicide, such as Yates Zero, using a brush or wand applicator to avoid collateral damage.

If flowers appear, that can help lock in a definitive ID — feel free to share more photos if they do.

Please let me know if you have any questions.

Mitchell

[denu]

Thanks Mitchell, will persevere with your advice..

[denu]

Hello again, more information for you, these things have never developed flowers nor appeared that they would. And they do not resemble in any way the linked examples you provided.

cheers

[MitchellMc · Accepted solution]

Thanks for the extra detail @denu. I understand the frustration when a persistent weed doesn’t quite match the usual suspects, but having looked again at your photos, I’d still say this plant shares a lot of key features with onion weed and its close relatives. Below is a picture of Romulea. Both grow from small white bulbs, have slender, grass-like leaves, and fine fibrous roots — it’s this structure that makes them difficult to eradicate. 

Even if it’s not classic Nothoscordum or Allium triquetrum, the way it spreads and resists removal suggests a bulbous weed from a similar family or ecological niche. Some variants or related species don’t always flower reliably, especially if they’re mown or disturbed regularly. 

I guess it really comes down to whether you want a positive ID or if you want to remove it. Removal will be the same as any other bulbous weeds; remove as much of the bulb and surrounding bulbils as possible, or carefully apply herbicide to target the base. However, if you are looking for an ID, that might not be possible unless they have other attributes that could be considered.

Let me tag our resident horticulturalist @Noelle to see if she has any thoughts.

Mitchell

[Noelle]

Hi @denu 

In my opinion, your weed is Onion Grass (Romulea rosea) - not Onion Weed (also known as Angled Onion - Allium triquetrum) which has a wider leaf, white flowers like snow drops and smells like an onion.

To control Onion Grass, it's necessary to ensure that any weedkiller is taken up by the bulbs - the leaves are very fine so there's not a lot of surface area for the absorption of regular herbicide applications. However, persistence over a period of time will eventually kill the bulbs and bulbils. Direct injection of a weedkiller solution (eg Roundup diluted to one part of herbicide to 6 parts of water by volume) physically injected into bulbs is usually effective.