LawnSuite guide: Onion grass in lawns: a bulb weed that flowers in spring
Use this LawnSuite guide to recognise the problem before deciding what to do. Onion grass grows from a small corm under the soil and sets a lot of seed. It's a common lawn weed, and it comes back each year from what's left underground.
How to spot it
Onion grass (Romulea rosea) has very thin, grass-like leaves and small pink-violet flowers. It grows from a corm, a small bulb-like base below the soil surface.
Check which plant you have
Onion weed is a name used for other bulb weeds too. They're different plants, so check which one you have before you act.
When it shows up
Onion grass flowers from August to October. It's a prolific seed producer, so stopping it from setting seed matters.
Lawn care that helps
Dig out small infestations, taking the corm as well as the leaves. Corms and seed travel in soil, so be careful with soil and potted plants you bring in.
If you use a product
Use a selective herbicide whose label lists your turf type and onion grass, and follow the label.
Keep reading
Sources: Australian government and university pages, summarised in our own words.
Not sure it's onion grass?
Create a free LawnSuite account in your browser and photograph the patch. Photo diagnosis uses Google Gemini vision to identify the likely weed, pest or disease and shows a confidence score for each result, so you can match it to the signs on this page before you treat.