Onion weed

Onion weed (Nothoscordum inodorum) seems to cause problems for quite a few gardeners who are unsure about organic ways to be rid of this pest. I did cover onion weed previuosly in a post on perennial weeds but, as it is a common problem, it might be worth covering it separately.
It is fairly easy to eradicate it from lawns, by keeping grass growing vigorously. Healthy lawn grass will out-compete onion grass in a fairly short time and no other treatment is necessary. In fact, onion weed in lawns is merely a sign that your lawn needs a bit more TLC.
Onion weed in garden areas is an entirely different problem. Because onion weed is a perennial weed, it stores nutrients and carbohydrates in its bulbs to generate growth in the following season, in the same way as spring bulbs such as daffodils. Trying to pull out or dig up these weeds in garden areas results in the parent bulbs releasing tiny bulbs (bulbils) from the base of the main bulb. These grow into mature plants, and all the digging has achieved is multiplication of the problem.
To get rid of onion weed, you have to prevent the bulbs storing food for growth. Onion weed can also produce seed. Cutting off the foliage at ground level will prevent the plants making carbohydrates in their leaves, and also prevent seed forming.
In an unused garden area, you can do this by slashing, or mowing, the foliage to ground level, then covering the area with black plastic for several months. Anchor the edges of the plastic with planks, bricks or whatever you have to prevent it blowing away. Deprived of moisture and the sunlight that enables it to store carbon dioxide as carbohydrates (photosynthesis), the bulbs will weaken and die. Avoid using clear or light plastic, as these will still allow the plants to photosynthesize and, in some conditions, they can actually improve weed growth.
In garden beds that are being used, onion weed is more difficult to eradicate because the bulbils can be released whenever you disturb the soil. Cut off the foliage at ground level with shears to prevent it making food for the bulbs. Then mulch the beds with 5–7 cm of mulch. You may have to cut back foliage several times as soon as it appears. If you do this consistently, bulb growth will become progressively weaker, and you will eliminate the problem without disturbing the soil and stimulating the growth of more bulbs.
When you have a chance to leave a particular bed lying fallow, you can give the bed the black plastic treatment. Onion weed is more commonly found in undernourished soils, or where soil pH is unsuitable for healthy plant growth. Where onion weed has been a problem, check your soil pH, and improve organic matter content in soil to prevent the problem recurring.

12 thoughts on “Onion weed

  1. We have a lot of onion weed in our paddocks and after watching flocks of galahs scratching and feeding on it ,I’ve used my chooks to dig it out and eat it .They love it as much as the galahs . In our hard cracking clays the small bulbs are just under the surface . They eat most of the other pasture as well but their manure makes up for it ..Probably harder to put the chooks through a garden bed unless you put them in a dome pen and move it around .

  2. Hey everyone!
    I am new to aussieorganicgardening.com.
    Hope I can be a regular here!

  3. …Or… you can treat it as a veggie and eat it!
    Onion weed is fantastic stuff, sort of like a cross between onion & garlic. It’s a great addition to all sorts of meals, and even makes fantastic fritters when dunked in batter & fried. You can even eat the flowers. And eating it is a surefire way to get rid of lots of it, unfortunately!
    Since discovering how tasty this stuff is I treasure it – it’s no longer considered a weed in this house.

  4. I seem to have crops of what I call onion weed in my rose garden. They start as tiny very thin shoots that eventually grow to a flat leafed weed about 20cm to 30cm long. They have a bulb and smell like onions and I can’t get rid of them. I haven’t had any flowering, and am generally confused as there seems to be 2 or 3 different weeds that are called “onion weeds”. Certainly mine are not big enough to eat, so how to rid of them?
    You are correct Joni – there are several weeds that are commonly called onion weeds, and the best way to get rid of the ones in beds that contain plants is to keeping cutting off the foliage at ground level. If they can’t make carbohydrates, they can’t grow and they can’t produce bulbils. The bulbs will gradually weaken and die off. – Lyn

  5. in our community garden where nothing is growing bare sandy soil very small pebbles supplyed by the council is where onion grass is growing but not sure if it is onion weed has puple floers doesnt grow to high its like a grass can some one send photos of onion weed young & mature extra

  6. Pingback:   Onion weed problems by Aussie Organic Gardening

  7. hey im into finding uses for weeds such as medical and for food does anyone have info
    Matthew, it is not a good idea to self medicate with any plants as the strength of the active ingredients can vary greatly with the growing conditions and it can be easy to overdose. As far as using weeds for food – Jackie French’s book Organic Control of Common Weeds contains a section on edible weeds. – Lyn

  8. Hi, I’m new to this site and would like to thank you for the great advice about onion grass. Thanks!

  9. Hi, I’ve just joined and that is mainly due to your advice on how to eradicate onion grass – having a problem with it at the moment and your solution is ever so simple. Have a nice day all and catch your later…..:)

  10. l have had more and more onion weed each yr and this yr now that the tops have died off the pods have come 2 the surface, so lm getting out as many as possible and are going 2 put some in pots and some in2 another garden bed where its hard 2 get anything 2 grow…… l cant wait 2 put in2 my food and l will be cutting off leaves and putting in2 freezer 4 off season….lve had them on pizza be4 and they are delishes.

    It is unwise to recommend eating weeds based on their common name only. Onion weed (Nothoscordum inodorum) is a member of the onion family but is often confused with Onion grass (Romulea rosea), also know as Guildford grass, which is a member of the Iris/Crocus family and produces bulbs what we, as children, called puddings. This plant has no onion smell or nutritional value, and I would not recommend eating it. It also reduces crop production in garden beds, and the treatment is the same as that for onion weed. Incidentally, Jackie French does not include onion weed in the edible weeds section of her book. – Lyn

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