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 weed 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.

21 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

  11. This advice is very encouraging re onion weed, so I will start slicing and starving it. But what about the oxalis, wandering jew, convolvulus, kikuyu that are creeping in from neighbouring properties and taking over at least 1/2 of our 2/3 acre block?? Should I just move?

    They say the way to remove wandering jew is to move house and not take any plants with you but, seriously, all perennial herbs can be eliminated without herbicides by depriving them of the means to make energy for growth. They all need light to photosynthesise which converts carbon dioxide into glucose for energy. Cutting them off at growth level will deprive them of the ability to grow. With creeping weeds such as convolvulus, wandering jew and kikuyu, this method works very well: Lawn into garden
    Chooks love wandering jew. If this weed has become invasive, fencing off the affected area with some chicken wire, and putting chooks in the area for a few days will clear this weed. – Lyn

  12. Thanks for info. I was wondering how to tree the situation when onion weed is growing after you mulch on top of the mulch????!!!!
    You may have to cut off the foliage at ground level several times, Sarah, before the bulbs are weak enough not to produce new growth. – Lyn

  13. hi everyone…. just joined and hoping someone can help out with a small problem. On my property , there is now a large amount of onion grass growing down on the river flats. The soil is quite good but nothing has been grown on this land in the last 25 years. i have had all sorts of weeds growing over the years ,now it is the onion grass’s turn. Is there any way that i might be able to get rid myself cide of this stuff, without resorting to herbicide. Thanks
    Hi Jimbo, if you keep mowing the area as short as possible so that the weeds can’t photosynthesise you will get rid of it (but it won’t happen overnight). The weed needs green foliage to convert CO2 into energy for growth. If you have a very large area covered with onion weed, you obviously can’t cover it with black plastic but continually depriving it of the opportunity to grow will kill it off. Trying to dig it out only spreads it. – Anyone else, any suggestions? – Lyn

  14. It took years to get rid of onion grass around my azaleas. Now I want it back. It was keeping lace bugs off my azaleas. I didn’t know. Now my azaleas,which have been here 50 yrs. are dying. I don’t know where to get some.
    Barbara, pest attack is merely a symptom that plants are stressed because conditions are not to their liking. Onion grass prefers soils of low fertility. Do you feed your azaleas? Do they have adequate water to allow them to absorb the nutrients they need? If your azaleas started dying after the onion grass was removed, how did you remove the onion grass? Did you dig it out or use a herbicide?
    To get rid of the azalea lace bugs, use a horticultural soap spray. These are potassium-based and different from ordinary soap sprays, which can burn plant leaves. As well as killing the bugs, the potassium ingredient also strengthens cell walls, helping plants to resist pest attack. Natrasoap is one brand you can use, and Yates also have a horticultural soap spray. – Lyn

  15. Irene I have just used Round up on my Onion Grass which is under my Roses brought in by planting a potted plant given me by a friend !!!. But having read all your comments on shearing the onion grass i will change to that method and just hope I havent done any damage to my Roses might be a bit of a fight with getting under the Roses but well worth it by all your comments Will let you know how I go !!!

    Hi Irene, glyphosate binds to soil particles until broken down by soil bacteria. It reduces plants’ uptake of Manganese, Zinc, Iron and Boron, which are necessary for disease-resistance. Keep a close watch on your roses for signs of disease, and keep them well-watered so that they are not stressed over summer. An application of organic mulch (kept clear of rose stems) will help soil bacteria to get busy as well as preventing any new growth from the onion weed being able to photosynthesise. – Lyn

  16. Thank you so much. This is very informative. Most other websites just say to dig them out with lots of soil around to prevent small bulblets falling off, but from my experience it is a losing battle and simply not possible without disturbing the roots of nearby plants. I will try cutting above ground portion.

    Daiva, you will have to be persistent cutting off any signs of foliage to exhaust the plant, but it is the only way to get rid of it when it is among plants. – Lyn

  17. I would like to thank you Lyn Because I also have masses of onion weed in my lawn I have just brushed them with straight weed killer But next week I will cut it all down to ground level many thanks June

    You will probably have to cut it several times, June, until the plants have exhausted the carbohydrates stored in the bulbs, but I heard on a gardening show at the weekend that weedkiller applications have to be repeated too, to kill them off. Give your lawn a good feed of a complete fertiliser (not just nitrogen) and don’t mow it too short. A strong, healthy lawn chokes out this weed. – Lyn

  18. I’m looking to buy a 6 hectare property that’s full of onion weed, I’ve identified it as romulea rosea. I want to produce grazing pasture for horses. As not one to like the use of strong herbacides would elevating soils ph and seeding rye clover be enough to eradicate this weed?

    Hi Kaye, the post I’ve written is for onion weed, in which I accidentally wrote ‘onion grass’ in one place. I apologise for that. The weed you have is different and, as onion grass is often found growing on limestone ground, raising the soil pH won’t help eradicate onion grass. Perhaps this website may help with your problem: Onion grass

  19. I struggled with onion weed for many years – making the problem worse – in a large garden in Perth. Now we are in Melbourne and a few years ago I dug over a section of the nature strip with the result that I disturbed the bulblets (didn’t know they were there) and now I have a massive onion weed problem in that area. I dug out some of them and put the bulbs in a bucket full of water to be left for three weeks to make onion tea, as I’ve read that if you pour this on the active plants it will kill them… any thoughts on this? Additionally I go out every day with kitchen scissors and cut them off at ground level – am astonished at how quickly they can grow. Interestingly they are now making flower heads at ground level or just below ground level (I cut these off as well). I’m wondering at which point It will be safe to dig the ground over again. I plan on incorporating gypsum and compost as the ground is pretty hard, then getting rid of the couch grass which is thin on the ground in winter and lets in lots of weeds, then planting buffalo grass.

    Replacing couch with buffalo sounds like a good plan, Ann. The gypsum and compost sounds an even better idea because these weeds thrive in soils with poor nutrition. Healthy lawns will out-compete them. If you don’t have enough compost, an application of complete organic fertiliser each spring will keep your lawn growing strongly. Don’t cut your lawn too short as this reduces the area of foliage grass needs to photosynthesise to create the carbohydrates used for energy, and weakens the roots. It might be a good idea to check your soil pH too, as the soil pH controls the availability of nutrients to plants. – Lyn

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